E FR
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THE BIGGEST NAME IN ASTRONOMY
OF TH E TH WI OP O N G SC M I N IC A AG OT IM ROB A
HOW TO WATCH, IMAGE AND LISTEN TO METEORS
Sky at Night GLOWING
GHOSTS
Discover the beauty and science of planetary nebulae
COLLECTING THE COSMOS Tips from the experts on starting a space memorabilia collection
SWITCH OFF STRAY LIGHT Line your telescope to banish reflections
RAINBOWS ON VENUS Probe sees peculiar pattern in its final days
INSIDE THE 12
PLANETBEST NEBULA ARY OBSERV E TO E MONTHTHIS
ALSO IN THIS ISSUE 1ST FOR GEAR 100º field of view: Altair’s new Hyperwide eyepiece
BIG DATA DELUGE The all-sky surveys that push the boundaries of computing
OPEN CLASSROOM Are free online courses the right way to learn about astronomy? AUGUST 2014 #111 www.skyatnightmagazine.com
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LETTER FROM THE EDITOR AUGUST 03
Welcome
This month’s contributors include... PAUL F COCKBURN SCIENCE WRITER Paul learns how astronomers are dealing with the massive amounts of data being generated by sky surveys. Page 62 JON CULSHAW IMPRESSIONIST Jon’s imagination takes him back in time as he hunts down a METI signal in this month’s Exoplanet Excursions. Page 21 WILL GATER ASTRONOMY AUTHOR
Will unravels the mysteries of planetary nebulae, the glittering carcasses of long-dead stars like our Sun. Page 30 ELIZABETH PEARSON STAFF WRITER
Our staff writer looks into the different ways you can study astronomy without taking up fulltime education. Page 40
Join the robotic imaging revolution Cast your mind back to our March 2014 issue and you’ll remember that in it we ran a feature all about robotic scopes. In ‘Imaging from afar’, we looked at four robotic scopes that are accessible online and to everyone regardless of skill, budget... or cloud cover. Your response to this feature was very positive and so this month we’re delighted to be able to offer every one of you the chance to do a month’s free imaging with a robotic telescope located at one of the world’s major observatories, the Observatorio del Teide on Tenerife, where the seeing and dark sky are near-perfect for astronomy. Turn to page 29 to take up this exclusive offer, which is running in partnership with the Bradford Robotic Telescope. This month there’s another exciting astronomical event with the return of the yearly Perseid meteor shower. This year’s is marred slightly since peak activity coincides with a bright gibbous Moon, but don’t be put off: brighter trails can still be seen through the lunar glare and, on page 78, we explain how to make the most of visual observations. You should have no trouble imaging them if you know the processing tools that can rescue shots of meteor trails set against a Moon-
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soaked sky. For a refresher on these invaluable techniques, turn to page 60. And even if it’s cloudy, meteor observations are still possible – using radio to listen for them. On page 73 we explain how to do just that using nothing more complex than the FM radio on your kitchen windowsill. Enjoy the issue.
Chris Bramley Editor
PS Next issue goes on sale 21 August.
Sky at Night LOTS OF WAYS TO ENJOY THE NIGHT SKY...
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In the magazine
NEW TO ASTRONOMY? See The guide on page 78 and our online glossary at www.skyatnightmagazine.com/dictionary
ON THE COVER 30
73
29
68 81
30
THE GLOWING GHOSTS
73
LISTENING IN
106
36 94 62
40
FEATURES
REGULARS
06 Eye on the sky
10 Bulletin 17 What’s on 19 A passion for space
29 EXCLUSIVE READER OFFER Sign up for one month’s free remote access to the Bradford Robotic Telescope in Tenerife
30 The glowing ghosts COVER: NASA/ESA/C. ROBERT O’DELL (VANDERBILT UNIVERSITY) AND DAVID THOMPSON (LBTO), THIS PAGE: THINKSTOCK, WWW.THESECRETSTUDIO.NET
Discover the secrets of planetary nebulae. Plus – we point out 12 you can see in the night sky this month.
Sky at Night presenter Maggie Aderin-Pocock considers what makes our local star unique.
21 Jon Culshaw
40 Opening the classroom
Jon’s off-world travelogue continues.
Learning astronomy has never been easier – we profile the best alternatives to full-time study.
22 Interactive
62 Dealing with the deluge
24 SUBSCRIBE
Find out how astronomers are dealing with the vast amounts of data generated by today’s pro scopes.
Get your issues at a discount
68 Collecting the cosmos
26 Hotshots
Three space memorabilia experts share their secrets on starting a collection of your own.
73 Listening in Learn how to tune your radio to pick up meteors entering our atmosphere ahead of the Perseids peak.
skyatnightmagazine.com 2014
47 THE SKY IN AUGUST Your 15-page guide to the night sky featuring the top sights, an all-sky chart, a deep-sky tour and more…
90
FIRST LIGHT
78 Skills 78 The guide The basics of meteor observing.
81 How to Flock a Newtonian telescope.
85 Sketching 87 Scope Doctor
89 Reviews First Light 90 Sky-Watcher Heritage 100P Tabletop Dobsonian.
94 Altair Lightwave Hyperwide 100° eyepiece.
98 AstroHutech Hinode SG solar autouider.
102 Books 104 Gear
106 What I really want to know is… What can a ‘rainbow’ tell us about Venus?
Download the complete multimedia experience with our special edition apps THE APOLLO STORY The Apollo Story is your complete guide to the greatest journey in human history, featuring the facts, figures and stories from every Apollo mission. In this app: X GO BEHIND THE SCENES WITH AUDIO AND VIDEO SECTIONS X RARE PHOTOS AND EXHAUSTIVE PICTURE GALLERIES Download your copy today for just £4.99/$6.99!
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Forged in
flames More than a beautiful astrophoto, this image challenges what we thought we knew about star clusters A cluster of bright stars, appearing purple in X-ray light, burst from the centre of the Flame Nebula, NGC 2024, in this composite image. While NASA’s Chandra provided the X-ray images for the composition, Spitzer was responsible for the infrared data coloured red, green and blue. Astronomers are using the image to readdress their ideas on star formation, as it appears that the stars on the outskirts of the cluster are older than those in the middle. It’s thought that stars form into clusters when vast clouds of gas and dust condense, the centre of the cloud pulling in material until star formation is triggered. As this process occurs at the centre of a cluster first, it has always been presumed that the stars in this area are the oldest. There are still numerous theories as to how this most recent observation occurred and astronomers will now study other young star clusters to try and replicate their findings.
NASA/CXC/SAO; OPTICAL: DETLEF HARTMANN; INFRARED: NASA/JPL-CALTECH
CHANDRA X-RAY OBSERVATORY AND SPITZER SPACE TELESCOPE 7 MAY 2014
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A curious site X CURIOSITY ROVER 13 MAY 2014
(ARIZONA STATE UNIVERSITY) AND Z. LEVAY (STSCI), ESA/HUBBLE & NASA, NASA/JPL-CALTECH/SPACE SCIENCE INSTITUTE
NASA/JPL-CALTECH/MSSS, NASA/ESA/H. TEPLITZ AND M. RAFELSKI (IPAC/CALTECH) A. KOEKEMOER (STSCI) R. WINDHORST
NASA’s Curiosity rover inspects the site of a previous experiment in this remarkably high-resolution image. The target, a 1.6cm-wide hole in a sandstone rock called Windjana, is a fine example of the level of precision afforded by the rover’s instruments. The perfectly linear series of black dots within were created by Curiosity’s ChemCam laser; the plasma released in these blasts was analysed to determine the rock’s composition.
W Scouring the spectrum HUBBLE SPACE TELESCOPE 17 JUNE 2014 The Hubble Ultra Deep Field has become an advert for the space scope’s power. This latest image includes the addition of ultraviolet light. It’s hoped this will give astronomers a better view of star formation in the 10,000 or so galaxies captured in the frame.
skyatnightmagazine.com 2014
EYE ON THE SKY AUGUST 09
S Cosmic curves HUBBLE SPACE TELESCOPE, 2 JUNE 2014 Two vast, symmetrical arms enclose the intensely bright nucleus of spiral galaxy NGC 1566 in this image from Hubble. Belonging to the Seyfert class of galaxies, renowned for having very active and luminous centres, NGC 1566 lies in the constellation of Dorado and is the brightest member of the Dorado galaxy group.
W Planetary neighbourhood watch CASSINI SPACECRAFT, 1 MAY 2014 It may look familiar, but in this image the blue orb floating above Saturn’s F Ring is not planet Earth but the gas giant Uranus. Thanks to the predominance of methane and lack of clouds in Uranus’s atmosphere, its marine blue hue is still clearly visible from a distance of over 4.2 billion km.
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Bulletin The latest astronomy and space news written by Hazel Muir
PLUS
CUTTING 13 CHRIS LINTOTT 15 LEWIS DARTNELL
EDGE
Our experts examine the hottest new astronomy research papers
COMMENT by Chris Lintott
Hybrid star
The hybrid may be able to give us some new insights into stellar interiors
finally found JOHN R. FOSTER/SCIENCE PHOTO LIBRARY, NASA/JPL-CALTECH, NASA/GODDARD SPACE FLIGHT CENTER/ARIZONA STATE UNIVERSITY/BROWN UNIVERSITY, NRAO/AUI/NSF
The star could be the first object of a type theorised decades ago A NEW TYPE of hybrid star has been discovered in the Small Magellanic Cloud decades after it was first theorised. The star is believed to be a Thorne-Zytkow object; a neutron star trapped inside a red giant or supergiant. The hybrids were first theorised by physicist Kip Thorne and astronomer Anna Zytkow in 1975. They are believed to form when one star in a binary pair goes supernova and collapses to form a neutron star, disrupting its orbit and causing the two stars to collide and merge. Until now, such hybrids have been completely theoretical. The discovery was made by a team of researchers who have been examining the spectra of red supergiants using the 6.5m Magellan Clay telescope at Las Campanas Observatory in Chile. The spectrum of HV 2112 in the Small Magellanic Cloud, however, had a strange composition. The
team discovered signs of the elements rubidium, lithium and molybdenum within the spectra. All of these elements can be found in most stars, but the high levels suggest an unusual chemistry within the star. Later analysis found that the spectra was consistent with what is expected from a ThorneZytkow object, though there are still a few minor inconsistencies that need working out. “Studying these objects is exciting because it represents a completely new model of how stellar interiors can work,” says Emily Levesque of the University of Colorado Boulder, who led the project. “In these interiors we also have a new way of producing heavy elements in our Universe. You’ve heard that everything is made of ‘star stuff’—inside these stars we might now have a new way to make some of it.” > See Comment, right
It’s apparent that HV 2112 is having an exciting time. Deprived of support from the nuclear fusion that sustains normal stars, the outer layers of the red supergiant must have started to collapse. The enormous gravitational pull of the neutron star will have added to the pressure, and gas just above its surface will be at a temperature of a billion degrees, hotter than the cores of all but the most massive stars. These enormous temperatures drive nuclear reactions of their own, producing the exotic spectral signature astronomers have now detected. These reactions are probably not enough to make the hybrid star stable for the long term. Either the neutron star will gain enough mass to collapse as a black hole, or the outer star will run out of material and end up as nothing more than a disc around an otherwise normal neutron star. Whatever happens, it’s fabulous to observe one of these elusive objects in the wild. CHRIS LINTOTT co-presents The Sky at Night
BULLETIN AUGUST 11
Moon’s origins become more certain Lunar rocks confirm that the young Earth suffered a giant impact NEW STUDIES OF lunar rocks have strengthened the view that the Moon was formed following a collision between the Earth and a Mars-sized body around 4.5 billion years ago. Planetary scientists suspect that a body called Theia slammed into the young Earth, creating the debris that coalesced into the Moon. It’s been suggested the Moon would have formed mostly from Theia and thus should have a different composition to Earth – but previous research has
indicated that Earth and Moon are surprisingly similar. Now Daniel Herwartz from Göttingen University in Germany and colleagues analysed lunar samples gathered during the Apollo missions using refined techniques – discovering that the oxygen isotope levels within are indeed significantly different to those on Earth. “We can now be reasonably sure that the giant collision took place,” says Herwartz. www.uni-goettingen.de
A collision could have created debris that then formed into the Moon
NEWS IN
BRIEF DARK MATTER GLUES GAS CLOUD A vast cloud of hydrogen hurtling towards the Milky Way seems to be packed with dark matter, the invisible, unidentified substance that makes up most of the Universe’s mass. Observations by the Green Bank Telescope in West Virginia suggest the cloud would otherwise have fallen apart on a previous journey through our Galaxy. “An object like this simply shouldn’t survive the trip,” says Matthew Nichols from the Sauverny Observatory in Switzerland, who concludes that dark matter’s gravity ‘glues’ it together.
STAR WILL GOBBLE TWO PLANETS
DID LIFE THRIVE ON A MARTIAN VOLCANO? THE SLOPES OF a giant Martian volcano once covered in glacial ice may have been home to one of the most recent habitable environments found so far on Mars. Arsia Mons is the third tallest volcano on Mars and one of the largest mountains in the Solar System. Now Kat Scanlon from Brown University in Rhode Island and colleagues have analysed landforms surrounding the volcano and shown that eruptions happened along its northwest flank around 210 million years ago, the same time that a glacier covered the region. The heat from those eruptions would have melted massive amounts of ice to form englacial lakes – bodies of water within the glacier, like liquid bubbles in a half-frozen ice cube. The ice-covered lakes held hundreds of cubic kilometres of meltwater. “This is interesting because it’s a way to get a lot of liquid water very recently on Mars,” says Scanlon, adding
Þ Arsia Mons in false colour; the fluvial channels, inset, may be the result of meltwater from glacial deposits that the site would be a good target for future Mars landers looking for signs of past life. www.brown.edu
Two alien worlds orbiting a star that lies 2,800 lightyears away are set to become a snack of cosmic proportions. Their host star, Kepler 56, is swelling into a red giant, and astronomers have calculated that it will swallow the two planets in 130 million and 155 million years respectively. “This is the first time two known exoplanets in a single system have a predicted time of death,” says team leader Gongjie Li from the Harvard-Smithsonian Center for Astrophysics in Massachusetts.
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NEWS IN
BRIEF
The magnetic fields accompanying black holes are much stronger than previously assumed
ROCKY ‘GODZILLA’ PLANET FOUND An exoplanet first spotted by NASA’s Kepler spacecraft has turned out to be a curious type dubbed a ‘mega-Earth’. Follow-up observations suggest it is 17 times as massive as Earth, yet surprisingly it is a rocky world rather than a gas giant despite its large mass. “This is the Godzilla of Earths,” says team member Dimitar Sasselov from the Harvard-Smithsonian Center for Astrophysics in Massachusetts. He adds that the planet is 11 billion years old, proving that rocky planets could form in the distant past, even when heavy elements were scarce in the Universe.
Black holes have
mighty magnetism
ALEXANDER TCHEKHOVSKOY/LBL, DAVID A. AGUILAR (CFA)
AMATEURS TO TAKE CONTROL OF NASA CRAFT NASA has agreed to let citizen scientists contact – and if possible, control – one of its a defunct spacecraft. Under the deal, private firm Skycorp will help amateurs reach International Sun-Earth Explorer 3, launched in 1978 to study the solar wind; NASA has no plans to use it again. If the technical details are ironed out, work with the spacecraft could start in August. “We have a chance to engage a new generation of citizen scientists through this creative effort,” says John Grunsfeld from NASA’s headquarters in Washington DC.
skyatnightmagazine.com 2014
Their magnetic fields can stop gas clouds from plunging into the dark voids MAGNETISM PLAYS A surprisingly powerful role in the environment surrounding supermassive black holes. A new study has shown that the behemoths, which lurk at the centres of most large galaxies, have magnetic fields strong enough to counteract their enormous gravitational pull. These supermassive black holes are millions or billions of times as massive as the Sun. They also have strong magnetic fields that energise jets of zooming particles that sprout out into space. A theory developed by Alexander Tchekhovskoy from the Lawrence Berkeley National Laboratory in California suggests that a black hole’s magnetism might be strong enough to balance gravity. In other words, the two forces would cancel out, so that a cloud of gas just beyond the black hole’s ‘point of no return’ would be spared the pull of gravity and instead levitate in place. Now astronomers have found the first direct evidence for that in a study of more than 70 black holes. Archived observations of black hole jets made by the Very Long Baseline Array, a network of radio telescopes
in the US, allowed the team to estimate their magnetic fields accurately. “We realised that the radio emission from black holes’ jets can be used to measure the magnetic field strength near the black hole itself,” says team leader Mohammad Zamaninasab, who carried out the study while at the Max Planck Institute for Radio Astronomy in Bonn, Germany. The team found that a black hole’s magnetic field can produce forces on matter that are as strong as those resulting from its gravity. The magnetic fields are similar in strength to those created by MRI scanners in hospitals – around 10,000 times greater than Earth’s magnetic field. “The magnetic fields are strong enough to dramatically alter how gas falls into black holes and how gas produces outflows that we observe, much stronger than what has usually been assumed,” says Tchekhovskoy. The results suggest scientists will have to re-evaluate their understanding of how black holes behave. www.vlba.nrao.edu
BULLETIN AUGUST 13
CUTTING Our experts examine the hottest new research
EDGE
þ The rings of fire – actually dust – in the Andromeda Galaxy appear to be the product of M32 plunging through its disc
Inner ring
M32 Outer ring
Spiralling shockwaves Could M32 be responsible for the future collision between the Andromeda Galaxy and our own?
NASA/JPL/P. BARMBY (CFA)
S
ometimes the fate of galaxies can be decided by nothing more than circumstance. That, at least, is one of the lessons from a new simulation of the complex dance being enacted by the Andromeda Galaxy, M31, and its neighbour M32. Both galaxies are familiar to backyard astronomers, and even a small telescope will show the contrast between the small compact shape of M32 and the nearly edge-on disc of M31. Both systems are somewhat unusual: infrared images show clearly a star-forming ring circling M31’s centre, while M32 is the prototype of a rare class of compact ellipticals with unexpectedly high central brightness but a mysterious lack of gas, which would shine in the infrared. Astronomers have been tempted for decades to blame all of these quirks on a mutual interaction between the two, and a paper by astronomers at Harvard presents the first really good simulation of such an encounter. It’s M31 that is the heavyweight here. M32 is hundreds of times less massive, yet the simulation shows that a single passage of the smaller galaxy through M31’s disc is enough to create spiralling shockwaves that spread out through the disc. When viewed from a nearly edge-on position, these structures appear as a ring. The mystery of M31’s rings is thus solved with a single encounter, which seems to have taken place about 800 million years ago. But M32’s
characteristics are not so easy to explain. The simulation does show that such a passage would reduce the mass of the smaller galaxy by a factor of 10, shrinking the galaxy’s size by 20-40 per cent, but a problem arises if you assume that M32 started life as a normal elliptical galaxy. If that were the case, then even such dramatic effects aren’t enough to explain how small it is today. If, on the other hand, it started off already compact, then we’d still need to explain how such compact galaxies form in the first place. One option is to propose multiple passages of M32 through the disc, but that seems extravagant when we can explain M31’s appearance by a single encounter. Understanding the system’s past is made harder by the motion of M31, which makes it difficult to determine such things as the distance to the galaxies. That motion may owe much to M32’s previous behaviour; in the simulation, even a single encounter with a galaxy of M32’s size is seen to significantly affect the speed of something as massive as M31. M31 is famously due to collide with the Milky Way in just a few billion years’ time, merging into what is likely to be a single elliptical system. If that collision is due to the nudge provided by M32, the fate of our own Galaxy might thus depend on the behaviour of this still mysterious system.
“The mystery of M31’s rings is solved with a single encounter”
CHRIS LINTOTT is an astrophysicist and co-presenter of The Sky at Night on BBC TV. He is also the director of the Zooniverse project.
CHRIS LINTOTT was reading… Signatures of the M31-M32 galactic collision by Marion Dierickx et al Read it online at http://arxiv.org/abs/1405.3990v1
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The planet’s Great Red Spot is dwindling with each decade 1995
2009
JUPITER’S GREAT RED Spot has shrunk to its smallest size on record. Measurements by the Hubble Space Telescope reveal it is now about 16,500km wide, less than half the size estimated in the 1800s. Over several decades, spacecraft have observed the storm gradually slimming down and recently it has become more circular than oval. Amy Simon from
2014
NASA’s Goddard Space Flight Center in Maryland says Hubble observations now suggest this is due to small eddies in Jupiter’s atmosphere feeding into the storm. “These may be responsible for the accelerated change by altering the internal dynamics and energy of the Great Red Spot,” she says. www.hubblesite.org
COSMIC CLUMPS CAST DARK SHADOWS NASA’S SPITZER SPACE Telescope has observed clumps of gas and dust so dark and dense that they throw the deepest shadows ever recorded. Bizarrely, they could clarify how very bright stars form. The clumps lie in a huge cloud 16,000 lightyears away. Their shadows allowed astronomers to measure the cloud’s mass, revealing that it’s likely to evolve into a star cluster containing very bright ‘O-type stars’, whose formation is poorly understood. “Spitzer has provided us with an important picture of massive star cluster formation caught in its earliest, embryonic stages,” says team member Jonathan Tan from the University of Florida. www.nasa.gov/spitzer
The dark cloud is obvious at the centre of this Spitzer shot; the inset shows it close up at one wavelength
Looking back Up until the 1920s, M31 was thought to be a nebula
skyatnightmagazine.com 2014
August 1972 On 16 August 1972, The Sky at Night broadcast discussed the Andromeda Galaxy, M31, which lies about 2.5 million lightyears away. The largest galaxy among our few dozen galactic neighbours, it contains roughly a trillion stars, at least twice the number in our own Milky Way. It is by far the most distant object visible to the naked eye. The Andromeda Galaxy has proven to be an excellent
‘laboratory’ that has fuelled astronomical progress. Until the 1920s, it wasn’t clear that some fuzzy patches of light in the night sky are separate galaxies, but American astronomer Edwin Hubble showed by 1925 that M31 is a huge galaxy in its own right. The Milky Way and M31 are rushing towards each other due to their mutual gravitational pull, and they’ll probably collide in about four billion years’ time.
NEWS IN
BRIEF SPA SELECTS NEW CHIEF STARGAZER Regular The Sky at Night presenter Lucie Green has been appointed as the new Chief Stargazer for the Society for Popular Astronomy. She now heads the Young Stargazers section of the society, which and aims to bring the excitement of astronomy to people under the age of 16. “For me astronomy is about working with other people and that is part of the thrill of it, having conversations and sharing your enthusiasm,” says Green, pictured below, who carries out solar research at University College London’s Space Science Laboratory. “That is what I’m looking forward to as Chief Stargazer.”
SUN–BOUND PROBE SURVIVES HEAT TESTS The protective shield for ESA’s Solar Orbiter has passed its high-temperature tests. Due for launch in 2017, the spacecraft will have an eccentric orbit that sometimes takes it closer to the Sun than Mercury, baking it to temperatures in excess of 500°C.
NASA/ESA AND A. SIMON (GODDARD SPACE FLIGHT CENTER), NASA/JPL-CALTECH/ UNIVERSITY OF ZURICH, THINKSTOCK, ESA-ANNEKE LE FLOC’H
Jupiter’s famous storm shrinks
15
CUTTING Our experts examine the hottest new research
EDGE
Why spin speed matters A planet’s rotation speed can drastically affect its climate – and possibly what defines a ‘habitable’ orbit
MARS EARTH MERCURY
ESA/NASA AND FRÉDÉRIC PONT (GENEVA UNIVERSITY OBSERVATORY)
T
consequently increase the temperature difference between the daylight and nighttime sides of the planet. Secondly, the Coriolis forces in the atmosphere would be weaker, and so lower the restriction on air convection patterns moving heat north and south from the sunny equator. In contrast, if Earth were to spin faster, the more powerful Coriolis forces would produce horizontal stripes of winds (just like the bands and zones of Jupiter) and clouds would only form in a narrow region in the tropics. This would decrease the whiteness of the planet, meaning more of the Sun’s heat would be absorbed and the climate would become hotter. The tropics are the most important areas for cloud cover, because these are the regions that receive the greatest flux of sunlight. For faster-spinning planets the tendency is for warming to cause a decrease in tropical cloud cover, which effectively darkens the albedo of a planet, meaning it gets even warmer and can eventually slide into a runaway greenhouse effect.
“If Earth were to spin faster, clouds would only form in a narrow region of the tropics”
VENUS
he concept of the habitable zone is a central issue in planetary science today, and a topic this column has touched back on several times. This Goldilocks’ Zone around a star is where the temperature is just right for liquid water and the possibility of life on a planet’s surface. How hot or cold a planet is is clearly dependent on how bright the star is, as well as the thickness and composition of the planet’s atmosphere. But what planetary scientists are starting to realise now is just how important other intrinsic properties of planets are. For example, a world’s rotation rate has strong effects on circulation patterns within its atmosphere and therefore the distribution of clouds, and thus in turn the overall climate. Clouds are the major contributor to Earth’s ‘whiteness’ (the planetary ‘albedo’) and so how much sunlight is reflected back out into space without heating the surface. Jun Yang and a team at the University of Chicago have used a sophisticated 3D model of atmospheric dynamics and cloud formation to investigate the effects of rotation speed on climate. Slowing down the spin of the Earth, say, would have two major effects. Firstly, the days would become longer and
Þ Venus could be potentially habitable today, calling current habitable zone models into question
LEWIS DARTNELL is an astrobiology research fellow at the University of Leicester. His latest book, The Knowledge, was published in April.
So Yang and his colleagues found that the width of the habitable zone around a star is strongly dependent on planetary rotation rate, as slow-spin worlds tend to have high albedos. Interestingly, their modelling predicts that Venus could still offer a habitable climate today. Despite orbiting almost 30 per cent closer to the Sun than us, if it had an Earthlike atmosphere rather than the thick blanketing one it has today, the temperature on the surface could have been much more hospitable. The implication is that for Venus to have undergone this runaway greenhouse process early in the Solar System’s history, it would have had to have a rotation period of less than a few weeks and slowed down since. The wider ramifications for exoplanet searches are that we may need to reassess what we define as habitable orbits around other stars. Yang argues that exoplanets previously dismissed as being too hot may still in fact offer habitable conditions, if they have slow rotations.
LEWIS DARTNELL was reading… Architectures of planetary systems and implications for their formation by Eric B Ford Read it online at http://arxiv.org/abs/1404.3157
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WHAT’S ON AUGUST 17
What’s on
Our pick of the best events from around the UK
Dalby Forest Starfest 2014 Dalby Forest, Yorkshire, 22-24 August 2014, 12pm This year’s Starfest will offer plenty of opportunities to explore the skies
PICK OF THE MONTH
Stars to Satellites Royal Observatory Greenwich, London, until 31 August 2014 Head to the Royal Observatory’s Astronomy Centre this month to find out how astronomical navigation gave birth to the modern ‘satnav’ in the Stars to Satellites exhibition. Admission is free and the event is suitable for all ages. www.rmg.co.uk.
Solar Observing Day Alnesbourne Priory, Ipswich, 24 August, 11am-4pm Join the Orwell Astronomical Society for a day of solar observing in the grounds of Alnesbourne Priory. Learn how to observe the Sun safely and talk to seasoned solar observers at this popular annual event. Contact
[email protected] for more information. Booking is not necessary. www.oasi.org.uk.
FORESTRY COMMISSION/TONY BARTHOLOMEW, THINKSTOCK X 2, NASA, ESA–C. CARREAU/ATG MEDIALAB
Peake Season Summer The 14th annual Dalby Forest Starfest star camp, organised by Scarborough & Ryedale Astronomical Society, will be taking place over the August bank holiday weekend. Over the three nights you can explore the dark skies over Dalby Forest, while the daytime activities will include lectures from guest speakers including BBC Sky at Night Magazine reviews editor Paul Money, trade stands for you to peruse
new astronomy equipment and even a rocket-building competition. The weekend will be rounded off on Sunday evening with an astronomy quiz. Places are limited and you do need to book as no admission will be granted to those who turn up ticketless on the day. Tickets cost £25 for adults and £10 for children. www.scarborough-ryedale-as.org.uk/ saras/starfest/starfest-2014
BEHIND THE SCENES
The National Space Centre, Leicester, until 31 August This summer the National Space Centre will be celebrating the UK’s first ESA astronaut by challenging the public to train like Major Tim Peake. As well as test activity challenges based on real astronaut training, there will be an ISS Science Zone and Mission Control centre to give you a glimpse of life in space. www.spacecentre.co.uk.
THE SKY AT NIGHT IN AUGUST Four, 10 August, 10pm (repeated
Four, 14 August, 7.30pm)*
ROSETTA’S RENDEZVOUS After a 10-year journey, this month the Rosetta spacecraft will catch up with comet 67P/ChuryumovGerasimenko and start one of the most exciting missions of this generation – to track and land on a comet. The Sky at Night travels to mission control to get an early look at the images coming back. Rosetta will eventually send a lander, Philae, to the surface of the comet
*Check www.radiotimes.com as times may vary
MORE LISTINGS ONLINE Visit our website at www. skyatnightmagazine.com/ whats-on for the full list of this month’s events from around the country. To ensure that your talks, observing evenings and star parties are included, please submit your event by filling in the submission form at the bottom of the page.
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A PASSION FOR SPACE AUGUST 19
A PASSION FOR
with Maggie Aderin-Pocock
The Sky at Night presenter reflects on our average star and its one USP: the fact that our planet has life
T
he long days Biomarkers in starlight and short could allow us to detect nights may not life on distant worlds be seen to be conducive to astronomical activities, but they can give us a wonderful opportunity to find out more about our local star, the Sun. On many scales the Sun can be seen as quite average: about average size, about average brightness. Even in the terms of categorisation it falls into the band in which the majority of stars sit, called the main sequence. So does it have a USP, a unique selling point? Well, to date the liquid water. And if we are looking for only unique feature we’ve confirmed about signs of life, a planet with liquid water on the Sun but have not yet found elsewhere is it seems like a very good place to start. But, the fact that one of its planets has life on it. if we find what we are looking for out there The search for signs of life beyond our (and we do have some very good candidates), Solar System is still in its infancy. To date how can we detect signs of life? just under 2,000 extrasolar planets (or exoplanets, to give them their slightly Marvel Comics name) have been discovered and Biological activity as we know it creates a that number is likely to greatly increase distinct chemical signature in a planet’s over the next few years due to further input atmosphere, so by analysing the spectrum from missions such as Kepler. Since it’s launch of that atmosphere, the chemical in 2009, the space scope has detected a composition and possible biomarker whopping 970 confirmed exoplanets and fingerprint could give us a strong a further 4,250 planet candidates. indication of whether life is out there. The holy grail would be to find EarthBut there lies the challenge: to detect sized planets that sit in their stars’ habitable exoplanets we use a range of techniques, zone, also known as the Goldilocks Zone and one of the more popular is to detect a since it is neither too hot nor too cold for drop in a star’s brightness as an exoplanet
THINKSTOCK
The secrets of starlight
transits across it. These light drops can be very small, but we have instruments sophisticated enough to detect them. What we do not have yet is instrumentation that has a high enough resolution to detect starlight passing though the thin band of atmosphere around an exoplanet, so it can be analysed for its chemical signature. This would seem like a show-stopper and delay our analysis until something like the European Extremely Large Telescope is completed in the 2020s. But astronomers are wily creatures and realised that if you analysed a star’s spectrum with and without a planet in transit, you could get a strong indication of the chemical content of the exoplanet’s atmosphere and search for those biomarkers indicating life. In the next decade or so we may be able to confirm that there is an indication of life out there on a few of our exoplanet neighbours. We could find that the Sun’s current USP no longer exists and that even in this respect it is quite average. But I think that the search for life may be a lot more challenging and that our star will prove to be rarer than we realised. S Maggie Aderin-Pocock is a space scientist and co-presenter of The Sky at Night skyatnightmagazine.com 2014
EXOPLANET EXCURSIONS AUGUST 21
JON CULSHAW’S
EX PLANET EXCURSIONS
MAIN ILLUSTRATION BY MARK GARLICK, PHOTO: EMMA SAMMS
Jon pops 40 years into the future to hear a METI transmission reach its destination I’VE DECIDED TO stay in the 55 Cancri system a little longer to visit a moon of 55 Cancri f, a gas giant contentedly perched at the heart of its star’s habitable zone. I’m also attempting a first in the Cruiser Globe – a spot of time travel. If I set our apparent exterior speed to slightly faster than that of light, some future directed time travel should be achievable, keeping our path to an orbital loop around 55 Cancri f at the distance the ISS orbits Earth. The reason for this trip in time is that in July 2003 the Evpatoria Planetary Radar sent a METI transmission, or Message to Extra-Terrestrial Intelligence, in the direction of 55 Cancri, hoping that there might be alien life to receive it. That signal should reach its destination in May 2055 and it’s to that point of time that I’m destined, to intercept the METI signal and play it through the Crusier Globe’s speakers. My daring time leap goes smoothly, despite my feeling that I’ve awoken from 1970s dental gas anaesthesia. With the Cruiser Globe’s planetary locators set to
‘moon grade’, it’s guided me to an equatorial plateau on a satellite of 55 Cancri f that’s roughly 1.5 times the size of Titan. This world is reassuringly Earthlike, with regions of dark green foliage interspersed with bizarre purple trees – if I can call them trees, being only around 1.5m in height – with a texture resembling broccoli. This all lies in long stretches beside flowing, liquid water. The habitable zone of 55 Cancri appears to be cradling flourishing swathes of vegetation. In this alien sky there’s a glorious view of 55 Cancri f, the gas giant weighing in around half the mass of Saturn and set off nicely with a thin ring system. The sight of this planet is arresting and imposing without utterly dominating the sky: a marvellous world calmly glowing like Earthshine cast on the Moon, and just a little lighter than the blue of the sky it occupies. Its appearance is almost like a hybrid of Saturn and Neptune. I don’t know whether to call it Satune or Nepturn. From this location and time, the METI signal should be just 3 AU away and
audible in about 25 minutes. I test the Cruiser Globe’s speakers with vintage sounds from my BBC Radiophonic Workshop CD. With a minute to go I pause the CD and precisely on cue, the METI message ‘Cosmic Call 2’ arrives at its destination. How fascinating to hear something the human race considered to be logically understandable by an alien form of intelligence – I hope I do count as a form of intelligence. The signal pulsates with ordered rhythms evocative of ‘Dreams of Leaving’, an early experimental track from the Human League’s Travelogue album. At the side of the water flows are a number of indentations tantalisingly resembling reptilian ‘footprints’ leading back into the foliage. If they are real they look like they could be from a small, bipedal creature about the size of a meerkat. Might they belong to an alien intelligence hearing the METI signal at this very moment? Jon Culshaw is a comedian, impressionist and guest on The Sky at Night
22
Interactive EMAILS • LETTERS • TWEETS • FACEBOOK This month’s Email us at
[email protected] top prize: four Philip’s books The ‘Message of the Month’ writer will receive four top titles courtesy of astronomy publisher Philip’s. Heather Couper and Nigel Henbest’s Stargazing 2014 is a month-by-month guide to the year and you’ll be able to find all the best sights with Patrick Moore’s The Night Sky. Stargazing with Binoculars by Robin Scagell and David Frydman contains equipment and observing guides, and you’ll be viewing planets, galaxies and more with Storm Dunlop’s Practical Astronomy.
MESSAGE OF THE MONTH How I made an observatory for my small garden Your readers may be interested in a further variant to the ideas you have printed in the last two issues on back garden observatories. Like many I have struggled with setting up in the dark and then having to put the equipment away at the end of a session. I’m always a little worried that in an early morning bleary eyed accident I would break a leg or the telescope. I have a very small garden close to listed buildings and I did not want to intrude into the neighbour’s view or spoil my own enjoyment of the garden. Initially I was very enthusiastic about a small 2 2m rolling roof design, until I realised it actually has a footprint of twice that size and would cover up too much of the garden. In the end I designed and built a ‘rolling sentry box’. I already had a very handsome 2.5 3m summer house and I asked the manufacturer to use the same design – except I wanted it to be 1 1m. I mounted it onto a base of one-inch marine plywood, out of which I cut a slot to go round the plinth. I mounted the sentry box on eight 2-inch diameter wheels which roll along a pair of 2.4m timber rails. The overall cost was just
over £1,000 including the plinth, and with a leaded glass door and side window it not only looks very attractive but is unobtrusive too. Since the beginning of April – when I finished the project – I have used it a dozen times without problem. David Roe, via email
An ingenious back garden observatory solution for a small garden, David. – Ed
Love at first click
Gove gripes
I have recently started to try robotic imaging with the Bradford Robotic Telescope and was impressed with the ease of use of the website. It can take a while for images to be taken but the anticipation is all part of it. This is a great way of getting into astro imaging without the expense of buying specialist equipment. This is my best result so far, of the Trifid Nebula, M20.
I am the director of the Tolcarn Research and Educational Observatory, which is based in St Stephen, near St Austell in Cornwall. I was truly dismayed to read an article in the Daily Mail (‘Bonfire of “soft” GCSEs’, 1 June 2014) with regards to the Education Secretary Michael Gove looking at scrapping GCSEs that are deemed to be ‘soft’. The astronomy GCSE is one of them. We at Tolcarn have been visiting schools throughout Cornwall and Devon promoting and encouraging astronomy to the younger generation and it is a subject that enthrals the students. The astronomy GCSE is not a mainstream subject taught in schools down here, but delivered as an additional subject by means of after school science clubs and similar. I have supported local schools with regards to the assignments for the GCSE astronomy coursework, making my research telescopes
Robert Farquhar, Cumbernauld
This month we’ve teamed up with the Bradford Robotic Telescope to offer a month’s free imaging for all readers. See page 20. – Ed < Robert’s robotic shot of the Trifid Nebula in Sagittarius skyatnightmagazine.com 2014
David’s tracked down a clever solution – his sentry box observatory has proved an able guard for his telescope
LETTERS AUGUST 23
The big debate Have your say at http://twitter.com/ skyatnightmag @skyatnightmag asked: Every month our columnist @jonculshaw ‘travels’ to another world in Exoplanet Excursions, but where in the comsos would you most like to go? @sjb_astro To a point where our Galaxy can be seen in its entirety – the view would be humbling yet awesome!
housed at the observatory available for the students to use. All school visits here and Tolcarn visits to schools will always be free of charge, it is important we give something back. If this course is dropped from the list of GCSEs, this, in my opinion will hamper students who want to follow careers in the space sciences. This amazing planet’s fossil fuels will eventually run out and we are going to be looking at other alternatives – ie, in space. I have written to my local MP making my concerns about this matter abundantly clear. It would be interesting to see what other BBC Sky at Night Magazine readers and subscribers think about this matter. Grant Mackintosh, Cornwall
I’m sure other readers will have an opinion on this matter too. Get involved with the discussion on Twitter via @skyatnightmag and Facebook on www.facebook.com/ SkyatNightMagazine. – Ed
Catching pings As you are aware there has been talk of a new meteor shower in May (Camelopardalid meteor shower, 24 May) as a result of Comet 209/P Linear. The attached demonstrates a graph of meteor detections by radio scatter in Lichfield, West Midlands. As you can see, it suggests we did indeed see such a shower. Dr Andrew Thornett, Lichfield
@chris_tsaftsaf Lave, the starting point for every Frontier gamer in the 80s!
What a fascinating observation, Andrew. Of course we were hampered by daylight on the day but it’s great to see evidence of increased activity around the time the peak was predicted. – Ed
@uk02591 Kasterborous :)
BBC Sky at Night Magazine is published by Immediate Media Company Bristol Limited under licence from BBC Worldwide, who help fund new BBC programmes. EDITORIAL Editor Chris Bramley Art Editor Steve Marsh Production Editor Kev Lochun Online Editor Kieron Allen Staff Writer Elizabeth Pearson Reviews Editor Paul Money CONTRIBUTORS Paul Abel, Ade Ashford, Maggie Aderin-Pocock, Rob Banino, Sean Blair, Paul F Cockburn, Jon Culshaw, Adam Crute, Lewis Dartnell, Glenn Dawes, Vincent S Foster, Mark Garlick, Will Gater, Nicky Guttridge, Olivia Johnson, Brian Jones, Carol Lakomiak, Pete Lawrence, Chris Lintott, Hazel Muir, Steve Richards, Steve Sayers, Paul Sutherland, Stephen Tonkin ADVERTISING SALES Advertising Director Caroline Herbert Advertising Managers Steve Grigg (0117 314 8365), Tony Robinson (0117 314 8811) Inserts Laurence Robertson (00 353 87 690 2208) PRODUCTION Production Director Sarah Powell Production Manager Derrick Andrews Ad Services Manager Paul Thornton Ad Co-ordinator Emily Thorne Ad Designers Cee Pike, Andrew Hobson Reprographics Tony Hunt, Chris Sutch LICENSING Head of Licensing and Syndication Joanna Marshall MARKETING Head of Circulation Rob Brock Head of Marketing Jacky Perales-Morris Marketing Executive Chris Day Head of Press and PR Carolyn Wray (0117 314 8812) PUBLISHING Publisher Jemima Ransome Managing Director Andy Marshall MANAGEMENT Chairman Stephen Alexander Deputy Chairman Peter Phippen CEO Tom Bureau
@Wingfoil I would love to travel to the edge of our known Universe and look into the void, then spin and look back at our Universe.
BBC WORLDWIDE, UK PUBLISHING Director of UK Publishing Nicholas Brett Head of UK Publishing Chris Kerwin Head of Editorial, UK Publishing Jenny Potter UK Publishing Coordinator Eva Abramik
[email protected] www.bbcworldwide.com/uk--anz/ukpublishing.aspx EDITORIAL ADVISORY BOARD Deborah Cohen, Andrew Cohen, Michael Ewing, Julian Hector, John Lynch, Jonathan Renouf
@SkwerrWheels I’d travel to the Shapley Supercluster.
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Þ The Lichfield Radio Observatory’s instruments recorded
an increased number of meteors on 23-25 May
......................................................................................... OOPS! • In our June issue we wrongly stated that supermassive black holes have masses of 105 to 1,010 the mass of the Sun. The correct calculation should have read 105 to 1010 the mass of our Sun. • In last month’s issue we incorrectly attributed the Message of the Month to Michael Crouch. It was in fact Bob Ford who wrote the winning letter and built the impressive roll-off roof observatory it mentioned.
© Immediate Media Company Bristol Limited 2014 ISSN 1745-9869
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26
Hotshots This month’s pick of your very best astrophotos
PHOTO OF THE MONTH
S The Sun PAOLO PORCELLANA, ASTI, ITALY, 30 MARCH 2014 Paolo says: “The day I took this image the sky was a beautiful shade of blue with high transparency and average seeing. I decided to take the opportunity to make a small mosaic of the main feature on the disc. The detail and contrast in hydrogen-alpha was great at a focal length of 3m.” Equipment: Point Grey Chameleon monochrome CCD camera, Home-made 6-inch truss refractor. BBC Sky at Night Magazine says: “With this outstanding close-up of the Sun, filaments seem to jump out of the page, appearing almost 3D set against the texture of the photosphere. The image
skyatnightmagazine.com 2014
has a great sense of fluidity to it that captures the violent activity and ever-changing face of our star.”
About Paolo: “I’ve been an amateur astronomer ever since I was 15 years old and still dedicate all my free time to astronomy. I’m particularly fascinated by astrophotography and I try to experiment with different image techniques to achieve the best results.“
S Noctilucent clouds STEVE LANSDELL, NORWICH, 24 JUNE 2014 Steve says: “On the night that I took this photo, I glanced out of the window before bed and I could see the basket-weave pattern above the roof tops. I grabbed my camera and my daughter Storm, and we ran to the end of the road to shoot this amazing display.” Equipment: Canon EOS 5D MkII DSLR camera.
HOTSHOTS AUGUST 27
W The PacMan Nebula PREDRAG KNEZEVIC CROATIA 1 SEPTEMBER 2013 Predrag says: “As the name suggests, this nebula bears some resemblance to the videogame character Pac-Man if it’s captured in lower resolution. When viewed in finer detail that resemblance is gone, but a very rich and beautiful stellar nursery is revealed.” Equipment: Atik 383L+ monochrome CCD camera, Teleskop-Service 6-inch triplet apo refractor, Celestron CGEM mount.
T The Moon JOHN CHUMACK, OHIO, 10 MAY 2014 John says: “The waxing gibbous Moon looked close to Mars on the night this shot was taken. If you went out and took a quick look you would have seen a bright red ‘star’ to the left.” Equipment: Canon EOS Rebel XSi DSLR camera, 10-inch Schmidt-Cassegrain.
S The Milky Way STEVE BARRETT, TENERIFE, 5 JUNE 2013 Steve says: “I took this shot under dark skies near the top of Mount Teide in Tenerife. This image of the Milky Way running through Sagittarius and Scorpius reveals many Messier objects. Near the centre are the Lagoon and Trifid Nebulae; towards the top left are the Eagle and Swan Nebulae.” Equipment: Nikon D7100 DSLR camera, 85mm f/1.8 lens, iOptron SkyTracker mount.
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28 HOTSHOTS AUGUST
T The Sun IVAR KOOREN, THE NETHERLANDS, 18 MAY 2014 Ivar says: “This image of the Sun was taken in four sittings, generating 4,800 frames that were eventually stacked.” Equipment: ASI120MM CCD camera, SolarMax 60S telescope, NEQ6 mount.
S The Squid Nebula PAUL JENKINS, COUNTY DURHAM, 1 AND 4 APRIL 2014 Paul says: “I thought I’d have a go at imaging this object using a 5nm OIII filter. After spending four hours on it, my images revealed nothing. I then borrowed a 3nm OIII filter and imaged for eight hours. The individual files still showed nothing, but I then stacked the images and wow… suddenly I could see it.” Equipment: QSI 583 CCD camera, Tele Vue-NP101is telescope.
W The Wall in NGC 7000 MARK GRIFFITH SWINDON 19 APRIL 2014 Mark says: “Having a go at this object in the North America Nebula, NGC 7000, I used the Hubble palette to revel as much detail as possible. I didn’t quite have the field of view for the whole Wall, but the middle bit looked to be the most interesting.” Equipment: Atik 383L+ CCD camera, Celestron C11-SGT telescope, SkyWatcher NEQ6 Pro mount.
ENTER TO WIN A PRIZE! WORTH
£99
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We’ve teamed up with the Widescreen Centre to offer the winner of next month’s best Hotshots image a fantastic prize. The winner will receive an Orion StarShoot Solar System Colour Imager IV camera, designed for capturing sharp shots of the Moon and planets. www.widescreen-centre.co.uk • 020 7935 2580
Email your pictures to us at
[email protected] or enter online.
E ! V R SI FE U F CL R O EX DE A
RE
CAPTURE TOP AUGUST OBJECTS FOR FREE WITH A
ROBOTIC TELESCOPE BBC Sky at Night Magazine has teamed up with the University of Bradford to bring you one month of access to its robotic telescope, FREE with this magazine This exclusive offer gives you free use of the Bradford Robotic Telescope, located in the best observing site in Europe, 8,000ft above sea level on the island of Tenerife. From this prime location, this fully autonomous observatory will take pictures of the night sky at your request. All you need to do is follow the instructions below to register on the Bradford Robotic Telescope’s website and the facility’s state-of-the-art imaging systems will be available to you FREE for a month. Once registered, just choose a target from the six listed below and the images will be taken for you automatically while you’re sleeping. Log on a few days later and you’ll find your images waiting for you. You’ll then be able to use the telescope’s online image processing tools to get the most from your pictures – all absolutely FREE!
HOW TO GET YOUR MONTH’S FREE ACCESS
1. Go to telescope.org/SaN 2. Enter the access code ANDROMEDA 3. Try out imaging the six objects below for one month SEE BELOW FOR DETAILS OF THE TERMS AND CONDITIONS FOR THIS OFFER
IMAGE THESE 6 CELESTIAL WONDERS THE DUMBBELL NEBULA This is a bright planetary nebula: the remnants of a dying star and a peek into the future of our own Sun. The red areas are ionised hydrogen and nitrogen, with oxygen showing up in green.
THE HERCULES GLOBULAR CLUSTER Global clusters are among the oldest structures in the Galaxy, around 11 billion years old. This one is thought to contain around 300,000 stars. Might there also be a black hole at its centre? THE MOON A favourite of astronomers for centuries, take a simple image of our nearest neighbour up close. Take detailed images of craters and watch as the Moon changes over the lunar month.
THE MILKY WAY The Bradford Robotic Telescope is equipped with two wide-field cameras: the widest is able to capture our own Galaxy in all its glory. Glowing areas of star formation and dark obscuring dust show up clearly.
COMET C/2012 K1 PANSTARRS Having peaked earlier in the year, this comet is still a perfect example of how beautiful these balls of rock and ice can be. The tail is still very bright on this everchanging comet. THE ANDROMEDA GALAXY The closest large galaxy to our own, Andromeda is on a collision course with the Milky Way. As a result it appears very large in the sky and makes a great target for the mid-field camera.
Terms and conditions: Promoter is The University of Bradford, Robotic Telescope, School of Engineering & Informatics, University of Bradford, Bradford, BD7 1DP. Entrants must not be employees of the Promoter or Immediate Media Company. Entrants will receive an email confirming registration details immediately after registration. Entrants will have access only to the 6 objects described above. Entrants may access the offer for 1 calendar month from date of registration. Access code active until 11.59pm, 1 September 2014. On 1 January 2015 all Entrant accounts become regular unpaid accounts, which can be reactivated on payment of the standard fee of £3/month. The Promoter’s privacy policy applies, see http://www.telescope.org/privacy-terms-conditions.php
Theglowing
ghosts NASA/ESA/C. ROBERT O’DELL (VANDERBILT UNIVERSITY) AND DAVID THOMPSON (LBTO)
Our night skies are adorned with the remains of long-dead stars – planetary nebulae. Will Gater looks at the science behind them
O
ne of my earliest childhood memories of stargazing is of the night I set out to track down the Ring Nebula in Lyra. It was a summer evening and I’d barely had my first telescope for six months. I remember lugging the heavy pier and its three weighty, metal feet out onto my parents’ driveway. And I remember how carefully – almost reverentially – I would lower the scope into the felt-lined tube rings, checking the screws repeatedly to make sure it wouldn’t slip. Eventually, after much turning of knobs and squinting through the finderscope, the nebula moved into view and there in the eyepiece was the exquisite grey ring set against a scattering of stars.
The Ring Nebula, M57, belongs to a class of objects that astronomers call planetary nebulae. It was their likeness to planetary discs when studied with early telescopes that led to these nebulae being given this somewhat confusing moniker, but it’s stuck ever since. Today we know that these intricate sculptures of gas and dust are in fact what’s left when a Sunlike star dies – a beautiful, glowing ghost of the star that once shone in its place. Robert O’Dell’s interest in these enigmatic objects developed in graduate school where he got to work alongside experts in the field. “I’ve worked in other areas too,” he says today. “But I always seem to return to planetary nebulae.” Now a professor at Vanderbilt
University in Tennessee, O’Dell – along with colleagues in the US and Mexico – recently used the Hubble Space Telescope to study the Ring Nebula in unprecedented detail. But Hubble’s spectacular pictures only show the end point of the planetary nebulae-forming process. The real secret of how the Ring Nebula was made lies with what happens when a Sun-like star approaches the end of its life.
Death and birth In their old age, stars with a similar mass to the Sun puff up in size, developing into red giants. Gradually, however, the fuel reserves within these bloated behemoths begins to wane and they evolve from >
The astounding Ring Nebula is the remnant of a collapsed Sun-like star
The disc of material around the Eskimo Nebula resembles a face in a fur hood
Sometimes puffed-off gas funnels towards the poles, creating bipolar nebulae like Hubble 12 here
ESO X 2, NASA/ESA,NASA/ANDREW FRUCHTER AND THE ERO TEAM [SYLVIA BAGGETT (STSCI) RICHARD HOOK (ST-ECF) ZOLTAN LEVAY (STSCI)], X 2, ESA/NASA & R. SAHAI, ALMA (ESO/NAOJ/NRAO)/M. MAERCKER ET AL
Ultraviolet light exciting oxygen atoms gives the Helix Nebula its blue-green hues
> being red giants into objects that astronomers refer to as ‘asymptotic giant branch’ stars, or AGB stars for short. “These are stars of a few times the mass of our Sun, but not many times the mass of our Sun,” explains O’Dell. “They’ve depleted their nuclear fuel reserves, and have insufficient mass and gravity as they collapse to heat up enough to burn the remaining nuclear components. They have no choice at that point except to collapse.” The onset of this collapse marks the beginning of the end for the star, but also the start of the birth of a planetary nebula. “At the beginning, the outer part of the star is essentially sloughed off in a slow process called a stellar wind, which is much more intense than the [solar] wind of our Sun,” says O’Dell. Later on, as more of the dying star’s atmosphere is shed, another process comes into play too. “As the collapse gains momentum a significant mass loss occurs,” explains O’Dell. “The star begins to heat up so much that it heats up the gas that it has sloughed off and that gives it an extra kick.” This heating has the effect of driving material out into space, creating enormous shells of gas and dust around the doomed star.
uncovered an intricate spiral pattern in the ejecta from the star R Sculptoris (see ‘A star’s final gasps’, right). Planetary nebulae progenitors don’t stay veiled forever though; amid the clouds of gas and dust that they’ve thrown out, an extraordinary object emerges from its fiery chrysalis. “When the matter has been expelled, the very hot core [of the star] will be exposed,” explains Henri Boffin, an astronomer at the European Southern taken by the Hubble Space Telescope Observatory. “A very fast but tenuous (below right) to appreciate the wind is ejected by this core remarkable cloaking nature of with velocities of several these dust clouds; it shows hundreds of kilometres a series of shells, and a per second. This thick blanket of dust, collides with the swathing the dying previously ejected star – all of which is material and pushes dimly illuminated it into a narrow by the light from shell of gas.” nearby stars. Astrophysicists Telescopes observing call this newly at longer wavelengths emerged stellar core than visible light can, a ‘white dwarf’. however, peer deeper into To reach the stage where the dusty environs of AGB a white dwarf is formed, stars. Recently ALMA, the Spiralled shells of dust an AGB star will eject Atacama Large Millimeter/ wind around the star an enormous amount of Submillimeter Array, LL Pegasi “Before it gets to this stage though, the star making the planetary nebula can often be obscured at visible wavelengths by the large amounts of dust it has already produced,” says O’Dell. One need only look at the image of the star LL Pegasi
“Amid the clouds of gas and dust, an extraordinary object emerges from its fiery chrysalis”
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With its streaks and swirls, it’s little wonder that IC 418 is known as the Spirograph Nebula
Abell 33 in Hydra is unusually symmetrical, forming a near-perfect circle The Little Ghost Nebula; our Sun may create a similar one, but not for five billion years
material. For some stars that can mean that most of their mass is lost as they die. But, as O’Dell points out, there’s a mystery that astrophysicists still have to figure out about this crucial phase of planetary nebulae creation. It concerns the mass of the white dwarf that’s produced. “They all have a mass of about 60 per cent of the mass of our Sun,” says O’Dell. “And yet the stars that create them have a variety of masses, typically several times that of our Sun.” It’s as if the stars can tell how much gas and dust they need to expel in order to eventually reach that allimportant figure of around 60 per cent. “It means that if you start with a star of three solar masses, it’s expelled 80 per cent – the majority of its mass. Whereas a star that starts out with 1.5 solar masses has only thrown off a smaller proportion of its mass,” adds O’Dell.
Hot and shiny While we don’t know how they all get to be roughly the same mass, we do know that it’s the white dwarfs at the centres of planetary nebulae that are responsible for making these striking objects shine. O’Dell likens the process that causes the ejected gas to glow to an effect you may have seen the last time you were in a nightclub or disco, that of ultraviolet lights on white clothes. “The ultraviolet photons >
A STAR’S FINAL GASPS The spiral around R Sculptoris hints at the presence of a hidden companion star
In 2012 astronomers from the European Southern Observatory announced that they had used the Atacama Large Millimeter/ Submillimeter Array (ALMA) to reveal an intriguing pattern in the ejecta around the asymptotic giant branch star R Sculptoris. ALMA consists of an array of 12m and 7m dishes situated in Chile’s Atacama Desert. From here it peers out at the light that comes from the Universe with wavelengths between those of infrared radiation and longer radio waves. By observing R Sculptoris at these wavelengths the ALMA astronomers were able to see a shell of gas
enveloping the star and uncover a never-before-seen spiral structure within it. The shell was ejected from the star in what astronomers call a ‘thermal pulse’, where gas and dust is blasted from the ageing giant as it experiences a relatively fleeting period of enhanced nuclear fusion. Analysis of the spiral of material around R Sculptoris indicates that it experienced one of these energetic thermal pulses some 1,800 years ago. The spiral is also compelling evidence that the star is part of a binary star system say the ALMA researchers (see ‘A deathly dance’, page 35).
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A DEATHLY DANCE Fleming 1’s twisting streamers are a result of it being part of a binary star system
Look at any selection of planetary nebula images and you’ll see everything from billowing, coloured clouds and brightly glowing shells to delicate bubbles and intricate swirls. “Such diversity is a pleasure for the eyes but also for the mind, as we need to understand them,” says Henri Boffin, an astronomer at the European Southern Observatory. “As a star is spherical, the mass loss by a single star should be symmetrical. So a typical planetary nebula will be a bubble of bright gas.” The problem is planetary nebulae
aren’t all bubbles. “Astronomers have found that about 80 per cent of planetary nebulae aren’t round at all, but come in a wide variety of shapes. They display axial and point symmetries, sometimes with jet-like structures,” says Boffin. The key to understanding how these varied structures form appears to be the way in which material is shed from the star at the end of its life. “To explain such shapes, we need to assume that the matter lost by the giant star was not spherical in shape, but must have been preferentially
ejected in a dense torus,” argues Boffin. “The question is, what causes that torus?” Many astronomers believe the culprits are binary star systems. “The star that lost its mass was part of a stellar couple and it’s the companion that focused the matter into the orbital plane,” Boffin says. “This natural explanation has been confirmed in several cases.” In fact, a group led by Boffin recently used the Very Large Telescope to uncover the binary star system responsible for creating the twisting streamers in the planetary nebula Fleming 1.
IC 4593, aka the WhiteEyed Pea Nebula, possesses a giant halo three times the size of the inner nebula
The ‘wings’ of the Butterfly Nebula are hotter than 36,000°C and travel at more than 965,000km/h
IC 5148 is one of the fastest expanding planetary nebulae known, growing at a rate of over 50km/s
> [from] the light strike a white surface, let’s say a starched shirt, and it glows with lower energy photons – it glows with basically white light,” he says. “White light has a longer wavelength [than ultraviolet] that the human eye can see better than those ultraviolet photons given out by the lamp.” Freshly made white dwarfs are blisteringly hot – usually around 100,000˚C – meaning they blaze brightly at ultraviolet wavelengths. It’s this energetic ultraviolet radiation that streams out from the white dwarf into the surrounding planetary nebula, making it glow. “These very high energy photons are absorbed by the gas and when that happens they throw off electrons in a process we call ionisation. You remove an electron from an atom and it’s ionised, it leaves an ion,” explains O’Dell. “These free electrons eventually find another ion and recombine to form a neutral atom and as they do that they give off the light that we see.”
nebulae appear rather red,” says O’Dell. “That’s because the gas in them isn’t very highly excited. Whereas the older ones, like the Ring Nebula, have some red but a lot of green and blue-green, and that’s because that’s the signature of oxygen gas
nebula. “That halo is about three times the size of the visually bright nebula,” explains O’Dell. We astronomers won’t always have this beautiful, glowing structure to gaze at in our night skies though. As the white dwarf at the heart of the nebula cools down, the surrounding gas will dissipate and fade too. It’s a fate that awaits all planetary nebulae. “The period of visibility is measured in a few tens of thousands of years,” says O’Dell. With that in mind, perhaps I ought to arrange a reunion with my old friend M57 this summer, before it’s gone for good. In fact, I know just the scope for the job. S
“Ultraviolet radiation streams out from the white dwarf into the planetary nebula, making it glow”
Colour clues The glorious colours of planetary nebulae are often an indication of the conditions found within them. “Very young planetary
that has been very highly excited because now the [white dwarf] is very hot.” In studying the Ring Nebula with Hubble and ground-based instruments, O’Dell and his colleagues have been able to develop a detailed understanding of the three-dimensional shape of an object that looks distinctly flat through amateur telescopes. “What we found was that in this case we’re looking at a planetary nebula that’s pretty old. We’re viewing it from almost along its polar axis,” says O’Dell. “It has a thick, equatorial belt of dense gas and the inside of that has been photo ionised.” The main ring is embedded within a series of haloes including a faint outer one that can be seen in very deep, long-exposure images of the
ABOUT THE WRITER Will Gater is a journalist and the author of several astronomy books, he also appears on TV and radio to talk about space. Find him on Twitter: @willgater
Turn the page for a list of the 12 best planetary nebulae to observe this month
MyCn18’s hourglass shape may be the result of a fast stellar wind amid a more slowly expanding gas cloud
The Cat’s Eye Nebula’s intricate structures include knots of gas, high-speed jets and at least 11 concentric rings Minkowski 2-9 in Ophiuhcus is also known as the Twin Jet Nebula – an apt name as its gas ‘exhausts’ are bellowing out at 320km/s
ESO/H. BOFFIN, NASA AND THE HUBBLE HERITAGE TEAM (STSCI/AURA), NASA/ESA AND THE HUBBLE SM4 ERO TEAM, ESO, NASA/ESA/HEIC AND THE HUBBLE HERITAGE TEAM (STSCI/AURA), RAGHVENDRA SAHAI AND JOHN TRAUGER (JPL) THE WFPC2 SCIENCE TEAM AND NASA, BRUCE BALICK (UNIVERSITY OF WASHINGTON) VINCENT ICKE (LEIDEN UNIVERSITY THE NETHERLANDS) GARRELT MELLEMA (STOCKHOLM UNIVERSITY AND NASA
PLANETARY NEBULAE AUGUST 35
36 PLANETARY NEBULAE AUGUST
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OF THIS MONTH’S BEST PLANETARY NEBULAE with Vincent S Foster
W DUMBBELL NEBULA (M27) VULPECULA Mag.: +7.1 Size: 8x5.7 arcminutes RA: 20h 00m 12s Dec.: 22º 45’ 29” Filter: OIII & UHC Description: A 4-inch scope at 100x magnification shows a large, bright disc pinched in the middle on its east and west sides.
CAT’S EYE NEBULA (NGC 6543) DRACO Mag.: +8.1 Size: 0.4x0.3 arcminutes RA: 17h 58m 33s, Dec.: 66º 38’ 05” Filter: OIII & UHC Description: An 8-inch scope at 100x magnification reveals a bright, blue-green disc elongated northeast to southwest.
NGC 6781 AQUILA X Mag.: +11.6 Size: 1.9x1.8 arcminutes RA: 19h 19m 00s Dec.: 06º 34’ 07” Filter: OIII Description: An 8-inch scope at 125x magnification shows a bright, circular disc with a trace ring and a dark centre. NGC 6891 DELPHINUS Mag.: +10.4 Size: 0.2 arcminutes RA: 20h 15m 49s Dec.: 12º 44’ 52” Filter: None Description: Direct vision in an 8-inch scope at 200x magnification reveals a bright, round disc with a mag. +12.4 central star.
LITTLE GHOST NEBULA (NGC 6369) OPHIUCHUS Mag.: +11.5 Size: 30 arcseconds RA: 17h 30m 12s Dec.: –23º 46’ 01” Filter: None Description: A 14-inch scope at 200x magnification reveals a filled shell with a dark centre. The central star is not visible.
THINKSTOCK X 2, PETE LAWRENCE X 2, NOAO/AURA/NSF
BLUE FLASH NEBULA (NGC 6905) DELPHINUS X Mag.: +10.9 Size: 0.8x0.6 arcminutes RA: 20h 23m 00s Dec.: 20º 09’ 10” Filter: OIII Description: A 10-inch scope at 200x magnification reveals a bright, bluish, unevenly illuminated disc slightly elongated north-south. ESKIMO NEBULA (NGC 2392) GEMINI Mag.: +9.2 Size: 0.8x0.7 arcminutes RA: 07h 30m 00s Dec.: 20º 52’ 40” Filter: None Description: A 4-inch scope at 150x magnification shows a small, bright, bluish disc surrounding a conspicuous yellow central star.
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BOX NEBULA (NGC 6309) OPHIUCHUS Mag.: +11.5 Size: 0.3x0.2 arcminutes RA: 17h 14m 51s Dec.: –12º 55’ 24” Filter: OIII Description: An 8-inch scope at 200x magnification shows a rectangular shape. The central star is visible and the disc greenish.
NGC 7009 CYGNUS X Mag.: +10.9 Size: 0.5x0.2 arcminutes RA: 21s 06m 48s Dec.: 47º 54’ 39” Filter: OIII Description: An 8-inch scope at 250x magnification shows bright, bluish-green bipolar nebula extending northwest to southeast.
MEDUSA NEBULA (Sh2-274) GEMINI Mag.: +14.0 Size: 12.4x8.5 arcminutes RA: 07h 29m 50s Dec.: 13º 12’ 34” Filter: OIII Description: A 14-inch scope at 75x magnification shows a faint, rather large and irregular nebula. The northeast end is brighter.
RING NEBULA (M57) LYRA X Mag.: +8.8 Size: 1.4x1.1 arcminutes RA: 18h 54m 07s Dec.: 33º 02’ 54” Filter: None Description: An 8-inch scope at 100x magnification shows a greenish hue with red at the outer edges. It has a well-defined centre, but no hint of a central star.
BLUE RACQUETBALL (NGC 6572) OPHIUCHUS Mag.: +8.0 Size: 0.3x0.2 arcminutes RA: 18h 12m 48s Dec.: 06º 51’ 48” Filter: None Description: A 6-inch scope at 100x magnification shows a star-like planetary, but its intense blue-green colour gives it away.
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ABOUT THE WRITER
THINKSTOCK X 2
Dr Elizabeth Pearson is BBC Sky at Night Magazine’s staff writer. She gained her PhD in extragalactic astronomy at Cardiff University.
THANK YOU TO THE FOUR COURSES ON THESE PAGES WHO EACH SUPPLIED IMAGES, DONNA BOOMGARDEN
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f you’ve ever wanted to learn about the Universe from a Nobel Prize-winning scientist, now’s your chance. World-renowned experts are lecturing on almost every subject to thousands of people online, and you can be one of them. All you need is a web connection. Massive open online classes, or MOOCs, are classes uploaded to the internet by some of the best universities around the globe and are completely free. Whatever your interest, there’ll be a MOOC to match, and astronomy is no exception. There are dozens of courses and each one runs over several months. The classes are taught through a series of videos that mirror traditional university classes, but are broken up into short segments. “What works best in a lecture theatre doesn’t necessarily work best when you’re sat at home in front of your computer,” says Catherine Heymans, a lecturer from the University of Edinburgh who runs the MOOC ‘AstroTech’ on Coursera with Andy Lawrence. “We found that after about seven minutes our minds were wondering. Most people’s concentration span is about 10 minutes, so we’ve gone for very short videos.”
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MOOC LISTING SITES COURSERA www.coursera.org EDX www.edx.org OPEN2STUDY www.open2study.com UDEMY www.udemy.com UDACITY www.udacity.com FUTURE LEARN www.futurelearn.com
As well as being easier to understand, the videos can be downloaded, so you’re free to learn the secrets of the cosmos while you commute to work, exercise at the gym or whenever else suits you. There are also tests, quizzes and assignments so you can evaluate how well you’ve understood what you’ve learned, along with busy forums where students can discuss the course. MOOCs are designed to fit in around a busy schedule. While the course is running, students are free to choose what lectures they watch, whether to take the quizzes and how much time they want to invest. Some only watch a few hours of the videos while others spend over 20 hours a week working through problems and talking with other students. Finding a course is easy, just search through the many MOOC providers to find the right one for you. Different lecturers will pitch their lectures at different audiences. While some will be for beginners, others will be for more advanced students so it’s worth spending some time looking through the available material to make sure it’s at a level you’re comfortable with. The courses are pitched to a university standard, so a basic knowledge of school physics and maths >
PLOT YOUR COURSE There are dozen of astronomy MOOCs available – this is just a brief selection
GREATEST UNSOLVED MYSTERIES OF THE UNIVERSE (EDX) Nobel Prize-winner Brian Schmidt and Paul Francis of the Australian National University take their students on a walk through the mysteries of the Universe, and show that we still have a lot left to discover. One of the main features of this course is the mysterious simulated Universe, created by Francis, which he then invites students to
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investigate. He replicates the kinds of data that real researchers produce, and invites his students to decide what ‘observations’ they should do next. “I supply the students with a few clues to begin with,” says Francis, “and they then have to come up with ideas, and propose observations to me. I then generate the data
they requested and post it the following week. It’s intended to be as close as possible to what a real researcher does.” The course is part of an XSeries, where students can take a series of courses to eventually gain an EdX diploma. Though the course is currently halfway through, it will be available again next spring.
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THE SCIENCE OF THE SOLAR SYSTEM (COURSERA) Mike Brown, a professor of planetary astronomy at Caltech and discoverer of Sedna, takes his students on a journey through our Solar System. The videos were created for his Caltech course, so a higher level of prior knowledge is needed for this than other MOOCs. “It’s not an intro for people who don’t know about science” says Brown. “But I encourage people to stick around and if they get to a section where they just don’t get what’s going on, they can click through to the next video. They’re welcome to audit it and not take the exams, or to watch the 10 lectures they like the most. “We also post the real problem sets from the class for Caltech students. We don’t grade them. People just do them for fun and we post the solutions. If they want to they can get the full rigorous version of what we were doing, and see whether they’re doing it right and if they don’t want to, they don’t have to.”
ASTRONOMY STATE OF THE ART (UDEMY) Chris Impey, a distinguished professor at the University of Arizona brings you up to date with the latest developments in astronomy by covering the science of recent discoveries and the technology that led to them. “The course is aimed at interested, self-motivated adults,” says Impey. “It emphasises cutting-edge topics where progress has been rapid: big telescopes, adaptive optics, Mars exploration, exoplanets, compact stellar remnants, surveys of galaxies, dark matter and dark energy, and studies of the early Universe.” Besides the videos, Impey also uploads additional information for students to look through as and when they wish. Every week features a podcast with interviews with some of the leading researchers in all aspects of astronomy, from planetary science to cosmology. Impey plans on running the course again next year, updating the videos to cover the latest advancements in astronomy.
ASTRONOMY: DISCOVERING THE UNIVERSE (OPEN2STUDY) John Morgan from Curtin University in Perth offers a general course on astronomy. Covering the subject’s history and how we have come to our current knowledge of the Universe, the course is designed as a beginners’ guide, so requires little prior knowledge. “I worked hard to give the course as wide an appeal as possible,” says Morgan. “Many lovers of astronomy are not scientists and would be put off by lots of maths. But others find some popular science rather patronising. Trying to strike the right balance was challenging, but I think there’s something here for everyone.” The course runs on the Open2Study platform. Unlike the other MOOC providers, Open2Study has a dedicated production team, so the videos are well shot and look professional. Courses are repeated every two months so you’ll never miss out, but the forum is overseen by a panel of non-specialist assistants rather than the lecturer.
CASE STUDY Donna Boomgarden, Chicago, US Studying: The Science of the Solar System One of the reasons I took this course is that I love learning about planets, stars, black holes and comets. If I were better at maths I’d have gone into astronomy as a profession. Alas, maths and I are mortal enemies! I also took this class to get updated on the latest information. My last astronomy class was when I was in college in 1984 and a lot has changed since then. Prof Mike Brown is a remarkable instructor and I’m honoured to
have him as my teacher for this class. I’m learning so much. I spend about six to eight hours a week on this class, watching the videos and taking notes. I’ve recommended MOOCs to all my friends and many of them are taking one of the courses now. They had no idea such a learning opportunity existed and were glad to discover them as returning to college for some ‘fun’ courses was financially unfeasible for them.
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> is needed. If it’s been a few years since you’ve sat in a classroom and your science is a little rusty, there’s no need to worry. Several of the sites offer refresher courses in the basics that you can start with before moving on to something more challenging. “If you have 20,000 students, you’re going to have all ranges of ability,” says Heymans, “What’s great about MOOCs is that you can have courses for a whole range of abilities. People can take the one that’s best for them and then build up.”
CATHERINE HEYMANS, UNIVERSITY OF EDINBURGH, THINKSTOCK X 2, SYLVIAN CHAMBON
Watch and learn Many courses are based on classes taught in reallife universities, and the MOOCs run in real time alongside them. The videos and assignments are posted online each week, but students are free to join and watch the videos at any time before the course ends. There are advantages to taking the course as it’s published, however. The discussion forums are one of the ways that students can feel as though they’re actually part of a classroom rather than working alone. The lectures and assignments draw people to the boards to discuss what they learned that week. “Every minute something new is posted,” says Heymans. “There are so many interesting conversations going on as the students help each other. We have a team of teaching assistants that go online and check things are okay but generally it’s the students who answer each others’ questions.” It’s this interaction between students and teachers that sets MOOCs apart from other online
CONTINUED EDUCATION CENTRES OXFORD UNIVERSITY www.conted.ox.ac.uk CARDIFF UNIVERSITY www.cardiff.ac.uk/learn GLASGOW UNIVERSITY www.gla.ac.uk/courses/ openstudies YORK UNIVERSITY www.york.ac.uk/lifelonglearning
and distance-learning courses, helping people to understand what they’ve learned. But out of the 10,000 students who take Heymans’ course, only 1,000 are active on the forums. Another reason to take the course in real-time is the prospect of gaining a qualification. An increasing number of the services offer accredited or verified certificates after you finish all aspects of the course, though there is usually a small fee. In some cases, several courses can be taken together and, once you’ve passed, you can combine them to obtain a MOOC diploma. Unfortunately, no form of online education is without its flaws. MOOCs are vulnerable to plagiarism and cheating, making official bodies wary of recognising any certificates received from them, so if you’re seeking a formal qualification you may wish to look at the alternatives on the opposite page. They also suffer from high drop-out rates. Only half the people who sign up actually go on to watch so much as one video, and less than 10 per cent will finish the course. With few deadlines or fixed meetings, MOOCs are easy to fit around your life and accessible from any time zone, but that also means the classes can be easily postponed and forgotten about. However, for most people, taking an astronomy MOOC is not about gaining a certificate, passing tests or even finishing the entire course. People take MOOCs because they want to learn. Now, thousands of people are taking this new opportunity to expand their knowledge with the help of some of the world’s best teachers. “In the first week, I taught more students than I’ll teach in my entire career at the University of Edinburgh,” said Heymans. “I don’t know what the future of these classes are, but I like the idea of free accessible education for everybody.” S
“What’s great about MOOCs is that you can have courses for a whole range of abilities. People can take the one that’s best for them and then build up.” Catherine Heymans, University of Edinburgh
CASE STUDY Sylvain Chambon, Paris, France Studying: Greatest Unsolved Mysteries of the Universe I read an article somewhere online that said this course was an opportunity to be taught by a Nobel Prize-winning scientist, Brian Schmidt. This is a very compelling argument for MOOCs in general: you can get courses taught by ‘superstar’ professors, or professors that are extremely good at teaching, like Paul Francis. Generally I watch most lectures while commuting to work, then work on the problems in the evenings. As a
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rough approximation it takes up maybe 15-20 hours in a typical week, rising to around 30 hours if a particularly hard problem has been set. That may sound a lot, but it’s mostly just time I would have spent commuting or watching TV, so it’s no real sacrifice. You can decide your own level of involvement, from watching a few lectures here and there to doing all the problems and being active in the discussion forums.
ASTRONOMY EDUCATION AUGUST 45
ACADEMIC ALTERNATIVES If MOOCs aren’t right for you, there are plenty of alternative methods of learning
GCSES
INFORMAL LEARNING
Nearly 3,000 children and adults take a GCSE in astronomy every year. While the majority of people studying the course are schoolchildren, there are dozens of colleges across the country that offer it to mature students. If you can’t find one locally then there are online classes available, though you’ll have to go to an approved centre in order to sit the exam. “I thought a GCSE would be a good entry point into some more serious study as I hadn’t done much astronomy before,” says Gary Chorley, who is taking his GCSE this year after studying at the Western Tutorial College. “I just used to watch things on the TV, like The Sky at Night. I wanted to get into it a bit more seriously and I wanted to learn it in an environment that would be conducive to that. “How much time it takes up really depends on the individual. I want to know stuff, so I’m all for doing a bit of extra work, but there’s no pressure. I’m doing it purely for the love of it.”
Many universities offer courses and evening classes designed for adult learners to fit around their daily lives. They don’t take up too much time and are usually quite cheap. Gordon Stephen Elstow took the Astronomy in Action course at Cardiff University. “It covered different areas to what you would normally cover on an astronomy course,” he says. “They went into great detail. The lectures were about three hours long and the work was a couple of hours a week, so it was very easy to fit around my life.” These courses also allow for a more practical approach, with sessions based on experiments and group discussions that are impossible online but teach vital skills that can be used elsewhere in life. “There were lots of experiments and when you’re with a bunch of other people it really helps,” says Samantha Richards, who took the Science is for Parents Too! course at the University of York. “You can bounce things off each other and clarify things right there and then.”
OPEN UNIVERSITY
SELF-GUIDED STUDY
The Open University is probably the most well known method of distance learning. Taking a degree can be quite expensive, but you don’t need to commit to a full course from the outset. There are several shorter courses that lead to a standalone qualification, which can be upgraded at a later date if you decide to continue. “You need to do a minimum of between eight and 16 hours a week,” says Alistair Bruce who is studying for a PhD at the University of Edinburgh following his OU degree. “I didn’t feel like I was under any pressure to make any decisions early on in the course. It was only towards the very end that I thought, ‘You know what, this is quite a good idea.’ “When I started it was one the few places that was offering a structured course but without forcing you to attend lectures on a regular basis. I might have done an online course but it’s nice to have an end goal in sight.”
If you don’t want to take part in a formal course, there are plenty of other ways to learn about the Universe. Hearing about the latest advances in astronomy is becoming increasingly easy as its popularity rises. There are many websites, with videos and podcasts available to download and watch or listen to at your leisure, so you can easily keep up to date. All around the country astronomical societies and universities run lecture series about all aspects of astronomy, many of which are free. “We ran a presentation at a local school about astronomy that around 220 people came to,” says Sarah Richardson, who is a member of the York Astronomical Society. For an up-to-date listing of the latest talks in your area and coverage of the top astronomy stories, news and podcasts, check out www.skyatnightmagazine.com, where you can find all the latest astronomical discoveries and the best events in your region.
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THE SKY GUIDE AUGUST 47
The Sky Guide
August There are a couple of interesting conjunctions in August. Mid-month, Jupiter and Venus have a spectacular morning encounter in the dawn sky. Then, right at the end of August, the crescent Moon brushes past Saturn in the evening twilight.
PLUS Stephen Tonkin’s PETE LAWRENCE
BINOCULAR TOUR Turn to page 58 for six of this month’s best binocular sights
Written by Pete Lawrence Pete Lawrence is an expert astronomer and astrophotographer with a particular interest in digital imaging. As well as writing The Sky Guide, he appears on The Sky at Night each month on BBC Four.
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Highlights Your guide to the night sky this month This icon indicates a good photo opportunity
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SATURDAY Mercury and Jupiter are currently very close, although only 6.5º to the west of the Sun. It may be possible to see them really low in the northeast just before sunrise. The separation decreases from 1.5º this morning to just over 1º tomorrow morning.
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FRIDAY Noctilucent cloud season typically comes to an end at the start of August, so keep an eye out low in the northwest an hour or two after sunset, or low in the northeast an hour or two before sunrise. See if you can catch a late display of these eerie electric blue night shining clouds.
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TUESDAY Comet C/2014 E2 Jacques passes less than 1º from mag. +6.4 open cluster NGC 1528 in Perseus this evening. See page 51.
17
SUNDAY The Summer Triangle is very prominent at present, and can be seen high in the sky, looking south at around 23:00 BST (22:00 UT). The asterism is formed by the bright stars Deneb, Vega and Altair, the alpha stars of Cygnus, Lyra and Aquila respectively.
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19
20
23
24
25
MONDAY Mag. –1.6 Jupiter and mag. –3.8 Venus are in conjunction before sunrise. Both are bright and should be easy to spot if the sky is clear. This morning they appear separated by just 12 arcminutes – less than half the apparent diameter of the Moon. See page 50.
SATURDAY It’s worth getting up early to spot Jupiter and Venus, together with a slender waning crescent Moon (5% lit) low in the east-northeast before sunrise. Look for them from 04:45 BST (03:45 UT) onwards.
PETE LAWRENCE X 6
26
TUESDAY X The Milky Way is well placed. Passing virtually overhead at 23:00 BST (22:00 UT), the integrated light from the billions of distant stars in our Galaxy appears to flow down the spine of Cygnus. Here it splits in two thanks to an intervening dark dust cloud.
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TUESDAY Comet C/2014 E2 Jacques starts its photogenic journey across the region of sky occupied by the Heart and Soul Nebulae in Cassiopeia, which are catalogued as Sh2-190 and Sh2-199 respectively. See page 51.
SUNDAY Following yesterday’s Jupiter-VenusMoon conjunction, see if you can spot an even thinner waning crescent Moon (1% lit) in this morning’s dawn sky. It’ll be even closer to the Sun. Take care and stop searching when the Sun appears above the horizon.
WEDNESDAY With the Moon out of the way in the middle of the night, this is a great time to go planetary nebula hunting in this month’s Deep-sky tour. See page 56.
MONDAY Mag. +0.6 Mars is 3.5º south of mag. +0.9 Saturn. Both planets are visible low in the southwest as the sky begins to darken.
28
THURSDAY Comet C/2014 E2 Jacques passes the open cluster M52 in Cassiopeia. At its closest, the comet will be around 3º from this deep-sky object.
THE SKY GUIDE AUGUST 49
What the team will be observing in August
3
10
SUNDAY Today’s full Moon coincides with lunar perigee, the point when the Moon is closest to us in its orbit. This month’s Moon is the joint largest of the year at 33 arcminutes and 28 arcseconds. It shares this accolade with the full Moon that occurred on 1 January.
SUNDAY The almost first quarter Moon lies between Mars and Saturn this evening.
13
WEDNESDAY X The Perseids peak at 01:00 BST (00:00 UT), but the presence of an almost full Moon not far from the radiant makes conditions unfavourable. Don’t be put off though: on page 60 we tell you how you can still image them.
Pete Lawrence “I’ll be trying to get photos of all the amazing conjunctions happening this month. The close encounter between Venus and Jupiter mid-month should be spectacular against the bright dawn sky.” Stephen Tonkin “This month my favourite asterism, Kemble’s Cascade, is at an easy altitude for binoculars after twilight ends, when it appears to be tumbling vertically into the ‘splash pool’ of NGC 1502.” Steve Marsh “I missed comet C/2011 L4 PANSTARRS in March 2013 so I’m going to try and get a glimpse of C/2014 E2 Jacques this month to make up for it.”
Need to know
The terms and symbols used in The Sky Guide
22
FRIDAY Comet C/2014 E2 Jacques passes mag. +3.4 Epsilon (¡) Cassiopeiae, the star that marks the eastern end of the W-shaped constellation. There’s a photo opportunity for a wide field shot here, as this part of the sky is full of open clusters. See page 51.
UNIVERSAL TIME (UT) AND BRITISH SUMMER TIME (BST) Universal Time (UT) is the standard time used by astronomers around the world. British Summer Time (BST) is one hour ahead of UT.
RA (RIGHT ASCENSION) AND DEC. (DECLINATION) These coordinates are the night sky’s equivalent of longitude and latitude, describing where an object lies on the celestial ‘globe’.
HOW TO TELL WHAT EQUIPMENT YOU’LL NEED NAKED EYE Allow 20 minutes for your eyes to become dark-adapted
BINOCULARS 10x50 recommended
PHOTO OPPORTUNITY Use a CCD, planetary camera or standard DSLR
SMALL/MEDIUM SCOPE Reflector/SCT under 6 inches, refractor under 4 inches
LARGE SCOPE
31
W SUNDAY The Moon and Saturn are in conjunction this evening, the mag. +0.9 planet appearing just over 0.5º from the Moon at around 20:30 BST (19:30 UT) as the sky darkens. See page 50.
Reflector/SCT over 6 inches, refractor over 4 inches
Getting started in astronomy If you’re new to astronomy, you’ll find two essential reads on our website. Visit http:// bit.ly/10_Lessons for our 10-step guide to getting started and http://bit.ly/First_Tel for advice on choosing your first scope.
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50
DON’T MISS…
3 top sights
A month of conjunctions WHEN: Various dates throughout the month 2 and 3 August at 05:00 BST (centre of UK)
16-20 August at 05:00 BST (centre of UK)
Venus 16 Aug
10º
10º
M44 Venus
Mercury 2 Aug Mercury 3 Aug
Jupiter 20 Aug
Jupiter SAFE SOLAR OBSERVING
23 and 24 August at 05:20 BST
31 August at 21:00 BST Moon
10º
Jupiter
23 Aug 24 Aug
Venus
Mars 10º
Moon 23 Aug
M44
Iota Librae
Saturn Alpha Librae
Moon 24 Aug
Five of the major planets plus the thin crescent Moon are involved in a slew of conjunctions this month
PETE LAWRENCE X 4
A CONJUNCTION OCCURS when two or more bodies appear, by line of sight, close to one another in the sky. The formal definition of a conjunction is when both bodies share either the same right ascension or same ecliptic longitude – part of a coordinate system based around the Sun’s apparent path. Neither of these necessarily coincide with the moment when both bodies appear closest; a point in time known as an appulse.
!
NEED TO KNOW
The size of objects in the sky and the distances between them are measured in degrees. The width of your little finger at arm’s length spans about 1º.
skyatnightmagazine.com 2014
The first conjunction occurs between Mercury and Jupiter. They may be seen popping up over the northeast horizon just before sunrise on the 2nd and 3rd. A flat horizon in this direction really helps. Both objects are fairly bright at mag. –1.6, but they are only 6.5º west of the Sun, so exercise caution when looking for them. An easier conjunction occurs on 18 August, when Jupiter meets Venus in the dawn sky. This should be spectacular, as they will be separated by just 12 arcminutes, which is less than half the apparent diameter of the Moon. A flat northeast horizon is once again useful, but mag. –3.8 Venus will be something of a beacon even
against the bright dawn sky. There’s an extra bonus here because both objects will be just to the south of M44, the Beehive Cluster in Cancer. The brightening sky will make the cluster stars hard to see,
but it’s still worth having a look with a pair of binoculars. On 23 and 24 August, the waning crescent Moon joins the now more separated planets. Jupiter and Venus will be 5º apart at this time. On the 23rd, the waning crescent Moon (5% lit) is 7º below and right of Jupiter. The view on the 24th is a little more taxing, as the Moon will be thinner at just 1% illumination and lower down, rising just an hour before the Sun. Low in the southwest on the evening of the 25th, Mars and Saturn appear separated by just 3.5º. Look out for the colour contrast between orange, mag. +0.6 Mars and yellow, mag. +0.9 Saturn. Both planets stay relatively close together for the rest of the month and on the evening of the 31st are joined by a waxing crescent Moon (33% lit). In fact the Moon passes very close to Saturn. Appulse occurs around 20:30 BST (19:30 UT) in darkening skies. The separation seen from the centre of the UK at this time is 32 arcminutes centre to centre, placing Saturn 17 arcminutes off the northern edge of the Moon. Bright beacons Venus and Jupiter will be just south of M44 on the 18th
THE SKY GUIDE AUGUST 51
Comet C/2014 E2 Jacques WHEN: All August, Moon interferes mid-month
AT THE TIME of writing, comet C/2014 E2 Jacques looks as if it’s going to outperform its initial brightness estimates and appear just below the threshold of naked-eye visibility throughout August. Despite the lack of hype, this comet could turn out to be a great target for small telescopes and binoculars. From the UK, the comet becomes well placed during August, passing out of Auriga and into Perseus before heading up through Camelopardalis, Cassiopeia and finally into Cepheus. It’s also circumpolar from the UK, meaning it’ll always be above the horizon. Throughout this period it should be around mag. +6.5, so not quite a naked-eye comet, but certainly one that should be a fairly easy to spot
with binoculars assuming its brightness holds. The comet passes west of the Kids asterism in Auriga on 4-7 August. On the 12th and 13th it can be found close to open clusters NGC 1545 and NGC 1528 in Perseus. There will be a good imaging opportunity on 19-21 August, when the comet will cross in front of the Heart and Soul Nebulae in Cassiopeia. On 22-23 August it will be close to mag. +3.3 Epsilon (¡) Cassiopeiae, which marks the eastern end of the famous W pattern. Finally, on 31 August, the comet passes into nebula IC 1396, which sits at the bottom of the House asterism in Cepheus. At 01:00 BST (00:00 UT) on the 31st, the comet is right next to Herschel’s Garnet Star, mag. +4.2 Mu (+) Cephei.
IC 1396
DRACO CEPHEUS
LACERTA
31 Aug
+
Herschel’s Garnet Star
House URSA MINOR 26 Aug
ANDROMEDA
Polaris
M31
C/2014 E2 Jacques
CASSIOPEIA W ¡
21 Aug
CAMELOPARDALIS
19 Aug
Heart Nebula Soul Nebula TRIANGULUM
16 Aug
Mirphak Algol
NGC 1528 NGC 1545
Capella
Kids
11 Aug
PERSEUS
ARIES
6 Aug Pleiades
1 Aug
TAURUS Hyades
Elnath
Aldebaran
NE
The comet’s path: positions correct for 01:00 BST (00:00 UT) on dates shown
August meteors WHEN: Various dates throughout the month
IT’S AUGUST, WHICH means meteor season is upon us once again. The Perseids reach their peak at 01:00 BST (00:00 UT) on the 13th, but this year there’s going to be a bright waning gibbous Moon (92% lit) up all night and unfortunately spoiling the show. There’s no doubt that the Moon will have an effect on the number of meteors seen visually, but bright trails can still be seen even through the Moon’s glare. Meteor photography is also possible, but takes a bit of
!
NEED TO KNOW
The zentihal hourly rate of a meteor shower is the expected number of meteors seen under perfect conditions with the radiant point of the shower overhead.
tweaking to adjust to the bright conditions. Turn to page 60 for details. There are other minor showers active at this time of year too. These include the Northern Iota Aquariids (11 August to 10 September), which peak on 25/26 August; the Southern Iota Aquariids (1 July to 18 September), which peak on 6/7 August; and the Northern Delta Aquariids (16 July to 10 September), which peak on 13/14 August. At the start of the month the Alpha Capricornids (15 July to 11 September, peak 1/2 August) are a decent bet as the waxing crescent Moon (29% lit) sets before darkness takes hold. This shower has a good
You should be able to see bright Perseid trails despite the Moon
proportion of bright, slow meteor trails. Also keep an eye out for Kappa Cygnids
(26 July to 1 September, peak 18 August) which can appear with blue-white trails. skyatnightmagazine.com 2014
52
PEGASUS
The planets
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PICK OF THE MONTH e
PISCES
URANUS
PETE LAWRENCE X 3
BEST TIME IN AUGUST: 31 August, 03:30 BST (02:30 UT) ALTITUDE: 42º LOCATION: Pisces DIRECTION: South RECOMMENDED EQUIPMENT: Binoculars, small scope FEATURES OF INTEREST: Colour, very subtle banding with larger instruments. As the night sky returns to full darkness after June and July, it’s the outer planets Neptune and Uranus that are holding the Solar System baton. Uranus is still a couple of months from opposition, which this year occurs on 7 October. Even so, the planet does manage to reach its highest point in the sky, due south in darkness towards the end of August, and this is the best time to observe it.
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You can find Uranus using the trio of stars just below Epsilon (¡) and Zeta (c) Piscium
Uranus doesn’t give up its secrets easily. Being so distant, the planet appears small in our skies at just 3 arcseconds across, but it’s still possible to make out the planet’s tiny disc even with small instruments. At mag. +5.8, Uranus is theoretically visible to the naked eye, but reaching a high point of only 40 º means that it’s normally obscured by the slight murk found closer to the horizon. You’ll need a telescope to reveal The planet is currently located Uranus’s colour to the south of a pair of 4th-
magnitude stars, Epsilon (¡) and Delta (b) Piscium. This month it’s slightly closer to the former. While our eyes may struggle, Uranus is an easy binocular target. Look to the east of Epsilon Piscium to locate mag. +5.2 Zeta (c) Piscium. Below these stars is a faint triangle formed by 73, 77 and 80 Piscium. Uranus is the brightest object off to the right of this pattern. A small telescope will reveal the most intriguing aspect of this distant world: its colour. Where binoculars will make Uranus look nothing more like a faint star-like point, devoid of hue, a telescope shows it to be a beautiful green. The disc of Uranus doesn’t show much in the way of detail. What is there tends to show as subtle banding which may be visible using large instruments at high magnification.
THE PLANETS IN AUGUST The phase and relative sizes of the planets this month. Each planet is shown with south at the top, to show its orientation through a telescope VENUS 15 August
MARS 15 August
JUPITER 15 August
SATURN 15 August
URANUS 15 August
NEPTUNE 15 August
MERCURY 1 August
MERCURY 15 August
MERCURY 31 August 0”
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10”
20” 30” 40” ARCSECONDS
50”
60”
MERCURY BEST TIME IN AUGUST:
1 August, 05:00 BST (04:00 UT) ALTITUDE: 2º (low) LOCATION: Cancer DIRECTION: Northeast Mercury is a morning object at the start of August, rising shortly before the Sun. The planet is around mag. –1.5 and this will help it to stand out against the morning twilight. On the 3rd, Mercury and Jupiter (both around mag. –1.6) are separated by just over 1º. Superior conjunction occurs on the 8th; it should be visible in the evening sky from mid-month. On 14 August, the planet is mag. –1.2 and sets 30 minutes after the Sun. Its position worsens from here.
telescope, measuring just 7 arcseconds across on the 1st and shrinking to 6 arcseconds by the 31st.
S AT U R N ’S M O O N S
August
JUPITER BEST TIME IN AUGUST: 18 August, from 05:00 BST ALTITUDE: 7º (low) LOCATION: Cancer DIRECTION: East-northeast
A close conjunction with Mercury occurs on the morning of 3 August, both planets being around mag. –1.6 and rising 40 minutes before the Sun. Jupiter improves slowly throughout the month, the highlight being the close meeting with Venus on the 18th, which occurs just south of M44 in Cancer in the dawn twilight.
Using a small scope you’ll be able to spot Saturn’s biggest moons. Their positions change dramatically during the month, as shown on the diagram. The line by each date on the left represents midnight. DATE
2 3 4 5 6
8
VENUS
BEST TIME IN AUGUST:
BEST TIME IN AUGUST:
31 August, from 20:30 BST (19:30 UT) ALTITUDE: 12º LOCATION: Libra
10
DIRECTION: Southwest
12
Saturn is an evening object, close to mag. +2.8 Zubenelgenubi (Alpha (_) Librae). The planet is mag. +0.9 which makes it hard to see against the bright evening twilight. Look out for the conjunction with the Moon on 31 August; at 20:30 BST (19:30 UT), the planet will be about 17 arcminutes north of the Moon’s northern limb.
BEST TIME IN AUGUST: 1 August, 23:30 BST (22:30 UT) ALTITUDE: 8º (low) LOCATION: Virgo DIRECTION: Southwest
Mag. +0.4 Mars sits in the evening twilight, low down in the southwest as the sky darkens. The planet is heading east and passes close to Saturn during the last week of August. Mars is now rather small through a
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13 14 15 16 17 18 19 20
NEPTUNE BEST TIME IN AUGUST:
MARS
EAST
7
SATURN
1 August, from 04:00 BST (03:00 UT) ALTITUDE: 3º (low) LOCATION: Gemini DIRECTION: Northeast Venus rises two hours before the Sun on 1 August. Despite an impressive magnitude of –3.8, it’s circumstances aren’t good for telescopic viewing: the planet has a small, 10-arcsecond disc (92% lit) that shows little detail. A close encounter with Jupiter occurs on the 18th. The two planets will be joined by the waning crescent Moon on the mornings of 23rd and 24th.
WEST
1
29 August, 01:00 BST (00:00 UT) ALTITUDE: 27º LOCATION: Aquarius DIRECTION: South
Neptune is up all night at the end of August, reaching opposition on the 29th. At mag. +7.8, the planet is an easy binocular target. Slowly drifting through Aquarius, Neptune ends the month just 42 arcminutes northeast of mag. +4.8 Sigma (m) Aquarii.
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2
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See what the planets look like through your telescope with the field of view calculator on our website at: http://www.skyatnightmagazine.com/astronomy-tools
0
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arcminutes
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Dione
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Titan
Iapetus
Saturn
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The Northern Hemisphere RT O N
HOW TO USE THIS CHART
GLOBULAR CLUSTER
1. HOLD THE CHART so the direction you’re facing is at the bottom. 2. THE LOWER HALF of the chart shows the sky ahead of you. 3. THE CENTRE OF THE CHART is the point directly over your head.
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25 Aug 2014, 06:05 BST
13 Aug 2014, 21:40 BST
29 Aug 2014, 10:25 BST
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SUNDAY
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FIELD OF VIEW
11
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THE MOON IN AUGUST*
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PE
CONSTELLATION NAME
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STAR NAME
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1 AUGUST AT 01:00 BST 15 AUGUST AT 00:00 BST 31 AUGUST AT 23:00 BST
HE A ST
STAR CHARTS
WHEN TO USE THIS CHART
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THE SKY GUIDE AUGUST 55
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Deep-sky tour Look beneath the wings of Cygnus and you’ll find some great sights for your telescope �
Tick the box when you’ve seen each one
NGC 6811 has a sparse centre compared to its edges
3
4
1
CHART AND PHOTO: PETE LAWRENCE
2
THE BLINKING NEBULA
NGC 6826 is a mag. +8.9 planetary nebula located on the trailing edge of Cygnus’s western wing. It’s 25 arcseconds across with a bright, mag. +10.7 central star, which is easy to see at around 150x magnification. A 6-inch scope shows the star to be surrounded by a more or less circular haze, while larger apertures show the haze to be elliptical at 250x magnification. Looking straight at the bright central star overwhelms the view and the nebula disappears. If you move your eye around the field, averted vision places the object’s delicate light on a more sensitive part of your retina and the nebula blinks back into view; hence the Blinking Nebula. � SEEN IT
NGC 6833
The star-filled plane of the our own Milky Way flows down through Cygnus, which means we can to see lots of ‘local’ objects such as clusters and planetary nebulae in this part of the sky. Located 1.75º to the southeast of our first target is NGC 6833, another planetary nebula. At just 3 arcseconds across this one is tiny, but it is visually distinctive because of its strong green colour – it looks like a green star. A 6-inch telescope should pick it up fairly easily and as usual don’t be afraid to pile on the magnification. NGC 6833 is easier to detect with the use of an OIII filter. � SEEN IT
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6
NGC 6884
Stop three is also a planetary nebula. NGC 6884 is located just over 4º southeast of NGC 6833: extend a line from Omicron2 (k2) Cygni to Omicron1 (k1) Cygni, then head southwest for two-thirds that distance again. NGC 6884 can be a bit of a challenge because it’s visually small, with an apparent diameter of around 6 arcseconds. It’s also relatively faint at mag. +13.0. Presented against the background of the Milky Way itself, it’s quite easy to get lost on the way. NGC 6884 has a blue-green colour and responds well to the use of an OIII filter. The nebula is estimated to be 6,000 lightyears away and is artificially dimmed by intervening dust in the Milky Way. � SEEN IT
NGC 6866
Head 2.75º southwest of NGC 6884 to reach open cluster NGC 6866. With an apparent diameter of 7 arcminutes and listed at mag. +7.6, this is a fairly easy target for a small telescope. A 6-inch instrument reveals a number of resolved stars, with a misty hint of more in the background. A number of the stars appear drawn out into lines or strings and this is especially evident close to the centre of the cluster. With larger apertures come a greater number of resolved cluster stars; it also becomes evident that NGC 6866 is clumpy, appearing as several smaller groups of stars with darker gaps in between. � SEEN IT
NGC 6811
Open cluster NGC 6811 is the brightest of this month’s objects at mag. +6.8. It’s located just less than 2º to the northwest of mag. +2.8 Rukh (Delta (b) Cygni. A 6-inch scope resolves about 50 stars spread over an area measuring 20 arcminutes across. This is a pretty cluster, the core of which shows a somewhat square or slightly pentagonal shape. The core of NGC 6811 appears sparse compared to the outer part of the pentagon and this has led to the nickname of ‘The Hole in the Cluster’. Roughly two-thirds the apparent diameter of the Moon, NGC 6811 is best seen with a low magnification of around 50-75x. � SEEN IT
ABELL 61
Abell 61 is a relatively large but faint planetary nebula best suited for large apertures or imaging. It measures 3.4 arcminutes across and is mag. +13.5; however, its large size means that its light is spread across a sizeable area, resulting in a low surface brightness. Abell 61 is best seen with a 12-inch or larger instrument and an OIII filter is recommended. The nebula looks like a perfectly circular disc with uneven illumination. The west side is brighter, a fact that stands out well when using averted vision. From NGC 6811, use your setting circles to slew 18 minutes of right ascension to the west; use the small triangular pattern of 8th-magnitude stars slightly northwest of Abell 61 to confirm its location. � SEEN IT
+50°
+55° 20
20
t
h
h3
0m
t
+55°
s
CYGNUS k
1 NGC 6826
k
3
f
2
NGC 6884
19 h3
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NGC 6833
+45°
+50°
4NGC 6866 NGC 6811
h
b 20
Rukh
5
2º
E
N
1º
Abell 61
6
W
S +40°
+45°
LYRA
19
+40°
h3 0
m
NGC 6819
Polaris
Collinder 463
NGC 654
E
l
CEPHEUS
_
N
5º
27 Aug
a
C/2014 E2 Jacques
URSA MINOR
W
Segin
S
Caph `
Eddie’s Coaster
35 Ruchbah
5
CASSIOPEIA _ NGC 281
a
M31
b
M103 NGC 457
44
¡
4
NGC 663
a
Schedar
2
3
22 Aug
Collinder 464
1
NGC 659
ANDROMEDA
Stock 2
Sh2-190
Melotte 15
h
r
Double Cluster
Sh2-199 Collinder 33
CAMELOPARDALIS
Trumpler 2
a
_
Almach
a
¡
17 Aug
`
M34
6
Mirphak
_
Melotte 20
LYNX
NGC 752
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TRIANGULUM `
NGC 1528 NGC 1545
PERSEUS
`
b
Algol
12 Aug
Binocular tour An amateur’s asterism, a terrific trio and a rare hypergiant mark the night sky in August
With Tick the box when you’ve seen each one Stephen Tonkin �
1 RHO CASSIOPEIAE
CHARTS AND PICTURES: PETE LAWRENCE
10 x Rho (l) Cassiopeiae is an unusual type of 50 star of which only a dozen are known: a yellow hypergiant. If it were where our Sun is, it would extend beyond the orbit of Mars. It is classed as a semi-regular variable, normally ranging between mag. +4.6 and +5.4, but every 50 years or so it reddens and falls below 6th magnitude. The last time this happened was in 1946, so it’s overdue to happen again. The star is also thought to be nearing the end of its life, so is a good supernova candidate. � SEEN IT
2 EDDIE’S COASTER
15 x Surely destined to become a binocular 70 classic, Eddie’s Coaster is an asterism that is not easily apparent in star charts or images, but which is very obvious (and very beautiful) in 10x50 binoculars. To find it, look 3° north of mag. +2.2 Gamma (a) Cassiopeiae. You will find a 3°-long wave of 7th- and 8th-magnitude stars, reminiscent of a roller-coaster, hence the second part of its name. The first part is in honour of
skyatnightmagazine.com 2014
amateur astronomer Eddie Carpenter, who has been delighting those people to whom he has shown it for many years. � SEEN IT
3 35 CASSIOPEIAE
10 x Imagine that mag. +3.4 Segin (Epsilon (¡) 50 Cassiopeiae) and mag. +2.7 Ruchbah (Delta (b) Cassiopeiae) form the base of an equilateral triangle: surrounding the third point of this triangle is another, an isosceles triangle of 6th-magnitude stars that covers less than one square degree of sky. The most easterly of these, pointing back towards Segin, is mag. +6.3 35 Cassiopeiae. It has a mag. +8.4 companion that is a easy to split in 10x50 binoculars, nearly an arcminute to the north. The primary star is white, but see if you can detect any colour in the companion. Comet C/2014 E2 Jacques passes close by on the 23rd; see page 51. � SEEN IT
4 CASSIOPEIA TRIPLE CLUSTER
15 x Perseus has the Double Cluster, but 70 Cassiopeia has a triple! Imagine a line
between Segin and Ruchbah: the richest of these clusters, NGC 663, sits 1º below its mid point; its four brightest stars appear to be separated into pairs by a dark lane. About 0.75° to the north-northwest is NGC 654, a comet-shaped patch of light just next to a mag. +7.3 star. The poorest of the trio is NGC 659, a tiny ghostly glow which may need averted vision to spot – look just to the NGC 663 side of the mag. +5.8 star 44 Cassiopeiae. � SEEN IT
5 MELOTTE 15
15 x In 15x70 binoculars open cluster Melotte 15 70 appears about the same size as NGC 663, but it is much sparser. You should notice that the brightest stars form a V near the centre of the cluster and that, even with averted vision, only a few more fainter stars can be seen scattered through it. Unless you have exceptional skies, do not expect to see even a hint of the Heart Nebula, which surrounds the cluster. On the 20th, comet C/2014 E2 Jacques will be a tricky object 1° to the northwest at the end of twilight. � SEEN IT
6 BETA CAMELOPARDALIS
10 x Mag. +4.0 Beta (`) Camelopardalis has 50 a mag. +7.4 companion 84 arcseconds to the southwest that is very easy split in small binoculars, but this is not its main appeal. Beta Camelopardalis is a yellow supergiant, transitioning between being a hot new blue star and a red supergiant. Enigmatically, it has been seen to brighten by a whole magnitude in a flash lasting for one quarter of a second, possibly its equivalent of huge solar flares. � SEEN IT
THE SKY GUIDE AUGUST 59
N
STATISTICS
Moonwatch Flamsteed
FLAMSTEED IS A small crater in the Oceanus Procellarum, the Ocean of Storms. The crater is not particularly prominent, but does sit in an interesting region. It can be seen with a small scope; a larger one will show that its rim isn’t perfectly circular, with a bulge towards the south. Its walls are well defined, with a difficult to see terraced region close to the southern bulge. Flamsteed is relatively easy to find as it sits at the centre of a triangle formed by the darkfloored crater Grimaldi (222km wide), ray crater Kepler (31km) and crater Gassendi (111km). Midway between the fractured floor of Gassendi and Flamsteed lies the Letronne bay region, the southern boundary of Oceanus Procellarum. Crater Letronne (119km) shows a partial three-quarter rim, the northern part having succumbed to the ocean’s lava flows. Head north from Letronne and you’ll encounter a line of small but distinctive craters. The first, 75km north of its centre, is Flamsteed A (11km). Continue 65km further north to reach Flamsteed B (10km). Next in line is Flamsteed itself; 45km further north still and topping the line off is Flamsteed D (6km), which should be visible with a 4-inch scope. If you were wondering where Flamsteed C had got to, it is the bright 9km crater west and slightly south of Flamsteed. The most remarkable feature in this region is 100km ghost crater Flamsteed P. All that remains of it is a broken ring, the remnant of a crater that has been completely flooded with lava. Under direct sunlight, conditions you’d get around a full or gibbous Moon, Flamsteed P is visible because
its rim appears brighter than the surrounding dark lava. When the terminator is close by and the lighting is oblique, the slightly raised peaks of Flamsteed P’s rim cast shadows across the Oceanus Procellarum’s floor. They’re not particularly dramatic but sufficient to give Flamsteed P more presence. Flamsteed itself sits dominantly on the southern wall of Flamsteed P. More ghost craters can be seen to the west in the form of Flamsteed G (46km) and
TYPE: Crater SIZE: 22km AGE: 1.1-3.2 billion years old LOCATION: Latitude 4.5°S, longitude 44.3°W BEST TIME TO OBSERVE: 7-21 August MINIMUM EQUIPMENT: 2-inch telescope
E
Flamsteed T (24km). This is a complicated region of crater flooding, pockmarked with younger, smaller craters. Flamsteed G has lost its western side completely to the lava while Flamsteed T maintains its rim to the east and west but
has lost any semblance of itself to the north and south. The net result is a feature that resembles a closed pair of brackets. Another ghost crater can be seen 170km southeast of Flamsteed; this is 62km Wichmann R.
“All that remains of ghost crater Flamsteed P is a broken ring” KEPLER
FLAMSTEED D FLAMSTEED P
FLAMSTEED T GRIMALDI
FLAMSTEED
FLAMSTEED G
WICHMANN R
FLAMSTEED C FLAMSTEED B
WICHMANN
FLAMSTEED A LETRONNE
GASSENDI
Flamsteed and its entourage can be found at the centre of a triangle formed by Grimaldi, Gassendi and Kepler
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60
Astrophotography Meteors by moonlight RECOMMENDED EQUIPMENT DSLR camera, wide lens (focal length less than 50mm), shutter release cable, tripod
ALL PICTURES: PETE LAWRENCE
A moonlit meteor vista: before and after processing
METEORS SHOWERS HAVE two natural enemies: the weather and the Moon. In the UK at least, getting both to behave is something of a lottery. This year, the famous Perseid meteor shower will be affected by a bright waning gibbous Moon. There’s not much any of us can do about the effect the Moon has on the sky, but we can diminish its effects on our photos, which is what we’re going to look at this month. The Moon reflects sunlight; in terms of the sky it acts like a dimmer version of the Sun. Using a wide lens, try taking a long exposure of the view outside, including some sky, when there’s a bright Moon visible. Eventually, the colours build on the camera sensor to give you a picture that looks like it was taken in the middle of the day. Amazingly, the sky also starts to go blue too. When there’s a bright Moon above the horizon, the blue component of the reflected sunlight scatters across the sky, just like direct sunlight does during the day. In the day, the reason why stars are not readily skyatnightmagazine.com 2014
visible to the naked eye is that the scattered blue light raises the sky brightness threshold and the delicate starlight is swamped. The effect happens with moonlight too, but as the Moon’s light is dimmer, it’s not so severe. If you look up in the sky when there’s a bright Moon about, it is possible to see some of the brighter stars with the naked eye, but the dimmer ones become hard to see. The same happens with meteors. Visually, this month’s Perseid shower will suffer because the fainter meteors will be hidden from view. However, it’s still possible to see bright meteors, as long as they are able to stand out above the sky threshold. Photographing a meteor shower under the influence of bright moonlight can be done, but the yield will tend to be lower, with only the brightest trails standing out. The technique described here
works for tracked camera mounts or static tripod setups. Meteor photography has been revolutionised by digital imaging. Back in the days of film, each exposure was typically several tens of minutes long. For a digital camera, exposures of 30-60 seconds are best suited to capturing meteors. Make the exposure too long and unless you live in a very dark sky site, the background of your images will oversaturate thanks to light pollution. For moonlight meteor photography the same is true, except that oversaturation occurs much quicker because the sky is lit by the Moon. The solution to the problem is to take exposures that don’t oversaturate. As this is normally pretty short, a compromise has to be made where the sky is allowed to get brighter than you’d normally want for dark-sky meteor imaging. As long as you avoid a white out, then it’s possible to correct the image during processing and obtain some good shots of the brighter trails. It’s essential to make sure the Moon isn’t in, nor can move into, the field of view of your camera. If it does, it’ll create a whiteout zone close to it and introduce lens flare in the frame. Aiming in the opposite direction is ideal. If that’s not practical, point as far away from the Moon’s disc as you can, taking into consideration that it moves east to west throughout the night.
KEY TECHNIQUE SAVED BY PROCESSING Sometimes it’s just a fact of life that the conditions just aren’t going to be perfect, and a Moon-soaked sky certainly fits that bill as far as meteor imaging is concerned. However, as long as there are no overexposed areas, it’s often possible to tweak an image back to some semblance of normality. This month’s we’re looking at how to recover such an image using levels adjustment. It’s amazing what can be recovered, and understanding how levels can be made to work for you is an invaluable skill in many areas of astrophotography.
Send your image to:
[email protected]
THE SKY GUIDE AUGUST 61
STEP-BY-STEP GUIDE STEP 1
STEP 2
The basic setup for moonlight meteor photography is exactly the same as for normal meteor photography. Use a wide, fast lens with a 50mm or shorter focal length. F/2.8 or faster is ideal. A simple tripod mount is fine, though a tracking mount will allow you to stick to the same area of sky. A shutter release cable is also required to automate the shooting sequence.
Carefully pre-focus the lens at infinity. Use Live View on a bright star if your camera supports it. Fully open the lens and set the ISO to a high value (around 1600). You’ll need to set the shutter mode to continuous shooting. This will mean that non-bulb exposures will repeat over and over when the shutter button is locked down via the remote shutter release cable.
STEP 3 Set a short exposure of 10 seconds. Take one shot and check the image on your camera’s review screen; most have an information button, which will display details about the image including any areas of overexposure. If your camera has a histogram display, bring that up and examine the graph. What you’re trying to avoid here are areas of white in the image – these areas are overexposed.
STEP 4 If the result is close to white, or even showing white (this will appear in the histogram as a sharp ‘cliff’ in the graph towards the white end) then the camera’s sensitivity needs to be lowered: reduce the ISO or stop the lens down. If the exposure doesn’t come out as pure white, consider increasing the ISO or using a longer exposure.
STEP 5 Aim at a point about two-thirds up the sky, in a direction away from the Moon. Lock the shutter button down on the release cable and leave the camera to do its thing. Regularly check and replace the battery and memory card as required. Download the contents of the memory card onto a computer and check each image for trails. If you find one, rename the file and continue checking.
STEP 6 Open a trail image in Photoshop or GIMP. Call up the levels adjustment and drag the black point so it sits at the base of the histogram. If your sky is light-polluted, examine the histogram for each colour channel and repeat the process. Click ‘Ok’ after each adjustment. Finally, adjust the mid-point control towards the white end of the graph to suit. skyatnightmagazine.com 2014
Dealing
deluge with the
THINKSTOCK X 2
HOW ASTRONOMY IS MEETING THE CHALLENGE OF BIG DATA
Paul F Cockburn explores the ways computers have evolved to handle the huge quantities of data generated by today’s astronomical surveys
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C
omputers have long played an important role in astronomy. It’s just that, back in the late 19th and early 20th centuries, the word was applied to people rather than machines – specifically to the men and women who carried out repetitive calculations on data derived from some of the earliest photographic surveys of the night sky. At the time, Harvard College Observatory, under the directorship of Edward C Pickering, was at the forefront of extracting information from recorded data. With the help of Mina Fleming, Pickering was able to classify thousands of stars based on the spectra of their light. Meanwhile Fleming’s ‘computing’ work enabled her to ‘discover’ the Horsehead Nebula. Pickering and Fleming would undoubtedly be amazed by the richness of today’s astronomical observations, which, thanks to the advances in computers, telescopes and detectors, can be made across the entire electromagnetic spectrum. It’s fair to say, however, that such advances would not be possible without the parallel development of information technology. “Computerisation has had an impact on everything, from the control of instruments and the telescopes themselves, all the way through to handling and interpreting the data,” says Nigel Hambly of the Institute for Astronomy at the University of Edinburgh. “Today, the software engineer is an extremely important member of the astronomical team.” Hambly and his colleagues at the Royal Observatory, Edinburgh, are currently involved in several major projects that are generating huge amounts of data, most notably ESA’s Gaia project, which aims to chart a three-dimensional map of our own Galaxy. It’s a project that’s
expected to generate about 1,000 terabytes (or one petabyte) of data – enough to fill more than 200,000 DVDs.
Storage hunters If the number, range and quality of observations continues to increase, are astronomers in danger of having more data than they can cope with? Hambly doesn’t think so. “In my experience, during the last 20 years, the ambition of what astronomers have tried to do has always been what’s pushed the available technology along. In terms of IT, there’s been such an exponential growth in processing power and storage capacity that our ambitions have been able to become much grander. “When I first started in astronomy a couple of decades ago, data storage was enough of an issue that sometimes the data for an
Þ Harvard College Observatory’s ‘computers’ hard at work around the turn of the 20th century þ Gaia’s bid to create a 3D map of our galaxy will produce a huge amount of data
SURVEY SIZE PAST
PHOTOGRAPHIC PLATES Once the only way of taking astrophotos, photographic plates take up 400MB when digitised, a little more than half a CD.
PRESENT
HERSCHEL SPACE OBSERVATORY Over the entire lifetime of the mission, Herschel transmitted over 3TB of data, enough to fill 4,300 CDs.
FUTURE
The amount of data astrophotography has produced since it began has grown rapidly
SQUARE KILOMETER ARRAY Once completed, the SKA will generate more data every day than the entirety of the internet.
skyatnightmagazine.com 2014
DATA FLOW AUGUST 65
COMPUTING POWER What equipment do you actually need to crunch the numbers? surprising that the ALMA site suggests that only the smallest data sets “can be effectively processed on a laptop” and that, for desktop computers, 8GB “is probably the minimum memory (RAM) needed” to process the data into something usable. To take on the full data set, however, takes a lot more processing power than a single computer is capable of. To tackle surveys that
Even high-end laptops are unable to cope with all but the smallest data sets produced by ALMA
The stages of image processing sift through the data to produce a clearer image of galaxy M100
RAW
The computer clusters needed to crunch the largest and most complex data sets can fill entire rooms
experiment would be processed in real-time and the raw data stream would then be discarded,” he explains. “Now data storage is less of an issue because the technology has come on in leaps and bounds. Today we can archive raw measurements so that we always have the possibility of going back to look at them.” Hambly’s colleague Michael Read works chiefly on archiving data derived from the panoramic surveys of the southern skies provided by ESO’s VISTA (Visible and Infrared Survey Telescope for Astronomy) project in Chile. While he doesn’t deal with the raw data – the photographic images are ‘cleaned up’ in Cambridge first – Read is very much involved with the further processing of the images and entering the data from them into
AFTER PROCESSING
can be terabytes in size requires huge server farms. ALMA suggests that you need over 100GB of RAM. All of this can cost over £50,000 to set up, and running costs only add to the bill. On top of power and cooling costs, dedicated staff and training make dealing with these huge data sets a mammoth undertaking long after the final image has been taken.
an archive, which can be used by professional and amateur astronomers. “A lot of amateur astronomers use similar techniques with their own cameras and telescopes,” Read points out. “They’ll make dark and flat-field corrections and calibrate the data in the same way. We just do it on a global scale and, hopefully, to a higher level of detail.” But it’s not just for the benefit of professional astronomers. “We also provide material for citizenscience projects. Some of our images have gone into Galaxy Zoo,” he adds.
Mines of information The scale of the current projects can be astounding. The VISTA project, for example, sets out to catalogue the billions of objects in images of the galactic plane. “We’re now producing tables with tens of billions of rows, one for each object, which we’ve never done before.” Read explains. “We’ve many, many tens of columns of attributes – of stars’ positions, colours, magnitudes and so on – so that users can pick out a lot of the data. They can find all of the galaxies in a particular region of the sky or search the database for one object across the whole sky – for example, the most distant quasars. Either way, you can start out with a hundred million objects and narrow it down to a few hundred, and take observations from that.” Enabling this kind of data-mining – impossible without computer assistance – requires a certain > skyatnightmagazine.com 2014
ESA, ESA-AOES MEDIALAB, KA SOUTH AFRICA, THINKSTOCK X 3, ESA/MATTHEW W L SMITH
The Atacama Millimeter/submillimeter Array (ALMA) of radio telescopes (a partnership between North America, Europe and East Asia in cooperation with the Republic of Chile) began scientific observations in the latter half of 2011 and has been fully operational since March 2013. Given that the ‘low end’ of data products will contain about 1GB of raw data, it’s not
66 DATA FLOW AUGUST
M33 wide field
SOUTHERN GALACTIC CAP > amount of bespoke IT. “We’ve written a lot of ‘curation’ software that enters the data into the database in bulk,” Read adds. “We’ve had to overcome certain issues, such as finding the quickest way of getting the data into the database, bulk-loading information into the table, and then tuning all that to get the best performance.” The Gaia data processing system, for example, was engineered using the programming language Java, and runs on a Unix-based operating system. “One of the advantages of Java is that it’s crossplatform,” explains Hambly. “It’s very easy to deploy it on different platforms, and that’s one of the reasons it was chosen. We try and choose the best tool for the job when the job is being done.”
M. BLANTON AND THE SDSS-III COLLABORATION, THINKSTOCK
Access issues As with so much else in our world, accessing all this astronomical data is increasingly being done online. “It has reached the point now that people are talking about cloud solutions for storage, so that the data is easily accessible to anybody around the world,” explains Hambly. That said, although today’s data storage solutions are increasingly online systems there’s still a place for using offline backup, such as magnetic tapes. “There are some pretty good developments in tape technology that mean it’s still feasible to back up very large data sets and
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M33
NGC 604
NORTHERN GALACTIC CAP stick them on a shelf somewhere as a kind of insurance policy,” Hambly adds. “The actual missions to gather data, be they ground or space based, are extremely expensive. To go back and collect data again is often not an option, so we owe it to posterity – and to the taxpayers who ultimately cough up the money for the projects – to preserve the data.” Certainly retaining raw data avoids the risk of unknowingly throwing the baby out of an unexpected astronomical discovery with the bathwater of ‘background noise’ that can’t be deciphered at this particular time. Storage is, arguably, the foundation upon which the usefulness of such huge surveys rests; it enables us to retain, review and revisit the resulting data easily at any point in the future. That brings with it the potential of further extrapolation, as multiple data sets from around the world can be matched and linked as the means to do so becomes available. This systematic approach would enable new science, in addition to what can be done with individual surveys – perhaps leading to insights that could influence the design of future space missions. Perhaps more importantly, access to such vast amounts of data could allow scientists to conduct observational research without needing access to a ground-based telescope. S
Each orange dot in these Sloan Digital Sky Survey images represents a galaxy that can be zoomed in on
ABOUT THE WRITER Paul F Cockburn is a freelance journalist who has been writing about science and technology – past, present and future – since 1996.
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MIKKEL JUUL JENSEN/SCIENCE PHOTO LIBRARY, CORTESY OF BONHAMS X 5
COLLECTING THE
COSMOS As space memorabilia becomes increasingly valuable, Kieron Allen talks to three experts about the easiest way to start a collection and how to find the best items
G
one are the days when space memorabilia collectors were forced to scour the internet for hard-to-find items or travel to small, pop-up shows across the country in search of an elusive piece of
skyatnightmagazine.com 2014
space rock. Collecting space memorabilia has become a big business and there are more and more people vying for a slice of space history. Whether it’s through a world-class auction house or one of the many dedicated online shops, it’s never
been easier to start a collection or add to an existing one. We spoke to three experts who make a living from the space memorabilia industry to find out how they got started and what tips they have for budding collectors.
SPACE MEMORABILIA AUGUST 69
MATTHEW HAYLEY
þ Documents signed by astronauts sell well, but spacesuits fetch the highest prices
ROLE: Space memorabilia auctioneer TOP TIP: Start your collection by investing in a piece from the Apollo era. Small segments of heat shields of the re-entry craft mounted in acrylic sell for between $100 and $1,500 (approximately £60-£900). www.bonhams.com
MATTHEW HAYLEY WAS responsible for Bonhams’s inaugural space memorabilia sale, which took place in New York in 2008 to coincide with the 40th anniversary of NASA’s Apollo 11 mission. Today, he continues to play a major role in the auction house’s space memorabilia department. Hayley decided to hold the first sale after being approached by a client with a good stock of memorabilia who was also willing to offer his services as an expert. “After that first sale we received more and more enquiries thanks to the press coverage it generated,” he says. “That’s when we decided to make it a permanent category.” To date, Bonhams has run six space memorabilia auctions and Hayley has seen a rise in the number of collectors, “It’s interesting because there was a core of collectors already out there but a lot of people from our existing clientele have also started buying space memorabilia. They’re not new to Bonhams, but they are new to the space memorabilia field.” By far the most popular mission in terms of memorabilia has been Apollo 11, says Hayley. That’s quickly followed by Apollo 8 (the first to circle the Moon) and Apollo 15, which saw NASA’s lunar rover deployed for the first time. Sales of spacesuits have proved particularly successful. The most expensive item Hayley ever sold at
auction was a suit from the 1974 Apollo Soyuz test project. It went for a staggering $242,000 (£142,650). “People warm to spacesuits as they appeal to everyone’s Buzz Lightyear idea of a spaceman. They’re very approachable. But, models do well too,” he says. “We sell a lot of scale models that were made during the Apollo space programme by contractors, so they are official.” The Moon is another great draw for buyers and Bonhams has sold many items that have flown to Earth’s satellite, including flight plans and other items taken to the lunar surface. According to Hayley it doesn’t have to cost the Earth to purchase a piece of space memorabilia as an investment. “I think a good way of getting something that flew into space is by picking up a NASA-issue acrylic block containing segments of a heat shield from an Apollo re-entry craft. They can be had for about $1,000-$1,500 (£590-£885),” he says. “Provenance is very important in the space field,” he continues, “A lot of the stuff that we’ve sold has come from astronauts directly, or at least from their collections, and comes with a letter from them. That does add a fairly significant premium onto things.” If you’d like to enter a piece of your own into the next space auction, contact Matthew Hayley on
[email protected]. skyatnightmagazine.com 2014
70
ROBERT PEARLMAN
ROLE: Editor of www.collectSPACE.com TOP TIP: Be sure to specialise in a specific area of space memorabilia; this will make the hobby more enjoyable and easier to manage. www.collectSPACE.com
ROBERT PEARLMAN STARTED his website 15 years ago as a personal project. But through word of mouth, collectSPACE soon grew into an important online community for space history enthusiasts and collectors that now boasts 250,000 members and 4.3 million readers per month. “I’ve been interested in space since the age of six,” says Pearlman. But it wasn’t
until the early 1990s that I discovered there were collectors out there and I wrote to one of them. A gentleman call Ken Havekotte sent me a box containing all sorts of memorabilia – autographs, flown items, stamps and coins. Ken’s advice was to find what I liked in the box and specialise, so that’s what I did.” Pearlman specialises in space-flown material but he insists that whatever you choose to focus on should to reflect your own personal taste. “It really depends on the area you’re interested in; perhaps you’re more excited by engineering and hardware or maybe it’s the astronaut experience that matters to you,” he says. “Either way, there are ample opportunities to get involved so long as you’re patient – a collection isn’t a something you can build overnight.” A big part of collecting space memorabilia is understanding the history behind the pieces you own. But it’s impossible for any one person to
know everything there is to know about all aspects of space exploration, says Pearlman. That’s where the community he’s built through his website has helped. When Pearlman started collecting, the community was small and pieces from the Apollo programme could be picked up for a few hundred pounds. But as the collecting community has grown, so has demand, which has led to an increase in prices. “We have many more collectors from around the world who are perusing and pursuing space memorabilia, particularly in the UK,” he says. “It’s a hobby that’s driven by both current news and nostalgia. A lot of collectors got into it because they remember the Apollo astronauts landing on the Moon. At the other end of the spectrum are people like me who were born after the lunar landings. By holding on to pieces of material that have travelled to the Moon, we’re keeping those missions alive.” Any item that has touched down on the surface of the Moon and returned to Earth is a holy grail for space memorabilia collectors. But Pearlman says the easiest way to start a collection of space memorabilia is to send a letter to your favourite astronaut or cosmonaut. It will only cost you postage and there’s a good chance of receiving a reply from them with an autograph. If you’d like to start your collection this way Pearlman lists the addresses to contact on his website at www.collectspace. com/resources.
< Commemorative stamps of famous missions are another great way to start a space memorabilia collection skyatnightmagazine.com 2014
SPACE MEMORABILIA AUGUST 71
< Iron meteorites like those on the left make good collectors’ items, but for Bryant it’s the pallasites, like those shown below, that are the most beautiful
ROLE: Meteorite expert and Space Rocks dealer TOP TIP: Start soon! Demand for meteorites is outstripping supply as more countries bar the export of space rocks. www.spacerocksuk.com
DAVID BRYANT TAUGHT meteoritics for 35 years until his retirement. About 20 years ago he discovered that there were people like him that collected meteorites and by 1998 had set up a meteorite store, named Space Rocks. Although large meteorites can sell for thousands of pounds, Bryant decided
the best approach would be to purchase a chunk and break it up so that anyone who wanted to own a piece of the Moon or Mars could do so for a relatively small investment. Bryant began collecting space rocks at the age of eight. “My father liked to indulge my brother and I in all things astronomy. We were down at Herstmonceux once and I found a little piece of black stone lying in a small crater. I was convinced it was a meteorite and so my dad suggested I write to Patrick Moore.” Moore invited Bryant and his father to his home to inspect the rock. Although it turned out the rock wasn’t a meteorite, Bryant continued correspondence with Moore for many years. There are different types of meteorites to collect, but some of the rarest are the achondrites. “These tend to originate from the planets,” says Bryant. “Then there are the really rare achondrites like angrites, some of which may come from Mercury. There’s a lot of interest in those at the moment.” Bryant also rates black diamonds (Carbonados), which originate from central Africa and South America. Their origin is unknown. Some believe they formed on Earth; others that they formed during supernovae. The latest research suggests that they might have orginated from impacts on the outer gas giants.
Bryant thinks the most beautiful of all are pallasites. They are thought to be from the core-mantle boundary of a disrupted planet and consist of a silver matrix with yellow, green and orange olivine crystals suspended inside. Bryant saw demand for his meteorites explode in the wake of the Chelyabinsk meteor event. “I was able to get 200-300 Chelyabinsk fragments and the demand for them is astronomical,” he says. But his business can be self limiting, with demand quickly outstripping supply as a lot of countries are restricting, or even barring, the export of meteorites. For new starters Bryant suggests investing in a Campo del Cielo meteorite, as they’re undervalued. “They’re beautiful, heavy pewter meteorites. Something with a mass of 1-2kg would cost about £150. They’re instantly impressive to anybody. “Meteorite prices are going up all the time, but a stable pallasite would be a superb investment as they’ve probably doubled in value over the past year.” S ABOUT THE WRITER Kieron Allen is Sky at Night Magazine’s online editor. He became a science writer in 2011 after gaining a postgraduate diploma in journalism.
skyatnightmagazine.com 2014
ROBERT PEARLMAN, THINKSTOCK X 5, DAVID BRYANT X 3
DAVID BRYANT
OBSERVING PERSEID METEORS BY RADIO Tune in to the right frequency and you’ll be able to hear the Perseids as they fly through the sky, writes Vincent S Foster ABOUT THE WRITER Vincent S Foster has been an amateur astronomer for over 50 years. He chairs the Hydrogen-Alpha Solar and Bright Nebula observing programmes for the Astronomical League.
74
Þ Catching the Perseid meteor shower might be best done by radio this year as a bright gibbous moon will blot out many of the trails
T
he Perseid meteor shower is likely to be spoiled this year by light from a waning gibbous Moon. But all is not lost: it’s easy to track the meteors by listening to them on your FM radio at home or in your car. Meteors burn up in the atmosphere and leave an ionised trail, which acts like a mirror to reflect transmitted signals from FM radio stations hundreds of kilometres away. You can find one on these stations by looking for big cities far enough from you and then searching online for a suitable radio station transmitting from there. All meteors can be detected like this, and it’s because radio can detect smaller particles than can be picked up by visual observations. The human eye can only see shooting stars brighter than sixth magnitude, but radio can detect meteors that are at least five times dimmer. This
simple way of observing can also be employed during daylight hours.
Sight versus sound The one serious drawback to observing meteors by radio is that you can’t tell what direction they came from. Visual observers can easily tell if it was a Perseid
using an amateur radio set at a known TV or radar frequency. This method requires an amateur radio with a dipole antenna. It allows you to hear or record pings of varying intensities and lengths amid background static. If a setup like this is beyond your scope, you can hear a live broadcast of them on the internet. Just connect to Spaceweather Radio at www.spaceweather radio.com. While the number of signals you hear will depend on what equipment you have, the advantage of listening to meteors is that you can hear ones that are too faint to see. With the naked eye you can see the arrival of a particle as small as 1/100th of a gram on a dark night, but dust grains much smaller than this can be detected using radio observation. In order to do so, however, you have to approach meteor showers differently, as you’ll need to know the date of peak
THINKSTOCK X 2, PAUL HYDE
“Radio can detect smaller particles than can be picked up by visual observations”
skyatnightmagazine.com 2014
meteor emanating from a radiant in Perseus or if it was a sporadic meteor that came from somewhere else. Radio listeners can’t. But radio observation is something you can do when visual conditions aren’t good. So the best approach is to use your radio on cloudy nights and use your eyes when the sky’s clear. You can also make radio observations of summer’s standout meteor shower
RADIO OBSERVATION AUGUST 75
Spaceweather Radio will broadcast the sounds made by the Perseid meteors
in bright meteors, it also occurs during summer in the northern hemisphere, whereas other similarly productive meteor showers, such as the Geminids, take place in the cold nights of December.
When to watch
We showed you how to construct a dipole antenna in the How to section of our June issue
activity – you can do so online on the International Meteor Organization’s website at at www.imo.net. There are also daytime meteor showers that can be observed only by radio because the radiant is close to the Sun. Among
them are the Arietids, which lasts from late May until early July each year and peaks on 8 June. Arietid meteors stream out of the constellation Aries. Their source is unknown, but some astronomers suspect they come from the sungrazing asteroid Icarus, the meteoroids hitting Earth’s atmosphere with a velocity of 39km/s. Another annual daytime meteor shower around the same time is the Zeta Perseids, which occurs between 20 May and 5 July. Maximum rates are on 9 June. This meteor shower is one of the strongest of the year, with a maximum rate of 50-80 per hour. The Beta Taurids is a third daylight shower, which is active between 5 June and 17 July. It exhibits a relatively flat maximum each year around 28 June. Beta Taurid meteors come from the same meteoroid stream as the Taurids. Despite not producing peak rates as high as those of the Geminids, the Perseid meteor shower remains the favourite for many. Besides being rich
< Any device can listen in on meteors as long as it can pick up an FM signal
The highest observed rates on any given night are likely to be seen when the radiant is highest in the sky late at night. In some years, when the Earth encounters dust trails from old returns of the Perseids’ parent comet 109P/Swift-Tuttle, there can be more than one Perseid peak. However, there are no predictions for additional Perseid peaks in 2014. Visual observing conditions will be good for the early Perseids between 26 July (when there will be a New Moon) and 4 August (when there will be a First Quarter Moon). However, conditions will then become unfavourable with a full Moon occurring on 10 August, which is near the Perseids maximum. The Perseids peak on the night of 13/14 August for UK observers, when there will be a 92 per cent illuminated waning gibbous Moon. On the night of maximum, the Moon will have already risen before twilight ends and will be present throughout any meteor watches. Radio observations are better overnight when human activity is low. Also, the number of detectable meteors increases after midnight when Earth’s leading edge travels into the stream of sporadic or shower meteors. These meteors tend to enter the atmosphere at a greater speed because of Earth’s velocity through space of 29.8km/s. This higher energy translates into higher levels of ionisation. As a result, many radio meteor observers conduct their observations between midnight and 7am. S Turn the page for a step by step guide to finding and listening to meteors on a radio
X
skyatnightmagazine.com 2014
76 RADIO OBSERVATION AUGUST
STEP-BY-STEP GUIDE How to find an FM station that will allow you to listen to meteors on your radio
STEP 1 You could listen to the sounds made by Perseid meteors by visiting www.spaceweatherradio.com, but it’s much more fun (and rewarding) to catch the reflected radio waves yourself. First, make a note of the frequency of each station your FM radio is able to pick up as you adjust its tuner from the lowest setting to the highest one.
STEP 2 You need to find an FM radio station that doesn’t broadcast on any frequencies on which you can already pick up radio stations – in other words, you need to identify a radio station that you can’t hear from your location. We’ll explain how to do this in the next three steps.
STEP 3 In order to get optimum results you need to find an FM radio station that is approximately 1,300km away from your location. This usually gives the longest-duration signal, thus increasing your chances of picking up the crackles of the radio waves reflected off the trails of meteors passing through Earth’s atmosphere.
STEP 4 To find a suitable radio station use a compass centred on your location to draw three circles on a map, one at 200km, another at 1,300km and a third at 2,100km. Find an FM radio station that transmits on a frequency different from the ones you can hear on your FM radio from somewhere between the smallest and largest circles.
THINKSTOCK X 2, WIKIPEDIA
…AVEC UNE… …JE SUIS…
STEP 5 Though not 1,300km away, you could use a suitable radio station located within the UK – a list can be found on Wikipedia. You want the one with the highest broadcast power, which is measured in kilowatts – this will reveal meteors with the longest duration. You can check the power of all UK and Ireland FM transmitters at www. frequencyfinder.org.uk/FM_Stations.pdf.
skyatnightmagazine.com 2014
STEP 6 You’ll hear meteors as brief bursts of speech or music. As the meteors arrive, you might also hear pops and whistles. It is best to observe after midnight – and not only because human activity is at its lowest. After this time, Earth’s rotation puts us on the leading edge of our planet’s orbital path through space, meaning that more ‘slow’ meteoroids enter our atmosphere, while faster ones leave brighter trails.
SKILLS
Brush up on your astronomy prowess with our team of experts
78 81 85 87
THE GUIDE HOW TO SKETCHING SCOPE DOCTOR
The Guide Meteor observing basics With Ade Ashford
Meteor hunting is a simple, rewarding affair – here’s how to get started
DO I NEED BINOCULARS? Meteor observing can be rewarding using nothing more than the naked eye, but it is possible to use binoculars to detect meteors far fainter than you can see with your eyes alone and that are far more plentiful close to the radiant. You should use low-power binoculars to give a large field of view – so 7x50 or 8x40 models are preferable, since they also gather lots of light. If you have some sort of mount to relieve the strain of holding them, so much the better.
The large field of view of 7x50 binoculars make them great for meteor hunting
There are many spectacular showers throughout the year – these are the Leonids, which occur in November
T
he dramatic flash of a fireball slashing the sky is an event guaranteed to please both casual and experienced observers alike. While most meteors will be less imposing, observing a large number of them during the peak of a major shower skyatnightmagazine.com 2014
is a great way to spend a pleasant summer evening. Here we reveal some top tips that will help you get the most out of any meteor shower, and with the Perseids peaking this month on 12-13 August you’ve plenty of opportunity to put them into practice.
The first thing to consider is where you are going to watch a meteor shower from. If you happen to live in a lightpolluted area you can vastly improve your observing experience by travelling out of town to a more remote location, but be mindful of your personal safety. As with any form of observing it’s important to be comfortable, but meteorwatching vigils in particular often require you to stay still for long periods. Your best bet is to scour the sky from the comfort of a sunlounger or garden recliner. Since you’ll be sitting for long periods it’s very important to keep warm, so wear a hat to prevent heat loss from the head and by all means snuggle into a sleeping bag. In the
THE GUIDE AUGUST 79
Under perfect conditions, the Perseids can deliver an average of one meteor a minute at peak
PEAK PROBLEMS
Meteoroids from the same source tend to travel through space in parallel paths, so the effect of perspective means that their tracks through the atmosphere appear to converge on a radiant situated in the constellation that gives the shower its name. The best time to observe is shortly after midnight on the date of the predicted maximum, when the sky is darkest and
There is also the chance that Earth could encounter an unpredicted dense swarm of meteoroids along the path of debris in the wake of a shower’s parent comet; the dynamics of all showers are not fully understood and surprises can occur.
sensitivity in darkness. If you need to refer to star charts or books to find the radiant, it’s best to use a dim red light rather than a white one so that you preserve your dark adaptation; if you use a smartphone app for this purpose, place a red cellophane filter over the screen. There’s always a risk that you’ll miss the best fireball of the night while taking notes, so if you wish to jot down your observations it’s far better to use a tape or digital recorder – that way you can keep your eyes on the sky. Try to record the time, start and end points of the track and estimate the brightness of prominent meteors. While conditions are not ideal for the Perseids this year – the Moon will interfere – it’s not the only natural firework display, with the Orionids (peak 21 October) Leonids (peak 17 November) and Geminids (peak 14 December) among those still to come in 2014. S Ade Ashford is an astronomer and science journalist skyatnightmagazine.com 2014
ALAMY, ROGER HARRIS/SCIENCE PHOTO LIBRARY
Earth’s rotation faces into the direction of the planet’s motion in space, giving additional swiftness to oncoming meteors. Don’t look directly at the radiant, but concentrate your gaze high in the direction of the darkest portion of the sky that’s free from obscuring trees and buildings. If you’re observing in company, try to view different parts of the sky to each other so you catch as many meteors as possible. On occasions when the Moon is unavoidably in the sky, try to ensure that it’s not in your field of vision or reflecting off nearby walls or windows, as this will seriously degrade your night vision. As with any Meteors are often seen after other form of observing, midnight, when Earth rotates us your eyes need at least 20 head-on into its orbital motion minutes to reach peak
summer months you may also need to consider insect repellent. Bring along some food and a vacuum flask of your favourite hot beverage to drink at regular intervals – hydration is important, plus a little caffeine will certainly keep you alert.
When and how
should always be vigilant during the week of the shower, spreading your observing opportunities to bolster the chance of success. Prominent displays such as the Perseids at their peak can produce an average of one meteor a minute under clear, moonless skies.
DR FRED ESPENAK/SCIENCE PHOTO LIBRARY, PAUL WHITFIELD,
While peaks are important to bear in mind, most major showers will be active over a period of at least a few days so you should not restrict your observing just to the dates of the predicted maxima. The vagaries of cloud cover and moonlight mean that you
SKILLS
HOW TO AUGUST 81
How to Flock a Newtonian telescope With Steve Richards
Blot out unwanted reflections with this straightforward project
TOOLS AND MATERIALS
CRAFT KNIFE AND CUTTING BOARD
A sharp craft knife and cutting board are needed for trimming the flocking material to the correct size. FLOCKING MATERIAL
Black self-adhesive film is available from Hobbycraft or Wilkinsons at a cost of about £7 per roll. METAL STRAIGHT EDGE
A steel rule will make it easy to cut a fine accurate edge. Lining the inside of your scope with a black material can help you to get better contrast views
ALL PICTURES: STEVE RICHARDS
O
ne of the problems associated with Newtonian reflectors is the reduced contrast of the view in comparison with a refractor. There are various causes of this, including the central obstruction created by the secondary mirror, but there is not much you can do about that. However, another contrast-zapping issue – the reflection of stray light – can be tackled head on. It is this aspect of contrast improvement that is the subject of this How to. The open-ended design and relatively large apertures associated with Newtonian reflectors make them a magnet for stray light entering the optical tube, where it can be reflected into the eyepiece. The result of this extraneous light is wishy-washy backgrounds and reduced contrast. Adding a long dew shield to the front of the telescope to prevent stray light from
reaching the inside of the tube in the first place can lead to an improvement, but there are other areas where reflections can be a nuisance. All manufacturers make some attempt at removing stray reflections by painting the inside of the tube with matt black paint. Although this is helpful, it doesn’t always resolve the issue effectively, as even matt black paint is reflective to some extent and the quality of the paint’s application can be variable. High-end instruments are designed with baffles placed at strategic intervals down the inside of the tube to absorb unwanted light and these can be very effective indeed, but are probably beyond the DIY skills of most amateur astronomers. Lining the inside of the telescope tube with black flocking material, on the other hand, is a simple and very effective way of killing unwanted reflections, as the
SCREWDRIVERS
A medium-sized crosshead screwdriver and a spanner will be required to remove the focuser and the primary and secondary mirror cells. TAPE MEASURE AND PENCIL
You will need to accurately measure the flocking material and mark it for cutting.
light is simply absorbed by the relatively ‘rough’ and very black surface. To give an idea of the main areas that should be covered with the flocking material as an absolute minimum, remove the eyepiece and tube dust cover and look through the focus tube. Every surface that you can see (with the exception of the mirrors!) should be covered with flocking material as they are all likely sources of unwanted light. In reality, it makes most sense to cover as much of the inside of the tube as possible. > skyatnightmagazine.com 2014
SKILLS STEP-BY-STEP GUIDE
Measuring up carefully is essential to make sure you cover the most important areas > The black velour flocking material we use is available in 45x100cm sheets bought in roll form; take care to choose packs that have not been dented. You’ll need to calculate the amount of flocking material required for your own particular scope; for this purpose, you should assume that you will be flocking the whole of the inside of your optical tube. The total amount of material required can be ascertained by determining the circumference of the tube then measuring the tube length.
STEP 1
STEP 2
Start by disassembling the telescope. Place pieces of masking tape on the tube and baseplate so that you can return them to the same position later. Loosen the small screws that retain the base of the telescope and remove the whole of the primary mirror cell.
Gently hold the secondary mirror assembly through the spider vanes. Remove the central retaining screw from the vanes and withdraw the mirror. The spider vanes can then be taken out using the knurled knobs that normally hold them to the edge of the optical tube.
STEP 3
STEP 4
Leaving the front ring that supports the spider vane in place to give the tube some stability, remove the focuser assembly – using either a crosshead screwdriver or Allen key as appropriate and a small spanner to hold the nuts still. Now remove the finderscope base.
Cut the first length of flocking material, allowing a 5mm overlap for the internal circumference. Starting at the front, peel off about 10cm of the backing sheet and gently apply the flocking material to the inside of the tube, smoothing it out and unrolling it as you go.
STEP 5
STEP 6
Apply the rest of the material from the bottom end butting up to the edge of the first piece if you have enough. Using the craft knife, carefully cut out holes for the focus tube and mounting bolts. Re-install the finderscope bracket and focuser assembly.
Assemble the rest of the components in reverse order, being very careful not to touch any of the mirror surfaces and ensuring that the masking tape markers line up accurately. Finally, carry out a full collimation of the telescope using a Cheshire eyepiece.
ALL PICTURES: STEVE RICHARDS
Covering all the gaps The tube circumference is simply found by multiplying your telescope’s physical aperture (the diameter of its tube) by . For example, our 10-inch Newtonian reflector has an actual tube diameter of 28.8cm, so the circumference will be 28.8 3.14, which equals 90.5cm; the length of the tube is 107.0cm. In this example, we’d recommend that you cut the material for the circumference from the 100cm length (allowing for a 5mm overlap). A total of three sheets would be required to completely cover the inside of the tube. Alternatively, you could use just two sheets and leave a small gap of 17cm in the centre of the optical tube – where there will be the minimum risk of reflections – and partially fill this area using the off-cuts from the two main pieces. This inexpensive and simple procedure will have a marked effect on the quality of your views through the eyepiece and will result in higher contrast images too. If you are feeling brave, you could also paint the edge of the secondary mirror matt black, as this too can contribute to stray light. However, only consider doing this if you are absolutely sure that you can perform the work without getting any paint on the surface of the mirror. S Steve Richards is a keen astro imager and an astronomy equipment expert skyatnightmagazine.com 2014
SKILLS
SKETCHING AUGUST 85
Sketching Kemble’s Cascade With Carol Lakomiak
NEED TO KNOW NAME: Kemble’s Cascade TYPE OF OBJECT: Asterism STEP 1 With a 2B pencil, draw the brightest stars in the field. Begin with the centre star and then determine the placement of the others. These are your ‘anchor’ stars and will be the foundation of your sketch, so it’s important to place them as accurately as possible.
CONSTELLATION: Camelopardalis RA: 03h 57m (centre of asterism) DEC: +62° 52’ (centre of asterism) EQUIPMENT: Binoculars or wide-field telescope; 2B and HB pencils; blending stump BEST TIME TO SKETCH: 20-31 August, 23:00-03:00 BST (22:00-02:00 UT) FIELD OF VIEW SHOWN: 180 arcminutes; 15x magnification
ALL PICTURES: CAROL LAKOMIAK
T
his month’s asterism is named after Father Lucian Kemble (1922-99), a Franciscan monk and amateur astronomer from Alberta, Canada. While scanning the sky with his 7x35 binoculars he ran across “a beautiful cascade of faint stars” near Cassiopeia, and notified Walter Scott Houston of his find; (Houston was the author of Sky and Telescope’s Deep-Sky Wonders column from 1946 to 1994). When Houston wrote about the asterism in a 1980 issue, he called it Kemble’s Cascade, thus creating the familiar moniker. To find this chain of stars, first locate Beta and Epsilon Cassiopeiae; they’re the outer tips of the constellation’s W shape. Then imagine a line spanning the 13º between the two stars, and extend the line another 13º past Epsilon. Kemble’s Cascade is a fairly large object and is best seen through binoculars or a telescope that can show at least a 3° field of view. As an added bonus, open cluster NGC 1502 is at one end of the cascade. Step 1’s anchor stars range in brightness from mag. +4.8 to mag. +7.4. A good place to begin your sketch is with the mag. +5.0 star at the centre of the
asterism. Begin with the centre anchor star and work outwards into the two adjoining triangles. From there, simply determine the placement of the other anchor stars based on their relation to the ones you’ve already drawn. You’ll notice that three of the anchor stars are near the edge of the field of view. They’ll be helpful as ‘framing stars’ if your telescope doesn’t have tracking. As the Earth rotates on its axis, stars seen through a non-tracking telescope slowly drift out of the field. To make sure your eyepiece view always matches what’s in your sketch, adjust your telescope so the framing stars are in the same location in the eyepiece as they are in your sketch. Draw the cascade and then populate the star field – be sure to draw dimmer stars smaller and lighter than the brighter ones. Open cluster NGC 1502 will probably appear as a small glowing patch – you can create an accurate representation of it with a blending stump). Do also include any other individual stars that you are able to resolve. Carol Lakomiak is BBC Sky at Night Magazine’s sketching expert
STEP 2 To draw the cascade, use an HB pencil and begin at the asterism’s centre star. Draw the northwest portion first, then the southeast part. Add in NGC 1502 by lightly coating the tip of a blending stump with HB graphite and making small circular motions.
STEP 3 Populate the star field with an HB pencil. As you draw the gradually fainter stars, use less pressure on the pencil and make the stars progressively smaller. Triangulate the location of the other stars or notice any familiar shapes they form to help you to draw them accurately.
skyatnightmagazine.com 2014
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SKILLS
SCOPE DOCTOR AUGUST 87
Scope
With Steve Richards
DOCTOR
Our resident equipment specialist cures your optical ailments and technical maladies
Manually finding targets is a great way to learn how to navigate the night sky
STEVE’S TOP TIP
attempts What are good targets for my first at astrophotography? target for The Moon makes an excellent first use it is beca learning to focus manually and, t exposures shor very take bright, you only need to Then il. deta fine ul derf to capture some won lenging you can move on to some more chal deep-sky objects. to capture As it happens, August is a great time can you – Way y Milk the of e a wide-field imag an and lens era cam dard stan a g do this usin 120 seconds. exposure time of between 30 and telescope, a on nted With your camera mou de globular inclu ld wou cts obje suitable first time glorious the by wed follo , M92 and clusters M13 0. North America Nebula, NGC 700
Your website recommends Newtonian telescopes for beginners. Do you have any recommendations? I was wondering whether a Celestron AstroMaster 130 EQ-MD was a good option? STEVE CHAPPELL
PAUL WHITFIELD X 2
What’s the best way to line up a manual equatorial mount and centre objects for quick observations? RICHARD DALLAWAY Many observational astronomers prefer to use a manual mount rather than a Go-To and it’s a great way to learn your way around the night sky. Set up your telescope during daylight and centre a distant object such as a pylon or church spire in your shortest focal length eyepiece, then align your finderscope to the same object. Carry out a basic polar alignment, using a compass to point the mount’s polar axis to true north and adjusting the mount’s elevation until the latitude scale matches that of your location. Alternatively, adjust the mount in azimuth and altitude so that Polaris is visible through the hole bored through the polar axis, if there is one.
Now, using a star chart or your preferred planetarium software, choose a bright star that you recognise, is reasonably close to the object you wish to observe and has the same declination (dec). Locate the star with your finder, then use a high magnification eyepiece to centre the star through the telescope. Adjust the right ascension (RA) and dec setting circles to match this star’s coordinates as closely as you can. Rotate the RA axis until the RA setting circle matches the RA of your chosen object. Swap the eyepiece for a lower magnification one and sweep the area back and forth in RA until you spot your intended target.
Newtonian reflectors represent particularly good value for money as they are much cheaper than equivalent aperture refractors. For observing, aperture size is very important: the larger it is the brighter the view, allowing you to see dimmer objects. The Celestron Astromaster 130EQ-MD is an excellent beginner’s telescope with a reasonable aperture of 5 inches and a driven equatorial Dobsonians – which are mount. It’s a pretty good also reflectors – make all rounder for both Solar good beginner scopes System and deep-sky observing, although the planets will seem quite small. A very popular alternative to an equatorial mount is the more robust but undriven Dobsonian mount. If you felt like stretching your budget to just over £200, you could afford a 6-inch aperture reflector such as the Sky-Watcher Skyliner 150P, which has approximately 33 per cent greater light grasp. Its 1,200mm focal length would make it more suitable for Solar System observing as well. Steve Richards is a keen astro imager and an astronomy equipment expert
Email your queries to
[email protected] skyatnightmagazine.com 2014
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REVIEWS AUGUST 89
Reviews Bringing you the best in equipment and accessories each month, as reviewed by our team of astro experts
HOW WE RATE Each category is given a mark out of five stars according to how well it performs. The ratings are:
+++++Outstanding +++++Very good +++++Good +++++Average +++++Poor/Avoid
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We find out whether this wide-field eyepiece can deliver the ‘wow’ factor
SEE INTERACTIVE 360° MODELS OF ALL OUR FIRST LIGHT REVIEWS AT WWW.SKYATNIGHTMAGAZINE.COM
WWW.THESECRETSTUDIO.NET X 5
This month’s reviews
First light
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Sky-Watcher Heritage 100P Tabletop Dobsonian
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Altair Lightwave Hyperwide 100º eyepiece
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AstroHutech Hinode SG solar autoguider
Books
Gear
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We rate four of the latest astronomy titles
Including this set of guidescope rings
Find out more about how we review equipment at www.skyatnightmagazine.com/scoring-categories skyatnightmagazine.com 2014
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See an interactive 360° model of this scope at www.skyatnightmagazine.com/sw100p
Sky-Watcher Heritage 100P
Tabletop Dobsonian This tripod-less telescope is perfect for on-the-fly observing WORDS: PAUL MONEY
ALL PHOTOS: WWW.THESECRETSTUDIO.NET
VITAL STATS • Price £99.99 • Optics Parabolic mirror • Aperture 100mm (4-inch) • Focal length: 400mm (f/4) • Mount Wooden altaz • Extras Two 1.25-inch eyepieces (25mm and 10mm), 2x Barlow lens, red-dot finder • Weight 2.8kg • Supplier Optical Vision • www.opticalvision. co.uk • Tel 01359 244200
SKY SAYS… The Heritage 100P can provide rewarding views as long as you have realistic expectations
D
obsonian telescopes tend to occupy the larger end of the aperture scale, but it’s interesting to note that the same design philosophy has also extended in the other direction as well. The Heritage 100P is one such example: it’s a 4-inch tabletop Dobsonian from Sky-Watcher that costs just under £100. The Heritage 100P looks stylish. Its 4-inch parabolic mirror has a focal length of 400mm, giving a focal ratio of just f/4. It comes packaged with two 1.25-inch eyepieces (25mm and 10mm), a 2x Barlow lens and a red-dot finder. Installation is easy: attach the finder, pop in an eyepiece, and you can be viewing the heavens in moments. As the name suggests, the Heritage 100P Tabletop is a telescope that’s been designed to sit on top of something else – a garden table or any other flat, medium-height surface will suffice. Indeed, we could sit down in comfort and view most of the sky when we used it on the patio table. The focuser is a basic rack and pinion type; it was a little stiff, but still gave good control. The finder is zero magnification, with its small red dot projected onto a clear screen, and we found it very easy to align with the main telescope. One quibble with the focuser and finder is that their positioning feels wrong when it comes to using the telescope. We found the finder sometimes seemed to be in the way when we looked through the eyepiece; if their
positions on the tube were swapped, it would improve the ease of use. The mount gave good support and was smooth to use.
Accommodating field of view To check the quality of the optics, we first aimed the Heritage 100P at Regulus in Leo. Through the 25mm eyepiece the star remained a pin point for the central 60 per cent of the view, but beyond that it quickly deteriorated and showed signs of coma. Overall, the wide field views were not too bad; a fact confirmed when we turned to the galaxy pair of M81 and M82 in the Ursa Major. Swapping in the 10mm eyepiece gave us a better view of M82’s edge-on aspect, we could even make out some mottled structure along it. The constellation of Lyra was well above the horizon, so we aimed at the Harp’s two lower stars, Beta and Gamma Lyrae. They fitted comfortably within the view of the 25mm eyepiece, and even at its low 16x magnification we could just make out the Ring Nebula, M57, as a small spot between them. Using the 10mm eyepiece and the 2x Barlow lens, that small spot became a satisfying oval smudge. Elsewhere in the sky, we had to look at M13, the northern hemisphere’s showcase globular: the >
NO FUSS EXPLORING If a telescope proves too difficult to set up or use then there’s every chance that it will fall into disuse – it may even put its owner off exploring the night sky. So, by being compact, lightweight (2.8kg) and quick to put into action, the Heritage 100P could easily help to kickstart a lifelong interest in the Universe around us. Despite its small size it still gave decent views of a range of celestial wonders. We found it was easy to store and bring out quickly whenever the clouds cleared. Moreover, the Heritage 100P’s simple design allows it to be placed on a patio table or similar flat surface for that quick view, making it ideal to show off the brightest night-sky objects at social events. It would also make an ideal first telescope for a budding young astronomer.
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FINDER A red-dot finder is a reasonable choice for a telescope of this size as it is simple to use and quite lightweight. However, it felt as if it was in the way when using the focuser, and when the telescope was pointed vertically it was not easy to look up through the finder.
EYEPIECES Two basic eyepieces are packaged with the Heritage 100P, one 25mm giving 16x magnification, the other 10mm giving 40x magnification. The 25mm eyepiece was adequate but did not provide a sharp view across the whole field, but its 10mm counterpart gave pleasing views. A 2x Barlow lens is also supplied.
MOUNT The wooden, single arm altaz mount gave good free movement in azimuth. Altitude axis movement is smooth in use, and tension can be adjusted by a chunky knob at the side. The telescope is attached to the mount with a Vixen-style bar and can be removed if needed.
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FOCUSER The focuser is a basic rack and pinion style and takes 1.25-inch eyepieces. It was a little stiff but reasonably smooth to use. The focuser’s position on the telescope body did seem a little awkward and would have been better swapped with the position of the finder.
SKY SAYS… Now add these: 1. Red LED torch 2. 1.25-inch light pollution filter
OPTICS The 4-inch parabolic mirror has a relatively fast focal length of 400mm, giving the system a focal ratio of f/4. The optics performed reasonably well for their size and provided pleasing views of lunar, planetary and brighter deep-sky targets.
> wide-field view offered 3. Lunar/planetary by the 25mm eyepiece was pleasant, but the filter set increased magnification offered by the 10mm eyepiece plus Barlow lens allowed us to see a sprinkling of stars. Binary star Albireo showed wonderfully contrasting colours, especially through the 10mm eyepiece. We then turned to the major bodies of the Solar System. Jupiter was small even with the 10mm eyepiece, but we could see the equatorial bands and the four Galilean moons. Mars surprised us: the Dobsonian revealed a polar cap and dusky markings on the planet’s small disc. Saturn and its rings were a delight, with Titan and Rhea also visible and we were able to see plenty of craters on our Moon, although not in great detail. The Heritage 100P is a small, simple scope but it can provide rewarding views as long as you have realistic expectations. S
ASSEMBLY BUILD & DESIGN EASE OF USE FEATURES OPTICS OVERALL
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WWW.THESECRETSTUDIO.NET
VERDICT
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FIRST light Altair Lightwave Hyperwide See an interactive 360° model of this camera at www.skyatnightmagazine.com/al100
100° eyepiece A substantial eyepeice that offers impressive wide-field views
WORDS: STEVE RICHARDS
ALL PHOTOS: WWW.THESECRETSTUDIO.NET
VITAL STATS • Price £339 • Focal length 20mm • Apparent field of view 100° • Eye relief 14.5mm • Optics Nine, multicoated and edge blackened • Barrel size 2-inch • Extras Dust caps • Weight 879g • Supplier Altair Astro • www.altairastro.com • Tel 01263 731505
F
SKY SAYS…
or many years, the Plössl shorter focal length eyepieces result in The ability to see higher magnification. With common eyepiece has been the one most commonly shipped good lunar detail eyepiece focal lengths ranging from with telescope packages. 5mm to 28mm, the 20mm Hyperwide yet still view the Eyepieces of this type typically offer delivers views at the low magnification whole Moon a 50-52° apparent field of view, but end of the scale. produced a real more recently those offering wider Lower magnifications result in ‘wow’ moment views have become more popular. The wider true fields of view with a given substantially built Altair Lightwave telescope, making these eyepieces 20mm Hyperwide 100º eyepiece is the most suitable for large objects such as latest to follow this design philosophy. A large nebulae. Higher magnifications deliver narrower apparent field of view is appealing because it true fields of view and are at their best observing allows the same large expanse of sky visible through smaller objects such as planets or fine detail on a low-power eyepiece to be seen through one with the surface of the Moon. much higher magnification. The primary function of any eyepiece is to magnify the image produced by a telescope’s The ideal eyepiece be should unobtrusive in use, so optics, thus enabling you to observe celestial objects that you can concentrate on the view unencumbered in all their splendour. There are various attributes by distractions such as the circular black edge of the that must be borne in mind in the design of an field of view. The Hyperwide certainly removed this eyepiece, but the magnification obtained with a diversion with its wide apparent field. given telescope is the one that astronomers Another attribute that should be considered often consider first. The magnification of a when selecting an eyepiece is the eye relief, the given telescope and eyepiece combination distance between the outermost lens surface and is simply calculated by dividing the the position your eye needs to be for the best view. focal length of the telescope by the The eye relief of an eyepiece is independent of the focal length of the eyepiece. Thus, telescope it is used with. >
Ideals and practicalities
A MORE NATURAL OBSERVING EXPERIENCE The apparent field of view of an eyepiece describes the total angle of movement that your eye makes when traversing from one edge of the field to the other. The average adult has a maximum peripheral field of view of around 170° including actual eye movement, which is why it is possible to see the sharply defined edges of the field through an eyepiece, leading to the impression of observing through a porthole or tube. Increasing the apparent field of view diminishes this effect, producing a
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more natural and immersive observing experience that, taken to extreme, can make you feel as though you are floating in space. The complex design of the Hyperwide eyepece comprises nine multicoated and edge-blackened glass elements, resulting in an apparent field of view of 100°, which even by modern standards is pretty wide. This makes for pleasant and relaxed observing, with your eye able to cover a larger expanse of magnified sky in comparison with a conventional eyepiece design.
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2-INCH FILTER THREAD Many objects can be seen much better with the use of external filters, such as ultra-high contrast or narrowband OIII. Usefully, the Hyperwide’s barrel is threaded to take the larger 2-inch filters that are readily available, ensuring that the extra wide field of view is not compromised.
FOLD-UP RUBBER EYE CUP TAPERED 2-INCH BARREL Dropping such a substantial eyepiece would be an absolute disaster, so making sure it doesn’t slip out of its eyepiece holder is of paramount importance. This need is met by the 2-inch barrel, which has a tapered section close to the main body – adding a second line of defence should the retaining bolt become loose.
To obtain the best views from any eyepiece, stray light needs to be kept at bay. The fold-up rubber eye cup does an excellent job of surrounding your eye with a soft protective screen, but also provides a comfortable resting point for positioning your eye accurately over the exit pupil.
EDGE-BLACKENED LENSES Another of the various measures that improve the view through any eyepiece is increasing the contrast by preventing reflections. The blackened edges of the lens elements, together with high-quality anti-reflection coatings, do this very well indeed.
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RUBBER GRIP Handling any eyepiece outside in the dark (not to mention cold) requires great care. The Hyperwide has a very chunky 44mm-wide rubber grip, reminiscent of an off-road tyre, surrounding the widest part of the body.
by observing the Moon at first quarter, and were rewarded with an excellent view that was free of colour fringing. The ability to see good lunar detail yet still view the whole Moon in its natural surroundings produced a real ‘wow’ moment. We really enjoyed our observing time with the Hyperwide eyepiece and would recommend it to deep-sky observers looking for a more immersive view than normal. S
VERDICT BUILD & DESIGN EASE OF USE EXTRAS EYE RELIEF OPTICS OVERALL
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SKY SAYS… Now add these:
1. Altair 2-inch quartz dielectric diagonal 2. Kendrick 2-inch eyepiece dew heater 3. Kendrick dew controller
WWW.THESECRETSTUDIO.NET
> A distance of 15-20mm is ideal, with a greater distance making it easier to use if you wear glasses. The Hyperwide has an eye relief of 14.5mm, making it a little tight for such stargazers, but fine for everyone else. We tested the eyepiece on all sorts of celestial objects, starting with the Andromeda Galaxy, M31, which looked spectacular through our 4-inch apo refractor. With the summer Milky Way cartwheeling into view, we meandered our way towards it – taking in globular clusters M3, M13 and M92 en route, all of which stood out crisply. Visiting the bright star Vega in Lyra showed that there was a small amount of astigmatism present, and a small ghost reflection was just visible when the star was moved off-axis. Generally, star shapes were good out to about 85 per cent of the field of view. The easy to miss Ring Nebula, M57, was very simple to locate given the contrast of the view, though through this eyepiece it was very small indeed. Continuing our exploration we moved into Cygnus, where we examined the beautiful binary star Albireo and were impressed by the strong colours visible. We tested for colour aberrations
HOW SHIPS, CLOCKS AND STARS HELPED SOLVE THE LONGITUDE PROBLEM
300 years ago, in an attempt to solve one of the most pressing issues of the age, the British Government passed the 1714 Longitude Act, seeking a way to discover a ship’s position at sea. The official publication of the National Maritime Museum’s Ships, Clocks and Stars exhibition, Finding Longitude tells how this Act resulted in one of the most important collaborative efforts of all time.
Available to buy from all good booksellers and online. facebook.com/CollinsMaps
@CollinsMaps
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FIRST light AstroHutech Hinode SG See an interactive 360° model of this camera at www.skyatnightmagazine.com/huhinauto
solar autouider
A tenacious and effective accessory that you’ll wonder how you did without WORDS: PETE LAWRENCE
WWW.THESECRETSTUDIO.NET X 3, PETE LAWRENCE X 2
VITAL STATS • Price £545 • Power requirement USB 2.0 or 12V supply with a suitable adaptor • Extras Protective carry case • Size Detector (including finder dovetail) 120x63x 68mm; hand controller 117x32x71mm • Weight Detector (including finder dovetail) 291g; hand controller 110g • Supplier Ian King Imaging • www.iankingimaging. com • Tel 01580 212356
SKY SAYS… We even deliberately misaligned our mount, but the autoguider was not phased at all
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T
he AstroHutech Hinode SG solar autoguider has but one task in life, namely to keep a telescope pointing directly at the Sun. Autoguiding is most commonly used in long-exposure night-time imaging, when a dedicated guide camera feeds your computer with an image, which is monitored using software. If a designated star on the image drifts out of position, the program issues the necessary commands to the telescope mount to correct the situation. Of course, you don’t need to take long exposures of the Sun because it’s so bright. However, with daylight hiding every other star, it’s not possible to accurately polar align. For short solar imaging sessions a rough polar alignment is normally sufficient. For longer ones – public demonstrations or timelapse imaging, for example – the lack of alignment and having to constantly correct the telescope’s aim can be a real pain. This is where the Hinode solar autoguider comes to the rescue. The main part is a detector unit, which fits into a standard Vixen/Orion/ Sky-Watcher finder shoe and replaces the regular finderscope, which isn’t required for solar sessions. The detector connects to a hand controller, which can be hung on the mount by a small cord loop. Separate cables connect the detector unit to the hand controller and the mount autoguider port. Both ST-4 and Losmandy-type autoguiding mounts are supported.
Simple set up Power is supplied via a USB cable connected to either a computer’s USB 2.0 port or a 12V supply with a suitable adaptor – so it is not necessary to have a laptop present to operate the autoguider, although if you’re planning on photographing the Sun it’s certainly convenient to power it through one of the imaging computer’s USB ports. The device is easy to operate. A coarse solar finder is used to get you pointing in the right direction first. A simple LED display then shows where the autoguider is pointing and the device can emit audio tones to assist centring the Sun too. >
CLARITY OF PURPOSE The Hinode solar autoguider works superbly. Guiding is achieved by monitoring the Sun’s edge and so is not reliant on variable visibility features such as sunspots. The accuracy of the guiding can be adjusted by changing the ‘correction aggressiveness’ via the hand controller. In addition, a more accurate measurement of the Sun’s disc can be achieved by exposure averaging. This can be adjusted between one shot (no averaging), four shots or nine shots; the greater number of averaged shots, the greater the accuracy, although this will also slow the guider’s responsiveness slightly. Guide accuracy is stated to be typically 1.5 arcseconds or better, but this will depend on your setup and local seeing conditions. During our testing, the unit was certainly accurate enough to keep a highly magnified portion of the Sun’s disc aligned to our imaging camera frame for several hours at a time. The autoguider is tenacious. Forget to turn it off while moving to another part of the Sun’s disc and you’ll find the telescope obediently moving you back to where you had it pointing before.
Comparison of solar autoguided end frames in a 60-minute, 100-frame timelapse sequence
Comparison of solar autoguided end frames in a 30-minute, 37-frame, timelapse sequence
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COARSE FINDER The low-tech coarse finder is effective. When the detector is mounted into a telescope’s finder shoe, a raised, perforated plate on the front of the body creates a bright dot of sunlight. Everything is aligned to the Sun when the dot is made to sit on a target on a second raised plate at the rear of the detector.
GUIDER APERTURES Two apertures are visible at the front of the detector unit: these let the Sun’s image pass through to the electronics inside. They require no adjustment and simply need to be positioned so that they have an unobstructed view pointing directly towards the Sun.
USB 2.0 CONNECTION The detector unit gets its power from a USB connection. As only power is required, this doesn’t necessarily have to be plugged into a computer. However, if the cable is connected to a computer, additional software, available from the AstroHutech website (www.sciencecenter.net/ hutech/Hinode-sg/code/ index.htm), can be used to monitor the output of the guider on a PC.
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WWW.THESECRETSTUDIO.NET
> Once aligned, you need to calibrate the guider.
This is really simple, requiring nothing more than the press of a button. The hand controller’s LEDs flash away while calibration occurs, which can take a couple of minutes, but once done can be stored and recalled for future sessions without having to recalibrate again. As mount characteristics may change with the scope pointing either side of the meridian, a separate morning and afternoon calibration profile can be stored and recalled. We used the guider many times and it performed perfectly on most occasions. Capturing images for
HAND CONTROLLER The hand controller is operated through a set of buttons and also has LED indicators. The interface is simple but extremely effective. Two main modes of operation are provided: ‘Guide’ activates the autoguider, while ‘Finder’ turns it off so you can centre up another part of the Sun’s disc.
timelapse sequences was simple: a number of ours extended to several hours in length, but the autoguider did a great job of keeping the correct part of the Sun in view. This was especially impressive when we came to recording the movement and changes of prominences over several hours. Even at high magnification, the autoguider managed to keep the features of interest on the camera’s chip the majority of the time. We tested this using a softwaregenerated crosshair to mark a target feature. We even deliberately misaligned our equatorial mount far more than you would achieve by poor guessing. The autoguider didn’t seem phased by this at all and still managed to keep the scope pointing accurately. Amazingly, it dealt with clouds quite well too, only giving up the ghost when the Sun’s disc virtually disappeared from view. When this happens, a descending tone sounds to indicate guiding has been interrupted. If the clouds do clear again, the guider sounds an ascending tone and moves back to the original guide position. There’s no doubt that this is a niche piece of kit and it isn’t particularly cheap. However, for serious timelapse work, or for all-day solar monitoring with a non-permanent setup, the Hinode solar autoguider is invaluable. For public solar demonstrations and outreach work, you’ll wonder how you ever managed without it. S
VERDICT BUILD & DESIGN CONNECTIVITY EASE OF USE FEATURES TRACKING/GUIDING ACCURACY OVERALL
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SKY SAYS… Now add these:
1. Lunt LS60 Ha solar telescope 2. iOptron SkyGuider mount 3. Additional mounting bar
SPEAKER Audible tones are used to indicate that certain operations are ongoing or completed – they provide feedback when you’re trying to centre the Sun in the detector, for example. A descending tone sounds if autoguiding is interrupted by clouds, followed by an ascending tone if the clouds clear, allowing autoguiding to recommence.
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Books
RATINGS HHHHH Outstanding HHHHH Good HHHHH Average HHHHH Poor HHHHH Avoid
New astronomy and space titles reviewed
You can order these books from our shop by calling 01803 865913
The Cosmic Cocktail Three Parts Dark Matter
DAVID PARKER/SCIENCE PHOTO LIBRARY
Katherine Freese Princeton Press £19.95 z PB “Without having learned the language of mathematics, it can look like a string of to detect these ghostly particles which, as meaningless symbols and its beauty is their name suggests, interact too weakly hard to access.” to be seen directly. Here Katherine Freese, one of the The book explains what they are and why pioneers and key players in the field of they’re our best hope, before describing the dark matter and particle astrophysics, hits current and future experiments hunting on one of the main problems in popular for this missing piece of the cosmic puzzle. science writing – one that she quite Unfortunately, here the book deteriorates successfully overcomes in her new into a sea of acronyms, which is book, The Cosmic Cocktail. confusing and also quite Freese traverses the boring to read. astrophysics timeline, There are other things from the composition, that are off-putting history and geometry – for example, Freese of the Universe to dark weaves her own matter, antimatter, personal narrative neutrinos, quarks, into the physics the Higgs boson and story quite well, but the various candidates some sections are we have in the dark quite irrelevant and matter line up. disrupt the flow. However, Considering the this is minor as the personal complexity of the subject anecdotes become less frequent matter, Freese successfully WIMPs are the bestaccepted candidates and the complexity of the treads the line between for dark matter content rises. Despite these assuming too much of her weaknesses, the author gets an awful lot readers and missing out key aspects right – perhaps the most valuable aspect is of the story to simplify it. However, some of the particle physics chapters become too how Freese gives context and insight into a complicated, with excessive detail, equations complex and fast-moving field. and diagrams popping into the text. HHHH+ After explaining why dark matter must exist, Freese unpicks all the possible NICKY GUTTRIDGE is a science journalist candidates for this elusive stuff, settling on and Hubble public information officer the one astronomers think to be the most likely: weakly interacting massive particles Reader price £13.99, subscriber price £12.99 (WIMPs). Freese is involved in attempts P&P £1.99 Code: S0814/1 skyatnightmagazine.com 2014
TWO MINUTES WITH DAVID KATHERINE FREESE What inspired you to write the book? The dark matter problem is a great unsolved mystery and here we are on the verge of solving it. Twenty-five years ago I proposed ideas and made calculations that persuaded experimentalists to build detectors to hunt for dark matter particles, and now it seems that these global efforts are coming to fruition. It’s a great story and I thought people should know about it. Why is it so important to find dark matter? Because it’s there! If we are right, there are billions of dark matter particles going through us every second. They don’t harm us, but still we want to know what they are. How far are we from solving the mystery? We think we are on the verge of it. A multitude of experiments, both in underground labs and via satellites in space, have found unexplained signals that could have their origin in dark matter particles. Many believe that discovery is around the corner. How have technical advancements in observations helped the search? When I made my calculations of the interactions of dark matter particles in laboratory detectors, we found expected count rates of less than one per kilogram of detector per day. Experimentalists were willing to try to build the detectors. No one thought that the sensitivity would be a thousand times better than we originally calculated by now, and it is. These are tremendous achievements! KATHERINE FREESE is the George E. Uhlenbeck Professor of Physics at the University of Michigan
BOOKS AUGUST 103
Starlight Detectives:
BOOK OF
TH E MO N T H
How Astronomers, Inventors, and Eccentrics Discovered the Modern Universe Alan Hirshfeld Bellevue Literary Press £13.99 z PB The subtitle of this excellent book sums up its aims and achievements well. In its pages we discover that the advancement of our understanding of the Universe is measured, not only in scientific achievement, but also in the men and women who brought this about. The cast of players includes not only better-known individuals but a host of lesser-known characters, the achievements of each and every one being given the recognition they deserve. All are real people, each playing an important part in the development of our journey from the
The New Moon Arlin Crotts Cambridge £24.99 z HB In the early 1950s European astronauts set forth for the Moon – at least in Tintin comics. Inspiring many of today’s European researchers, the adventure was based on scrupulous research. But after the actual Moon missions cartoonist Hergé learnt he had made a slip up. Tintin and his dog Snowy get trapped inside a lunar cave filled with water-ice – but Apollo revealed Earth’s ‘eighth continent’ was dry as a bone. Or is it? It turns out Hergé was simply ahead of his time. Columbia University astronomer Arlin Crotts’ new book recounts how our understanding of the Moon has shifted massively in the generation since we briefly touched it. The reality of lunar water is now established – Apollo rock samples actually proved this all along, but any dampness was originally interpreted as
purely visual astronomy of the early Victorian era through to the scientific discipline that is observational astrophysics. A blend of history and science, Starlight Detectives outlines the work carried out by these people and sets it against the social and contemporary backdrop of their lives. The personalities of the characters involved shine through, as well as their tenacity in their individual quests for knowledge. There are three main areas covered, these being the advent and growth of photography and the role it played in astronomical research; the emergence of spectroscopy and the way it enabled astronomers to read the messages in starlight; and the transformations made to telescopes in order to satisfy the ever-present call of observational astronomers for ‘more light’. Informative and entertaining, this is a must read for anyone with an interest in the history of astronomy.
HHHHH BRIAN JONES has written 15 books on astronomy and space Reader price £13.99, subscriber price £13.99 P&P £1.99 Code: S0814/4
terrestrial contamination. Water renders the Moon much more liveable, of course, and the author ponders what life might actually be like there: moondust would pose a health hazard, low gravity would make surfaces six times more slippery, and lunar night would be blue-tinged by earthlight. Exploring the possibilities the Moon offers for our next half century, Crotts does a lot of analysis – arguably too much – on why we stopped going and whether we might return. Starting with the Moon’s still-enigmatic creation, all relevant facts are here, but also a lot of meandering discussion such as US President Barack Obama’s space policy, the value of ISS and even Apollo’s kick-starting of David Bowie’s career. Detailed geological discussions might not be beginnerfriendly, though any lunar enthusiast should enjoy this fascinating if occasionally frustrating work.
HHH++ SEAN BLAIR writes for the European Space Agency website
The Knowledge Lewis Dartnell Penguin Press £14.99 z HB A virulent strain of avian flu has killed 98 per cent of the world’s population, but you have survived to watch the modern world decay around you. What pieces of human knowledge will you and your fellow survivors need to rebuild civilization? This is the premise of Lewis Dartnell’s The Knowledge: How to Rebuild Our World from Scratch. Marketed as a postapocalyptic reboot manual, it is actually an engaging and wide-ranging discussion of the scientific discoveries and technological innovations that underpin our lives. Starting with a stark accounting of the surprisingly rapid ways our world would shut down, burn, crumble and rot in the wake of a mass depopulation event, the book goes on to suggest priorities for scavenging in the immediate aftermath. Most of the book, however, presents what Dartnell believes to be the fundamental knowledge that survivors and their offspring would need to recreate millennia of human progress as quickly as possible. The Knowledge tackles an ambitious range of topics – from cultivating food to generating power, developing medicine and rediscovering the scientific method. While it is more detailed in places than this pre-apocalyptic reader required, the text is littered with fascinating facts and an infectious enthusiasm for science and technology shines through in the accessible and lively writing. Dartnell is an astrobiologist who studies the potential for extraterrestrial life. His book is an absorbing thought experiment which celebrates the insight and ingenuity which has made this habitable planet into a civilized world.
+++++ OLIVIA JOHNSON is an astronomer specialising in science education Reader price £12.99, subscriber price £11.99 P&P £1.99 Code: S0814/3
Reader price £22.99, subscriber price £21.99 P&P £1.99 Code: S0814/2
skyatnightmagazine.com 2014
104 GEAR AUGUST
Gear
Elizabeth Pearson rounds up the latest astronomical accessories
1
4 1 Vimech EQ6 Wedge Price À325 • Supplier Robtics +31 70 369 7910 • www.robtics.nl Developed to overcome problems with the EQ6 mount’s polar axis adjustment, this wedge allows you to speedily set up your equipment and position it accurately.
2 Celestron FeatherTouch Micro Focuser Price £219 • Supplier Tring Astronomy Centre • 01442 822997 • www.tringastro.co.uk This accessory replaces the standard focuser on a Celestron C11 or C11 EdgeHD, giving you fine control as you adjust.
5
3 KiWAKA iOS App Price £1.99 • Supplier Landka www.landka.com
2
Take a journey through the stars with a colourful cast of characters in this educational app for kids. With images and information supplied by ESO, the app teaches about the stars and constellations in an entertaining way.
4 Hotech SCA Laser Collimator Price £97 • Supplier SCS Astro 0800 018 1544 • www.scsastro.co.uk This high precision laser collimator is self centring, promising precise and repeatable results. The collimator natively fits 1.25-inch focusers and is supplied with a 2-inch adaptor.
5 Astronomy Waistcoat Price £69.99 • Supplier Tom Sawyer Waistcoats 01803 868960 • www.tomsawyerwaistcoats.co.uk
3
A field of stars and planets printed on high quality cotton makes this waistcoat an eye-catching addition to any wardrobe.
6 Starwave 110mm Guidescope Rings Set with Dovetail Bar Price £69.99 • Supplier Altair Astro 01263 731505 • www.altairastro.com Reduce the movement in your guidescope and increase its accuracy by upgrading the holding rings. This set comes with a 200mm dovetail bar that allows you to position the rings to the best separation.
skyatnightmagazine.com 2014
6
NIPON SCOPE & OPTICS
A wide range of Nipon telescopes, spotting scopes, binoculars, monocular, microscopes, and optical accessories available from Nipon Scope & Optics online store and from our UK warehouse. Digital eyepiece/camera and various camera adaptors for telescopes are also among our featured products. We offer spectacular savings with probably the best UK prices and express courier delivery for almost all Nipon optical instruments and accessories.
www.nipon-scope.com Tel: 0844 318 7890 E-mail:
[email protected]
106 EXPERT INTERVIEW AUGUST
WHAT I REALLY WANT TO KNOW IS…
What can a ‘rainbow’ tell us about Venus? Wojciech Markiewicz is studying a rainbow-like phenomenon observed on Venus’s cloud tops to learn about its atmosphere INTERVIEWED BY PAUL SUTHERLAND
ESA/MPS/DLR/IDA
V
enus is our inner planetary neighbour, but still a mysterious world due to its heavy veil of cloud. As ESA’s Venus Express nears the end of its mission, scientists have sent the probe dipping into the outer layers of its poisonous atmosphere to get a taste of what it is like. The team I am part of has found some fresh clues to the answer by observing a peculiar rainbow-coloured phenomenon called a glory on the Venusian cloud tops. We turned the Venus Express spacecraft when it was in a particular orientation in a bid to observe the glory. With the Sun directly behind the probe and shining onto the clouds, this circular pattern came into view. It is a feature that will be familiar to many who have looked out of an airplane window – a circular pattern of colours on the clouds. We were not able to perform the experiment with Venus for a long time because it is thermally very demanding on the spacecraft, and risky in exposing certain parts of the spacecraft to the Sun. Finally we found a way to do it and to our delight we captured the glory using the probe’s Venus Monitoring Camera. There are various theories for what causes the glory. Not everyone agrees on why or how they occur, but two important things are required to produce them apart from the alignment of the Sun, the probe and Venus being just right. Firstly, the cloud particles on which the sunlight shines have to be spherical. They don’t need to be liquid, though in terrestrial situations the effect is indeed usually caused by droplets in the clouds. Secondly – and this is very important – they all have to be almost exactly the same size. If you have a lot of variation in size, that destroys the pattern and you don’t see it. We realised straight away that the sizes of the concentric circles in the glory could tell us the sizes of the particles. Previous observations of Venus, skyatnightmagazine.com 2014
have led to the belief that the planet’s cloudy atmosphere is composed of particles or crystals of sulphuric acid, and our results showed that these particles must all be about the same size. But one thing we could not immediately explain was the way the intensity of the light given off varied across the pattern of circles. The relative positions of the lowest intensity and highest intensity areas away from the centre of the glory in our images could not be reproduced with sulphuric acid droplets alone, so that puzzled us for a while. The only way we could make the glory fit the observed pattern was by changing the properties of the particles in the droplets. We couldn’t do it by changing their temperature because the change required would be too great. However, altering the composition of the atmosphere would give us the necessary change. Venus Express imaged this glory on the cloud tops in 2011; it spans 1,200km
ABOUT WOJCIECH MARKIEWICZ
Dr Wojciech Markiewicz of the Max Planck Institute for Solar System Research in Göttingen, Germany, is principal investigator for the Venus Monitoring Camera aboard Venus Express. He has a special interest in planetary atmospheres.
Secret ingredients? Our studies showed that this could be achieved either by coating the particle with elemental sulphur or by putting a sprinkle of iron chloride into the droplets. This latter substance could also solve another riddle if it is identified as the mysterious cause of ultraviolet light being absorbed by Venus’s atmosphere, a phenomenon first observed almost 90 years ago and causes beautiful patterns in the clouds when observed in near-ultraviolet wavelengths. The iron chloride could furthermore explain a haze that is observed above and within the clouds, made up of submicron-sized particles. To build on our studies, we would like to send a probe to enter Venus’ clouds. A Japanese probe, Akatsuki, will do this if it successfully goes into orbit on its second attempt in November 2015. Similar missions have been proposed to NASA and ESA but not yet selected. Other possibilities include sending balloons or inflatables into the atmosphere, but for the moment that remains science fiction. S
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ADVERTISEMENT FEATURE
UK
Retailer Guide Find the right one for you: buy your telescope from a specialist retailer
I
t is quite easy to become daunted by the vast array of equipment that is available to today’s amateur astronomers. Different makes, different models, different sizes and optical arrangements – if you’re new to the hobby, how do you make sense of all these details and find the telescope that will show you the Universe? The answer lies in buying from a specialist retailer – somewhere that really knows what they’re talking about. Like the retailers in this guide, they’ll have the practical knowledge that will guide you towards the scope that won’t end up gathering dust in a cupboard. Today there are over 1,000 models of telescope to choose from – refractors and reflectors, Dobsonians and Newtonians, Schmidt- and Maksutov-Cassegrains. And just as important as the telescope is the mount it sits on; but do you go for equatorial or altazimuth, manual or Go-To? And what about accessories like eyepieces and finderscopes? That’s certainly a lot to consider before making a decision, but a specialist retailer will help you make that decision, taking important considerations like portability, construction and price into account. So if you need friendly, face-to-face advice and excellent aftersales service, free from biased opinions, specialist telescope retailers are the place to go for a helping hand through the technical literature and tables of figures. They’ll help you find a scope that combines quality and convenience at a price that’s right.
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TELESCOPE HOUSE Founded in 1785, Telescope House has been responsible for supplying many well-known Astronomers with telescopes and equipment. The late Sir Patrick Moore bought the majority of his telescopes from the company, including his very first instrument. With a friendly showroom in Surrey, a number one ranked retail website and a service centre with fully qualified staff, the company offers equipment from manufacturers such as Meade, Revelation, Coronado, Bresser, Skywatcher, Orion USA, TeleVue, Vixen and Explore Scientific. Whether it’s advice on your first telescope, to setting up advanced Astrophotography systems, the staff at Telescope House have a wealth of experience and instant access to the right stock to back it up.
01342 837610 www.telescopehouse.com
[email protected]
SHERWOODS Established for over 60 years, we at Sherwoods are one of the Midlands leading suppliers of astronomical telescopes, binoculars and accessories. Through our website and showroom we are able to supply optics from some of the world’s leading optical manufacturers including Celestron, Skywatcher and Meade at some of the lowest prices in the UK. We offer a full mail-order service including next day delivery on many items held in stock.
TRING ASTRONOMY CENTRE At Tring Astronomy Centre we know that choosing the right equipment can be a minefield, but we strongly believe that seeing telescopes in the flesh and talking to an expert in a relaxed environment can really help. That’s why we have a coffee machine, a fully stocked bicuit barrel, and 45+ telescopes on display. As well as representing leading brands such as Celestron, Sky-Watcher, Baader Planetarium, Altair Astro, Vixen, Opticron, AstroTrac, iOptron, Lunt, Starlight Instruments, ZW Optical and many more we also offer a hire service so you can even try before you buy! So what are you waiting for? Visit or contact Tring Astronomy Centre and lets talk Astronomy!
01442 822997 www.tringastro.co.uk
[email protected]
THE WIDESCREEN CENTRE The Widescreen Centre is London’s Astronomy Showroom, located in Sherlock Holmes territory off Baker Street in the heart of Marylebone - a family owned and run business since starting out in1971. Our experienced and highly knowledgeable staff will offer you quality, choice, expertise and service - see Celestron, Sky-Watcher, Meade, Orion, Tele Vue, APM, Takahashi and much, much more besides says Simon Bennett, Widescreen’s MD and lifelong amateur astronomer, “If the correct equipment is purchased it will give a lifetime’s enjoyment. This is our mission. We will never sell you anything you don’t need” Watch out for Widescreen at Star Parties and exhibitions throughout the UK.
01527 857500 www.binocularhouse.com
[email protected]
02079 352580 www.widescreen-centre.co.uk
[email protected]
GREEN WITCH
ASTRONOMIA
Green Witch is one of the UK’s leading suppliers of telescopes, binoculars and accessories for astronomy. Founded by former members of the Royal Greenwich Observatory in 1998, Green Witch is dedicated to helping you choose and use the equipment that is right for you. We also carry an extensive range of telescopes and binoculars for nature and leisure, which you are welcome to try before you buy. Whether you visit our showrooms or buy online you can be sure of excellent service.
Atronomia is the award-winning home of the biggest range of telescopes and binoculars on display in the South of England. With over 50 telescopes and even more binoculars, Astronomia brings you the widest choice from respected brands such as Celestron, Sky-Watcher, Meade, Vixen and more. Visit our store in the High Street, Dorking or check out the website. Take advantage of our fullprice trade-ins on all telescopes – if you upgrade within 12 months, you don’t lose a penny!
01924 477719 - Birstall, West Yorks 01767 677025 - Gransden, Beds & Cambs www.green-witch.com
01306 640714 www.astronomia.co.uk
[email protected]
The Southern Hemisphere in August With Glenn Dawes
WHEN TO USE THIS CHART The chart accurately matches the sky on the dates and times shown. The sky is different at other times as stars crossing it set four minutes earlier each night. We’ve drawn the chart for latitude –35° south.
RT O N
AN he r
p
DA
The northern evening sky is home to four gentlemen: Boötes, Hercules, Ophiuchus and Aquarius. However, there was another, now lost in antiquity. Look for mag. +0.8 Altair, the alpha star in Aquila, the Eagle. The bird’s body and tail – encompassing Eta, Kappa, Lambda, Sigma, Theta, Iota, Nu and Delta Aquilae – used to represent the servant Antinous. He was immortalised in the heavens for sacrificing himself, hoping to extend the life of his master, the Roman emperor Hadrian.
_
STARS AND CONSTELLATIONS
A lunar occultation of Saturn can be seen from mainland Australia on the evening of the 4th. Use a high-power eyepiece to get as much of the first quarter Moon out of the field of view. Saturn disappears behind its dark edge from Sydney at 21:22 EST, Melbourne at 21:24 EST, Brisbane at 21:19 EST, Adelaide at 20:22 CST and Darwin at 20:07 CST. From Perth the event happens in twilight (18:15 WST); Tasmania sees a near miss. Five minutes beforehand Saturn’s brightest satellite Titan is occulted.
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AUGUST HIGHLIGHTS
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THE PLANETS _ `
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rises around 22:00 EST mid-month. After midnight there is a drought of bright planets until Venus emerges low in the northeast dawn sky. Jupiter rises out of the Sun’s glare and by month’s end can be glimpsed low in the east 30 minutes before sunrise.
EAST
The evening sky belongs to Mars and Saturn. The former is northwest as it gets dark, the latter due north. By late August, Mercury will have returned to the western evening twilight sky, and Neptune will be at opposition and visible all night. Uranus
_
DEEP-SKY OBJECTS Another of M20’s prominent features is the double star H40, which lies close to the point that the dark lanes come together. Its mag. +7.6 and mag. +8.7 components, only 11 arcseconds apart, are certainly pretty. However, there is more to see here – each is also a double with mag. +10.5 companions, separated by 6 arcseconds and 2.3 arcseconds respectively.
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One of the most spectacular sights in Sagittarius is the Trifid Nebula, M20, (RA 18h 02.6m, dec. –23° 02’; pictured). Located 7° north of the spout of the Teapot asterism, M20 can be seen in the same binocular field as the Lagoon Nebula, M8. The Trifid Nebula has prominent dark lanes dividing its main bright emission nebula into three sections, hence its name.
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skyatnightmagazine.com 2014
STAR BRIGHTNESS:
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skyatnightmagazine.com 2014
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Excellent quality traditional styled binoculars. Rubber armoured, water resistant and BAK 4 optics.
Very high quality optics at a great price. Traditional styled binoculars featuring BAK4 prisms, fully coated lenses, Long eye relief, rubber armour body.
Ostara Elinor 10x50 £179.99 BAK 4 prisms, Fully multi coated , waterproof ERHRMXVSKIR½PPIH
HD 8x42 ......£69.99 HD 8x56 ......£99.99 HD 7x50 ......£79.99 HD 10x50 ....£79.99 HD 12x60 ....£89.99 HD 15x70 ....£99.99 HD 20x80 .£149.99 HD 20x80T .£249.99
Ostara Prophecy 10x50 The ultimate in high quality viewing. £299.99 Highest quality, full multicoated optics,
Visionary HD 15x70 only £ 99.99
prism and phase coatings for superb brightness, clarity and contrast. Waterproof and nitrogen ½PPIH*YPP]GLIGOIHERHXIWXIHMRXLI9/
Eyepieces & Accessories EYEPIECES/ACCESSORIES Plossl 5mm (1.25”)................................................................. £14.99 Plossl 10mm (1.25”) .............................................................. £14.99 Plossl 15mm (1.25”) .............................................................. £14.99 Plossl 20mm (1.25”) .............................................................. £14.99 Plossl 25mm (1.25”) .............................................................. £17.99 Plossl 30mm (1.25”) .............................................................. £17.99 Plossl 40mm (1.25”) ............................................................. £19.99 Super Wide angle 10mm (1.25”) ....................................... £39.99 Super Wide angle 20mm (1.25”) ....................................... £44.99 FF 8mm (1.25”) ....................................................................... £49.99 FF 12mm (1.25”) .................................................................... £49.99 FF 19mm (1.25”) .................................................................... £49.99 FF 27mm (1.25”) .................................................................... £49.99 SWA 26mm (2”) ..................................................................... £79.99 SWA 32mm (2”) ..................................................................... £79.99 SWA 38mm (2”) ..................................................................... £79.99 SWA82 8.8mm (1.25”) ...................................................... £129.99 SWA82 14mm (1.25”) ....................................................... £149.99 SWA82 24mm (2”) ............................................................. £199.99
102 ED
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£799.00
HUGE RANGE
of eyepieces and accessories Clearview Binoculars: Four Square Chapel, Mapplewell. S75 6GG. Tel 01226 383736.
www.clearviewbinoculars.co.uk Callers very welcome, please check website for opening times. Binocular Outlet: 01162 430 967, Check our website and visit us on shows and events throughout the UK:
www.binocularoutlet.co.uk
SURPLUS STORE
The Army Surplus Store: 01297 23867, High Street, Totnes, Devon, TQ9 5NN
www.thearmysurplusstore.co.uk
The Far-Sighted binocular company is a group of independent specialist optical goods suppliers. For more information please visit www.far-sighted.co.uk. Offers are subject to availability and at participating outlets only. Prices DQGVSHFL¿FDWLRQVDUHVXEMHFWWR change without notice.
