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Astronomy Now - Fevereiro de 2016

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Astronomy Now - Fevereiro de 2016

  1. 1. FULL GUIDE TO EUROPEAN ASTROFEST 2016 POLESTARPUBLICATIONS £4.75 February 2016 AWESOME AURORAEexploreTHEGREATESTLIGHT SHOWSinthesolarsystem ASTRONOMYNOWFEBRUARY2016•AWESOMEAURORAE•CERES’SALTYSECRETS•THENAMEGAME•VOL30NO2 saltyceres surrenders its secrets howDOASTRO OBJECTS GET THEIR NAMES? beginners guide to MARS howdarkis your sky? 001_Cover_Feb16.indd 1 11/01/2016 16:50
  2. 2. Sadr image courtesy Geoffrey Lenox-Smith Star Adventurer Available Now! NEW Sky-Watcher ‘Star Adventurer’ Multi-purpose mount. Stunning value from £219.00 (Shown here with Equinox 80ED) Full ‘Astro Photo’ Package incl. Counterweight, Shaft & Wedge £299.00 £279.00 Call Widescreen on (020) 7935 2580 Daystar Quark & Quark Combo ‘H-Alpha Eyepieces’ Solar Astronomy at The Widescreen Centre Introducing the NEW 5-element William Optics Star 71 Imaging OTA STAR-71mm f/4.9 Imaging OTA with FPL 53 glass. 5 elements, 3 groups, 45mm imaging circle. 2.5” focuser - M48 thread & Canon EOS adapter. Includes mounting rings and Vixen style dovetail. Weighs 2.4 kg with tube rings & dovetail. Optional dedicated 1.25” dielectric diagonal. An optional soft carry case is available separately. See the Star-71 at Widescreen’s events including Astrofest 2015 (Feb 6-7) and the monthly BSIA meetings. William Optics Star-71 from £949.00 ‘The best scope we’ve ever made’ - William Widescreen Knows William Optics Available Now at Widescreen “The Best Astronomy Software” Enthusiast • Pro • Pro Plus £149 £249 Starry Night Enthusiast v7.0 Also available £89 V7.0 here now from Simulation Curriculum Arguably the world’s premier marque and most desirable telescope. The Questar has been in continuous production since 1950 and is now available from The Widescreen Centre. Standard model 3.5” starts from £3,999.00 in London ETX80 • 90 LX90 • 200 • 600 • 850 Great deals on all Meade scopes Call us on (020) 7935 2580 today The Widescreen Centre Your One-Stop London Shop for • Quality • Choice • Expertise • Service 47 Dorset Street • London • W1U 7ND • Baker Street Your one-stop London shop for • Quality • Choice • Expertise • Service 47 Dorset Street • London • W1U 7ND • Baker Street The Widescreen Centre 47 Dorset Street • London • W1U 7ND • Baker Street • 020 7935 2580 • Passport Ticket Sunglasses Camera Powertank Powertank? 17Ah 22Ah Vacations will never be the same again. With Widescreen’s new Tracer Lithium polymer power packs, you can easily travel with enough power to see you through cloudless nights. No more fumbling for spare AA batteries and travel adapters. Flight legal in certain sizes, you can now carry with you what you need - and recharge it on the go. The long-awaited breakthrough in power cell technology is here for your telescope - and there’s no reason to run out of camera or mobile power too. Tracer Lithium Polymer 8Ah - £119.99; 10Ah - £149.99; 14Ah - £179.99; 22Ah - £229.99. All in stock now at Widescreen. We Know William Optics The William Optics ZS71 Here at Widescreen we get to understand all of our products. We’re hands-on experienced amateur astronomers and are passionate about getting you the right product. When our suppliers update a product or bring out a new one - we make sure we understand why. That’s why we like William Optics. A constantly evolving product line means you know that they are monitoring cutomer feedback & always striving to supply a better product - just like us. The new ZS71 is a case in point. With a reliable, full-size 2” focuser and a dedicated flattener, it will go anywhere with you. Even on vacation this winter. And at way under £500, it’s exceptional value. We think through everthing we sell to our customers. Not just the class-leading scopes from William Optics. If you buy from us, it’s a safe purchase, backed up by our own experience. We live in a mobile Universe. Set your sights high. And see for yourself this winter. The Zenithstar 71 Special Offer on ZS71 + Flattener 6:- £439.00 22Ah 02_widescreenad_Aug13.indd 2 08/07/2013 18:37 47 Dorset Street • London • W1U 7ND • Baker Street • 020 7935 2580 • Come to the Widescreen booth at Astrofest and see these famous products in action - SkyFi USB, SkyWire, Starry Night, and the multi- award winning ‘SkySafari 5’ App & desktop software. 6” £1280 CALL 8” £1925 CALL 9.25” £2249 CALL Celestron@ The Widescreen Centre! Astrofest Booths 7-9 See you there! Astrofest Booths 1-6 Lunt LS50 is in stock! Your One-Stop London Shop for • Quality • Choice • Expertise • Service 002_widescreenad_feb16.indd 2 11/01/2016 15:12
  3. 3. h w! r r’ e g 0 h D) o’ l. t, e 0 . m The Widescreen Centre News and Events Hot New Products & great deals in store now! This August - join us on Saturday 10th for a great family day out - the SouthWest Astronomy Fair at the Norman Lockyer Observatory at Sidmouth in Devon - EX10 0NY. See for more details. We’ll have our usual array of new products, best sellers, bargains and interesting items.... Call us (020) 7935 2580 and ask if there’s something you’d like to see. 47 Dorset Street • London • W1U 7ND • Baker Street • 020 7935 2580 • Widescreen supports The Baker Street Irregular Astronomers. Chance to check out our products after dark. *See for more details Canon 60Da body £1174.99 Vixen Polarie £ 399.00 Terms & Conditions can be found on our website. Join The Widescreen Centre and the BSIA in Regent’s Park this summer. It’s fun, it’s free and it’s for everyone. Let us show you how to take your Astronomy with you Travel Light Live off the Sky Widescreen: Lunt Solar Systems in London Canon 60Da DSLR body £1174.99 Vixen Polarie £ 399.00 Polarscope £179.00 Mini ball head £29.00 Sky Atlas 2000 £79.00 Astronomik EOS Clip Filters from £ 72.00 Flip Mirror £129.00 - £189.00 Meade Rucksack £49.00 20mm WA reticle e/p £99.00 Stay cool in the heat. Every month we join London’s coolest Astronomi- cal Society - The BSIA - in Regent’s Park for a relaxed evening of astro chat, observing and socialising. It’s fun. It’s free. And it’s for everyone. Out under the stars, we can show you exactly what you need to know. in real time to explore the skies. And fast-track you to the Universe. Following the Sun... New Tele Vue 85 w/dual-speed focuser £2049 Lunt LS152THa - A 6” H-alpha telescope But much, much more.... • top notch review from Sky At Night’s Pete Lawrence LS35, LS60, LS80, LS100 and LS152 available Ask us about CaK and white-light options SkyFi USB Wireless Scope Controller £149.95 SkyWire Wired RS232 Controller £59.00 SkySafari App v3.7 Available in the App Store NEW XX16g Goto Dob Now £3299 StarBlast 4.5” & 6” Tabletop Dobsonians. Ready assembled. Maximum fun and performance in the minimum time. £179.00/ £299.00 Control your Goto Telescope with your iPad, new iPad Mini, iPhone or iPod Touch - Great telescopes and accessories at Widescreen. Veil courtesy Gordon Haynes The Complete Delos line-up is on promotion at £250.00 each* Choose from 3.5, 4.5, 6, 8, 10, 12, 14 and 17.3mm focal lengths Tele Vue in London Telescopes. Mounts. Eyepieces. Barlows & Powermates. Accessories & Imaging See the world’s best from London’s Tele Vue Demostrating Dealer. Tele Vue: It’s Even Better Than You Imagined.... August 10th September sees the arrival of the hotly-anticipated Sky-Watcher EQ8. We will have this mount in stock, on display and in action at the Equinox Star Party, Kelling Heath. More next month on the new Flagship EQ8 mount... See - later this year on the weekend of 4th - 6th October 2013. NR25 7HW Next meetings August 14th September 11th New EQ8 from £2500 Next meetings August 14th September 11th* *until August 26th or while stocks last 18:37 uk t 6 The Widescreen Centre. For all your Astronomy needs The Widescreen Centre News & Events ‘Widescreen Telescopes Centre’ App Download for FREE today... Visit us at Asrofest 2016! Astrofest returns to London! The Widescreen Centre will be there, along with all the usual suspects including Tele Vue, Baader & Celestron, Questar, Astronomik, Avalon, Southern Stars/Simulation Curriculum, our famous Solar corner and much, much more besides... Passionate about Product • Passionate about Service Join us in Regent’s Park for a FREE Astronomy evening with the UK’s coolest Astronomical Society - The Baker Street Irregular Astronomers! Join our Monday February 15th MoonDay event for a spectacular night out! See Eclipse photo: Orion StarBlast 62 Simon Bennett NEW Hotly Anticipated... Damian Peach DVD Pt.2 In Stock Now! Pt.I & Pt II - only at Widescreen Available Now £22.99 each Next on the calendar! It’s In London February 5-6th 2016 The Universe returns to London this month! Join us at Astrofest 2016 in Kensington on Friday 5th and Saturday 6th February. Tickets on the door or in advance from Please visit Widescreen’s website New design, easier to navigate, easy to search. Check our prices too - we wont be beaten. Dowload our App for extra special show deals, and follow us on Facebook & Twitter in 2016! Make the leap to Tele Vue in 2016. I frequently get asked “Which Tele Vue eyepice should I buy first?” My answer - it doesn’t matter! As soon as you’ve experienced one, you will inevitably be drawn back for more. See the universe as it’s meant to be seen today. Tele Vue Optics, from Chester, New York. Nothing else comes 47 Dorset Street • London • W1U 7ND • Baker Street • 020 7935 2580 • - at The Widescreen Centre New Tele Vue DeLite at Astrofest! Your one-stop London 47 D Th 47 Dorset St www.widescreen-centr 17Ah 22Ah Vacations will never be the same again. W new Tracer Lithium polymer power packs travel with enough power to see you throu No more fumbling for spare AA batteries a Flight legal in certain sizes, you can now what you need - and recharge it on the go The long-awaited breakthrough in power technology is here for your telescope - an reason to run out of camera or mobile po Tracer Lithium Polymer 8Ah - £119.99; 10 14Ah - £179.99; 22Ah - £229.99. All in stock now at Widescreen. We Know William Optics The William Optics ZS71 Here at Widescreen we get to understand all of our products. We’re hands-on experienced amateur astronomers and are passionate about getting you the right product. When our suppliers update a product or bring out a new one - we make sure we understand why. That’s why we like William Optics. A constantly evolving product line means you know that they are monitoring cutomer feedback & always striving to supply a better product - just like us. The new ZS71 is a case in point. With a reliable, full-size 2” focuser and a dedicated flattener, it will go anywhere with you. Even on vacation this winter. And at way under £500, it’s exceptional value. We think through everthing we sell to our custom scopes from William Optics. If you buy from us, by our own experience. We live in a mobile Univ And see for yourself this winter. The Zenithstar 71 02_widescreenad_Aug13.indd 2 It’s back! 5th & 6th February in London. Widescreen will be there, booths 1-6 + 7-9. Visit us at the show- or see Widescreen Centre Personalised Gift Vouchers for any occasion Valid 1 year, Any amount. 2016 Eclipse photo: Orion StarBlast 62 Simon BennettEclipse photo: Orion StarBlast 62 Simon BennettM45 image by Gordon Haynes with Tele Vue NP127FLI visit 002_widescreenad_feb16.indd 3 11/01/2016 15:12
  4. 4. 4 | Astronomy Now | February 2016 CONTENTS Managing Editor: Steven Young Editor: Ben Gilliland Contributing Editor: Keith Cooper EquipmentConsultant:SteveRingwood NightSkyEditor:MarkArmstrong Webeditor:AdeAshford ContributingConsultants: AllanChapman,IainNicolson TechnicalIllustrator:GregSmye-Rumsby Design & layout: Steve Kelly, Graham Carr Proofreaders:PeterGill,MandyBailey Publisher: Steven Young Deputy Publisher: Steve Kelly Office Manager: Laurie Young Assistant to the Publisher: Heather Young Subscriptions Manager: Lexi Hunt Founding Publisher: Angelo Zgorelec Editorial Address: Astronomy Now, PO Box 175, Tonbridge, Kent, TN10 4ZY Tel: 01732 446110 Fax: 01732 300148 e-mail: Business Advertising Tel: 01732 446112 Fax: 01732 300148 e-mail: Classified Advertising Tel: 01732 446111 Fax: 01732 300148 Printer: Wyndenham Group (Heron) Subscription Enquiries Astronomy Now Subscriptions, PO Box 175, Tonbridge, Kent, TN10 4ZY. Tel: 01732 446111 Fax: 01732 300148 (9.30am–4:00pm Mon–Fri) e-mail: Trade Distributor COMAG, Tavistock Road, West Drayton, Middlesex, UB7 7QE. Tel: 01895 433600 Fax: 01895 433602 ISSN: 0951-9726 © 2016 Pole Star Publications Ltd. Drawings,photographsandarticlespublishedinAstronomyNowarefullyprotectedbycopyrightandreproductioninwholeorinpartis forbidden. OpinionsexpressedbycontributorsarenotnecessarilythoseoftheeditorsorPublisher. Ben Gilliland Editor Digital versions The first astronomy magazine designed to fit in the palm of your hand. Download from the App and Play Stores Visit our website for the very latest astronomical news, observing tips and reviews. From astro-fast to AstroFest Ithasn’t been an ideal season for amateur astronomy.As the winter nights drew in, so it seems did the clouds, and those of us of a star- gazing bent have found ourselves enduring an enforced period of abstinence – a sort of astro-fast if you will. Well, it’s almost time to say goodbye to the astro-fast and say hello to AstroFest (see what I did there?). On the 5th and 6th of February the great and the good of the planet’s astronomical community will descend on London for the Solar System’s premiere star-gazing event: European AstroFest. And what a feast of astronomical treats it promises to be! Dr Brian May will sweep you into another dimension with a stereoscopic space adventure and Megan Argo will tell you what happens when galaxies collide.Two of the biggest space missions of the decade will be high on the menu – with one helping served up by Rosetta mission scientist Matt Taylor, and another by New Horizons co-investigator John Spencer. Between courses, Lewis Dartnell will tease your tastebuds with potentially habitable exoplanets,Andrew Pontzen will ponder the existence of dark matter, and Debbie Lewis will give you a potentially life-extinguishing asteroid impact to chew on.And that’s just a tiny sample of the goodies on offer (a tasting menu if you will) – you can view the full menu on page 47 of this issue. If you can’t wait until the AstroFest feast (AstroFeast?) to satiate your hunger, fear not, for we have lashings and lashings of astronomical goodness sandwiched between the covers of February’s Astronomy Now. As an appetiser, we serve up a delightfully illuminating romp around the Solar System’s auroral light shows. On Earth, these ethereal, shimmering curtains of light inspire wonder and awe in all those who witness them, but the aurora are not unique to our planet. From Venus to Neptune, via the moons of Jupiter, Isadora Fontaine takes us on a tour of the aurorae that illuminate alien skies. Speaking of alien worlds, have you ever wondered how astronomers decide on the names of newly discovered astronomical objects? Or why we even bother to bestow names, often steeped in the mythology of planet Earth, to worlds that mankind is never likely to set foot upon? Keith Cooper investigates the hows, whys and controversies and looks at the increasing level of input the public has in the naming process. We all know how important a dark sky is to astronomy, but do you really know how dark your skies are? Dark-sky meters are supposed to eliminate the vagaries and subjectiveness from measuring night sky darkness, but is it that simple? John Rowlands shows us how to do it right. On the subject of light, Jenny Winder continues our series of articles investigating the electromagnetic spectrum.This month she delves into the most energetic part of the spectrum – Gamma rays – and what they reveal about the mechanisms that drive some of the most violent events in the cosmos. On the off-chance you are still hungry for more, we have the usual smörgåsbord of regulars for you to snack on until the coffee arrives. Now that I’ve stretched the food-related metaphor to breaking point, it’s time to sign off until the March issue of Astronomy Now goes on sale on the 18th of February. See you at AstroFest! 004_editorialcontents_Feb16.indd 4 11/01/2016 16:52
  5. 5. • Control your telescope right from your device using SkyPortal Wi-Fi module and SkyPortal App. • Tap any celestial object you see in the sky to identify it immediately. • Slew your telescope to over astronomical 120,000 objects. • Works with Celestrons’ brand new planetarium App, SkyPortal. • SkyPortal App turns your smartphone or tablet into your own personal planetarium. • You can listen to hundreds of included audio descriptions and view hundreds of images through your device. • iOS and Android compatible. • Download the free SkyPortal App and start discovering today! Celestron®, SkyPortalTM and StarSenseTM is a registered trademark or trademark of Celestron Acquisition, LLC in the United States and in dozens of other countries around the world. All rights reserved. David Hinds Ltd is an authorised distributor and reseller of Celestron products. iPhone and App Store are registered trademarks of Apple Inc. Google Play is a registered trademark of Google Inc. A SOLID FOUNDATION DESIGNED FROM THE GROUND UP 12031 – Advanced VX 8 EdgeHD Camera not included Engineered from the ground up with astroimaging in mind, the new Advanced VX series from Celestron sets a superior standard in mid-level telescopes. Advanced VX provides you with many of the features found on Celestron’s most sophisticated German equatorial mounts, at an extremely affordable price. 12026 - Advanced VX 8 SCT 12031 - Advanced VX 8 EdgeHD 12046 - Advanced VX 9.25 SCT 12067 - Advanced VX 11 SCT 12079 - Advanced VX 6 SCT 22020 - Advanced VX 6 R 32054 - Advanced VX 6 N 32062 - Advanced VX 8 N 91519 - Advanced VX Mount Availablefromspecialistastronomyretailersandselectedotherdealersnationwide. CelestronisdistributedintheUK&IrelandbyDavidHindsLimited.Tradeenquirieswelcomed. TECHNOLOGICALLYSUPERIOR • Set your telescope outside, press ‘Align’ on the StarSense hand control, and sit back. No further user involvement needed! • StarSense uses an on-board digital camera to scan the sky. • In about 3 minutes StarSense will gather enough information to triangulate its position and align itself. • No need to identify or manually locate alignmentstarsinthesky,StarSensewill automatically align your telescope. • Sky Tour mode will slew to all the best stars, planets, galaxies and more based on your exact time and location. • Provides advanced mount modelling. Celestron WiFi Module Control your Celestron computerised telescope using your smart device* StarSense AutoAlign Accessory Upgrade your Celestron computerised telescope to a fully automatic computer set up* * See website for compatibility * See website for compatibility iPhones shown not included TM JN100715_CELESTRON_FULLPAGE-ANOW-AW.indd 1 23/7/15 10:21:43 132_OBCad_sep15.indd 132 07/08/2015 17:53
  6. 6. CONTENTS 6 Volume 30 • Number 2 • February 2016 • ISSN 0951-9726 • Printed in the UK Navigate to your favourite Astronomy Now articles in this issue. REGULARS60 THE NIGHT SKY 37 THE NAME GAME The naming of astronomical objects is no simple matter, on occasion leading to acrimony and controversy, but which now also has increasing input from the public, writes Keith Cooper. 9 News update 26 Key moments in astronomy 60 The night sky 88 The Universe for beginners 94 Imaging for beginners 99 Ask Alan 100 Astro-imaging masterclass 111 Book reviews 112 Astroloot 116 Grassroots astronomy 118 Astrolistings 120 Classifieds 123 Picture gallery 62 Top targets for beginners 66 Moonwatch 68 Sky scene 70 Southern sky 72 Object of the month 77 Planets at their best in 2016 78 Deep Sky challenge 80 Constellation of the Month 30 TRIPPING THE LIGHT FANTASTIC We are all held in awe by the beauty of the aurorae that dance in the skies of the Earth’s northern and southern hemispheres, but these etherial curtains of light aren’t unique to our planet. Isadora Fontaine takes a trip around the Solar System’s auroral displays. 14 Andromedae Veritate (from the Latin ‘veritas’, meaning truth) Spe (meaning ‘hope’ in Latin) HD 104985 Tonatiuh (Aztec god of the Sun) Meztli (Aztec goddess of the Moon) 51 Pegasi Helvetios (Latin phrase referring to a MedievalCeltic tribe that lived in Switzerland) Dimidium (Latin for ‘half’, because the planet is half the mass of Jupiter) 18 Delphini Musica (Latin for ‘music’) Arion (ancient Greek poet) HD 149026 Ogma (in Celtic myth Ogma is thegod of eloquence and writing) Smertrios (Gallic god of war) xi Aquilae Libertas (Latin for ‘liberty’) Fortitudo(Latin for ‘fortitude’) 42 Draconis Fafnir (a character from Norse mythology whoturned from a dwarf into a dragon) Orbitar (A play on the word ‘orbiter’)47 Ursae Majoris Chalawan (A mythological crocodilefrom a Thai folk tale) Taphaeo Thong Tapheo Kae (These are sistersassociated with the samefolk tale about Chalawan) Copernicus (named after Nicholas Copernicus) Harriot (named after Thomas Harriot, who may have been the first to use a telescope for astronomy) Galileo (named afterastronomer Galileo Galilei) Brahe (named afterastronomer Tycho Brahe) 55 Cancri Lippershey (named after Hans Lippershey, theoptician who invented the telescope) Janssen (named after Jacharias Janssen, who invented the microscope and may have had involvement in the telescope’s invention) Cervantes (the Spanish author of the Don Quixote stories) Quijote (lead character inthe Don Quixote stories) Dulcinea (Don Quixote’s love interest) mu Arae Rocinante (Don Quixote’s steed)Sancho (Don Quixote’s squire) Lich (a fictional undead creature that has magical powers to control other undead creatures) Draugr (undead creatures of Norse mythology) Poltergeist (A malevolent ghost or spirit) PSR 1257+12 (pulsar) Phobetor (the Greek god of nightmares) epsilon Tauri (Ain) Amateru(a Japanese appellation forshrines to the Shinto goddessof the Sun, Amaterasu) iota Draconis (Edasich) Hypatia(an ancient Greek scientistand philosopher) gamma Cephei (Errai) Tadmor (a Semitic name and modernArabic name for the city of Palmyra,which is a World Heritage Site) Geminorum (Pollux) Thestias (the patronym of Leda andAlthaea, daughters of Thestius and Leda mother of Pollux and his twin Castor) alpha Pisces Austrini (Fomalhaut) Dagon(a semitic deity represented ashalf-man, half-fish – theconstellation Pisces Austrinusis known as the Southern Fish) epsilon Eridani Ran (the Norse goddess of the sea) AEgir (Ran’s husband andgod of the ocean. The use ofthe capital E is to differentiateit from one of Saturn’s moons called Aegir) Titawin (a World Heritage Site in Morocco and a point Saffar (named after a scientist upsilon Andromedae of contact between Spanish and Arab civilisations, and between Europa andAfrica, after the 8th century) and mathematician in 11thcentury Andalusia) Samh (named after an astronomerMajriti (named after a mathematician and scientist who taught in 10th and 11th century Andalusia) and mathematician in 11th century Andalusia) HD 81688 Intercrus (means ‘between the legs’ in Latin, Arkas referring to the star’s position between the legs of the Great Bear, Ursa Major) (the son of Callisto, whowas also known as UrsaMajor, in Greek mythology) 004_editorialcontents_Feb16.indd 6 11/01/2016 16:52
  7. 7. February 2016 | Astronomy Now | 7 CONTENTS ON THE COVER: Thismonthwe takeatourofthe SolarSystem’s auroraldisplaysand discoverhownewly- discoveredobjects gettheirnames. 84 HOW DARK IS YOUR SKY? The introduction of dark-sky meters has made measuring night sky darkness easy. Or has it? John Rowlands takes a closer look at how to get it right. 105 BEYOND THE RAINBOW: GAMMA RAYS Last month, we introduced you to the Electromagnetic spectrum and its uses in modern astronomy. In this issue, Jenny WWinder begins our detailed journey through the spectrum. We start at the most energetic end of the spectrum: Gamma Rays, and we explore what they reveal about the workings of the Cosmos. s the ing) s undead creature that has magicalo control other undead creatures) Draugr (undead creatures of Norse mythology) Poltergeist (A malevolent ghost or spirit) Greek god of nightmares) Morocco and a point after a scientist en Spanish and Arabbetween Europa andter the 8th century) matician in 11th tury Andalusia) n astronomer nd scientist Andalusia) y Andalusia) 54 CERES’SALTY SOLUTION As Dawn spirals ever closer to enigmatic Ceres, scientists celebrate the solving of a major mystery on the dwarf planet. 004_editorialcontents_Feb16.indd 7 11/01/2016 16:52
  8. 8. The Infinity For stunning views in seconds. The Infinity breaks the barrier between visual observing and astrophotography. It combines the experience of observing at the eyepiece with a level of depth and detail that would traditionally be the result of several hours processing. This takes a camera that's sensitive enough to capture faint details on distant objects, and fast enough to do it in real time. It then takes our powerful, intuitive software to bring stunning views of the night sky to a screen in just seconds. This recreates the feel of observing in the field through a very large telescope, only using much more modest equipment. You stay connected to the night sky, watching satellites drift across your field of view, while viewing objects previously out of reach to all but the most powerful eyepieces and the largest apertures. See the faint connecting filaments in MSl while planning your next move in your star atlas. See bok globules in the Pelican Nebula as you dodge the clouds. Dive deep into the NGCs of Andromeda - and do it all in colour. Although our eyes aren't sensitive enough to see the universe in colour, the Infinity is. Faint grey fuzzies become detailed areas of colourful nebulosity, allowing you to go beyond the limits of our vision. But our own vision isn't our only limitation. Light pollution is a growing problem for all of us, with backyard observing becoming increasingly difficult in many places. The Infinity helps you cut through the pollution to bring observing back to our urban areas. It also helps you share the breath-taking things we see and discover as astronomers. By cutting the queue to the eyepiece, the Infinity allows everyone to explore the night sky not just together, but at the same time. You can discuss details and anomalies as you see them, and remove the need for special skills in averted vision. This makes it the perfect tool for public outreach, as well as observing with family and friends. But the Infinity doesn't just provide you with incredible live views. It also allows you to save single images and even whole sessions to share later. You can even broadcast your session live online to a global audience, right from inside our software. But surely something this advanced involves additional specialist equipment and complex software? That's the best bit. The Infinity is Atik Cameras are available from most major astronomy retailers. For a full list of stockists, visit us online. designed to work from a focal length of around 300mm right through to 1500mm. It works with alt/az fork-mounted telescopes as well as equatorial mounts. As long as you can track a star for a few seconds, it will work with an Infinity, without the need for complicated guiding systems. The camera itself uses the latest in CCD technology to provide incredible sensitivity at very low noise, and it's all controlled through our custom built software. You want to spend your time exploring the universe, not learning our program, so we've kept it as simple and intuitive as possible while still giving you the power and control you need to delve deep into the night sky. Want to know more? Find us at: :111ATIK•••• CAMERAS 008f) 008_atikad_jan16.indd 8 07/12/2015 12:47
  9. 9. For news updates, visit NEWS UPDATE T he mystery of the puzzling blue stragglers appears to have been solved, thanks to Hubble Space Telescope observations that indicate they are created when matter transfers from a red giant to a smaller companion star. The discovery, made by a team led by Robert Mathieu of the University of Wisconsin–Madison and including his former student Natalie Gosnell, who is now at the University of Texas, involved Hubble observations of the open star cluster NGC 188, which is 5,500 light years away in the constellation Cepheus. Blue stragglers are most obvious in star clusters, where all the stars are approximately the same age. Astronomers have noted that some stars in clusters appear too hot and blue for their age, as measured against the age of the cluster. Hence they ‘straggle’ behind the evolution of the other cluster stars. Is this strange state of affairs caused by the collision and merger of stars, or by binary star systems transferring matter from one star to the other? In the latter scenario, a red giant star would lose its diffuse outer atmosphere to a smaller, close-by star. The smaller star is rejuvenated by the extra material, while the red giant is whittled down to become a white dwarf. In 2011 Mathieu and Aaron Geller of Northwestern University in Illinois used the WIYN telescope on Kitt Peak in Hawaii to determine that over three-quarters of blue stragglers have companions, but what kind of companions are they? Analysing subsequent data from Hubble, Natalie Gosnell found that of 21 blue stragglers in NGC 188, seven had white dwarf companions. Another seven showed evidence of mass transfer. Taken together, the results indicate that at least two-thirds of the blue stragglers in NGC 188 are created through mass-transfer. This fraction could be even higher since Hubble is only able to detect white dwarfs no older than 300 million years. The observations, published in the 1 December 2015 issue of The Astrophysical Journal, are the first direct evidence that blue stragglers form by stealing mass from a neighbouring red giant. However, this does not completely rule out the possibility that some blue stragglers may form from collisions between stars. “It’s definitely possible that collisions dominate blue straggler formation in dense systems, like the cores of globular clusters”, Gosnell tells Astronomy Now. “And we think that several blue stragglers in NGC 188 are also formed through collisions, but not as many as those formed through mass transfer.” Vampiric blue stragglers feed off red giants NEWSupdate 9 An artist’s impression of the mass transfer process as a smaller companion steals gas from a neighbouring red giant to give itself new life as a blue straggler. Image: NASA/ESA/A Feild (STScI). 009_News_Feb16FIN.indd 9 11/01/2016 19:28
  10. 10. For news updates, visit 10 | Astronomy Now | February 2016 NEWS UPDATE What is a Damped Lyman- Alpha system? Lyman-alpha is the name given to a series of spectral lines emitted by neutral hydrogen gas in galaxies. In a 'Damped Lyman-Alpha' (DLA) system of the kind observed by Jeff Cooke and John O’Meara, intervening gas clouds with a high ‘column density’ (i.e. the density of material in an imaginary cylinder with a cross-sectional area of a square centimetre, driven through a given region of space between a light- emitting object and an observer) of at least 2 × 1020 atoms per cubic centimetre dampen the Lyman-alpha emission lines, broadening them. The DLAs are thought to be immense clouds of primordial gas that wander t h r o u g h i n t e r g a l a c t i c space, following the cosmic web of dark matter. In the early Universe many o f t h e m e x p e r i e n c e d gravitational collapse. As the clouds collapsed, they began to spin, while in their centres temperatures and pressures grew high enough to spark intense star-formation, building what we see as the central bulges of spiral galaxies today. The spiral discs came later as more gas fell onto the galaxies. This picture of galaxy formation is given only in broad brush strokes. With Cooke and O’Meara’s observations of the DLAs, coupled with the launch of the James Webb Space Telescope in 2018 and the construction of the next generation of extremely l a r g e g r o u n d - b a s e d telescopes, astronomers will finally be able to take greater steps towards rendering this picture in sharper focus. REPORTS FROM THE 227TH AMERICAN ASTRONOMICAL S Primordial gas clouds found silhouetted against distant galaxies T he true size of vast but dark clouds of gas that are large enough to create entire galaxies has been discovered silhouetted against the light of distant background objects. The first galaxies are understood to have formed from the collapse of giant clouds of hydrogen gas called ‘Damped Lyman-Alpha’ systems, or DLAs (see box). Most of this galaxy formation took place in the billion or so years after the Big Bang, but some of the DLAs remained. Previously those clouds that survived the initial round of galaxy formation were detected by the way they absorb the light of more distant quasars. However, the light- producing regions of quasars are the centres of active galaxies, which are relatively small. There was no way to determine the sizes of the DLAs by the amount of quasar light they obscured. Jeff Cooke of Swinburne University of Technology in Australia and John O’Meara of St Michael’s College in Vermont, USA, realised that if they could detect the clouds obscuring entire galaxies then it would provide a better estimate of their size. These background galaxies would, however, be very distant and very faint, so, to that end, the astronomers turned to some of the largest telescopes in the world – the Keck telescopes on Mauna Kea in Hawaii and the Very Large Telescope (VLT) at the European Southern Observatory in Chile. “Our new method first identifies galaxies that are more likely to have intervening DLAs and then searches for them using long, deep exposures on the powerful Keck Observatory ten-metre telescopes in Hawaii and deep data from the VLT eight-metre telescopes in Chile”, says Cooke, who presented the results at the 227th American Astronomical Society meeting. The degree by which the clouds block the light of a background galaxy gives an indication of their immense size. Now that some of these clouds have been identified, Cooke and O’Meara hope that further investigation will be able to help piece together how galaxies like the Milky Way are assembled from the raw materials in these clouds. “The technique is timely as the next generation of giant 30-metre telescopes will be online in several years and are ideal to exploit this method to routinely gather large numbers of clouds for study”, adds O’Meara. An artist’s impression that depicts how the light from a distant galaxy is partly absorbed by a foreground DLA cloud before reaching Earth. Image: Adrian Malec and Marie Martig. 009_News_Feb16FIN.indd 10 11/01/2016 19:29
  11. 11. For news updates, visit February 2016 | Astronomy Now | 11 NEWS UPDATE SOCIETY MEETING, FLORIDA, 4–8 JANUARY 2016 T wo massive blasts from the black hole at the centre of a nearby galaxy have given the clearest picture yet of how galaxies expel gas. Observations with NASA’s Chandra X-ray Observatory reveal two arcs of hot material near the centre of NGC 5194, which is the smaller partner in the Messier 51 system, more famously known as the Whirlpool. Eric Schlegel, who presented the findings at the 227th meeting of the American Astronomical Society, believes the two arcs to be relics of powerful shock waves from the black hole that erupted between three and six million years ago and that have ‘snow ploughed’ their way through the surrounding gas. “It’s the best example of snow- ploughed material I’ve ever seen”, says Schlegel. “It’s clearly a way of ejecting gas from a galaxy.” NGC 5194 and its larger spiral partner, NGC 5195, gravitationally interact with each other. These interactions have disturbed gas within NGC 5194, causing it to crash towards the massive black hole. This material was then either slingshot around the black hole, or fell directly onto it, resulting in a powerful burst of X-rays that rippled through the surrounding environment like a shockwave. Surrounding gas is heated to the point that it can no longer form stars and the shock wave blows the gas out of the galaxy. Astronomers call this process feedback and it is believed to be the major factor in stopping the growth of massive galaxies. “We would expect this process to happen much more in the early Universe, where galaxies were crammed in together and there were more collisions”, he says. “We need to study the process at other wavelengths – I’ll be spending the next few years looking at this.” Whirlpool’s partner has black hole burp TheWhirlpool Galaxy and its companion, NGC 5194. The inset image shows the black hole (centre) and two expanding arcs beneath it. Image: NASA/CXC/ STScI/University ofTexas/E Schlegel et al. 009_News_Feb16FIN.indd 11 11/01/2016 19:29
  12. 12. 12 | Astronomy Now | February 2016 NEWS UPDATE For news updates, visit Five more stars like the mighty eta Carinae, which lurks at the centre of this expanding nebula, have been found in nearby galaxies. Image: Jon Morse (University of Colorado)/NASA. REPORTS FROM THE 227TH AMERICAN ASTRONOMICAL SOCIETY MEETING, FLORIDA, 4–8 JANUARY 2016 Five twins of the Milky Way’s most mysterious star found in nearby galaxies A stronomers using the Hubble and Spitzer space telescopes have found a quintet of stars in other galaxies that are just like one of the most mysterious stars in our Galaxy: eta Carinae. Famous for its violent outburst in 1843 when it became the second brightest star in the sky and expelled huge amounts of material into space, eta Carinae is a stellar monster. It’s actually two stars, one 90 times more massive than the Sun, the other 30 solar masses, and combined they are five million times more luminous than the Sun. Eta Carinae is also an incredibly rare type of star, with no others quite like it known in our Galaxy, nor anywhere else in the Universe, until now. Rubab Khan, at NASA’s Goddard Space Flight Center, set out to find some more stars like eta Carinae. He developed a spectral fingerprint to search for them in mid-infrared and ultraviolet light. The dust expelled by these stars during outbursts blocks some of the optical and ultraviolet, and then re-radiates it in infrared light. So the fingerprint that Khan was searching for was an excess in infrared as seen by Spitzer, and a dip in optical and ultraviolet light as seen by Hubble. Lo and behold, Khan was able to identify five stars just like eta Carinae in nearby galaxies: NGC 6946, Messier 101, Messier 51 and two in Messier 83. It is perhaps no coincidence that these four galaxies are also the most prodigious producers of core-collapse supernovae within a 30 million light year radius, suggesting a connection. “These stars are very rare and now we can qualitatively say how rare they are”, says Khan, who presented his work at the American Astronomical Society Meeting. “We are finding one of these stars for every few hundred billion stars. Their discovery opens a new window into studying the evolution of high-mass stars, how they live, how they erupt and how they die.” The findings are published in the 20 December 2015 edition of Astrophysical Journal Letters. 009_News_Feb16FIN.indd 12 11/01/2016 19:29
  13. 13. 013_opticstarad_feb15.indd 13 11/01/2016 15:18
  14. 14. 14 | Astronomy Now | February 2016 For news updates, visit www.astronomynow.comNEWS UPDATE A giant, early galaxy cluster T he most massive galaxy cluster ever found in the early Universe has been identified by the cumulative efforts of the Hubble, Chandra and Keck telescopes. “Galaxy clusters are the most massive collapsed objects in the Universe and, as such, they are really at the crossroads of astrophysics and cosmology”, says Mark Brodwin of the University of Missouri in Kansas City, who announced the discovery at the 227th American Astronomical Society meeting in Florida. How big galaxy clusters can become depends on how fast they can grow before dark energy expands the Universe so much that the clusters become starved of new material falling onto them.As such, the masses of galaxy clusters in the early Universe are a means of measuring the expansion of the Universe during the first few billion years after the Big Bang.The light from this new king-sized galaxy cluster, designated IDCS J1426.5+3508 or known as IDCS 1426 for short, has been travelling for ten billion years, which puts it at less than four billion years after the Big Bang. Browdin and his colleagues used different technique’s to measure the cluster’s mass. Hubble and Keck were able to see the amount of gravitational lensing from the cluster and determine how much mass it needed.The Chandra X-ray observatory measured the amount of hot gas, while the Combined Array for Research in Millimetre Astronomy (CARMA) telescope – which ceased operations in 2015 – was able to measure the effect that the cluster’s gravity has on the cosmic microwave background radiation and determine the mass from that.All three methods came up with the same value: 400 trillion solar masses, or a thousand times the mass of the Milky Way. Chandra observed that its core of hot gas was not as hot as might be expected from a newly formed cluster. Instead the gas had cooled somewhat as the cluster dynamically ‘relaxed’ – a feature usually seen in more evolved galaxy clusters.This core of gas is offset from the centre of the cluster by about 100,000 light years.This is evidence for a collision about 500 million years earlier with another large cluster.The resulting merger may have sped up its evolution. “When it is hit by another cluster, the cool core can slosh around like wine in the bottom of a wine glass”, says Brodwin.“Eventually it will settle towards the centre, but it hasn’t settled yet, and that’s how we know it was a recent merger.” IDCS 1426 will not have stopped evolving ten billion years ago.Today it likely resembles one of the largest galaxy clusters in the Universe, like a super-cluster of galaxies such as the Coma Cluster. The findings will be published in a future issue of The Astrophysical Journal. AAS meeting round-up Distancemattersinbinarybirths It may be possible to tell how different binary star systems form by looking at the separation of their stars, according to astronomers probing star-forming regions with the Very Large Array radio telescope in New Mexico, USA. The study, led by John Tobin of Leiden Observatory, found that over half of newborn stars are in systems of two or more and that they could be split into two broad categories: one where the separation between the stars is around 75 astronomical units (AU), and the other where the distance is around 3,000 AU. Stars with large separations, say the astronomers, formed through the turbulent fragmentation of the proto-stellar cloud of gas, whereas closer partners form in the disc of material that surrounds the original proto-star. The black hole missing its stars A galaxy a billion light years away and thought to have been involved in a merger with another galaxy has been found sporting two large black holes, but strangelyoneofthemismissingitsretinueofstars. The two black holes are thought to have originated in the centres of two galaxies that merged to form the galaxy that we see today, called SDSS J1126+2944. Supermassive black holes usually come with a swarm of stars around them, yet one of the black holes in SDSS J1126+2944 has 500 times less stars than the other. According to Julie Comerford of the University of Colorado, Boulder, the black hole may have lost its stars to gravitational tides during the merger. An alternative explanation is that the black hole with no stars is of intermediate mass (around 100,000 solar masses), which would mean that one of the galaxies that mergedwasadwarfgalaxy. “There are very few intermediate mass black holes known“, says Comerford, who presented the results at the AAS meeting. “They are hard to find, but they are an important evolutionary step towardsbuildingasupermassiveblackhole.” The quasar that turned itself off A quasar that was active just twelve years ago has been seen to suddenly shut down, suggesting that the black hole at its heart has consumed all the gas within its vicinity. The Sloan Digital Sky Survey (SDSS) measured the spectra of the quasar in 2003, in particular noting the strength of hydrogen- alpha emission from gas falling towards the black hole. However, when the SDSS looked again in 2015, the strong hydrogen-alpha emission had dropped by a factor of 50 and the quasar looked like a normal galaxy. “This is the first time we’ve seen a quasar shut off this dramatically, this quickly“, says Jessie Runnoe of Penn State University, who led the study and presented the results at the AAS meeting. A composite image of IDCS 1426, incorporating visible light observations from Hubble, the presence of hot gas (blue) seen by Chandra, and infrared light (red) seen by the Spitzer Space Telescope. Image: NASA/ESA/M Brodwin (University of Missouri). REPORTS FROM THE 227TH AMERICAN ASTRONOMICAL SOCIETY MEETING, FLORIDA, 4–8 JANUARY 2016 009_News_Feb16FIN.indd 14 11/01/2016 19:29
  15. 15. 39_Starlightxpressad_Apr13.indd 39 11/03/2013 19:55
  16. 16. For news updates, visit 16 | Astronomy Now | February 2016 NEWS UPDATE Dry planets are wet beneath the clouds T he closest known potentially habitable planet beyond our Solar System has turned up orbiting a red dwarf star just 13.8 light years away. Astronomers from the University of New South Wales in Australia used the HARPS (High Accuracy Radial velocity Planet Searcher) on the 3.6-metre telescope at the European Southern Observatory’s facility in La Silla, Chile, to discover three Nearest potentially habitable planet found H ot jupiters that had appeared dry as a bone are hiding water vapour under thick clouds, according to a new study courtesy of the powerful optics of the Hubble and Spitzer space telescopes. In 2014 Hubble observations indicated that three hot jupiters, which are giant planets extremely close to their stars, seemed devoid of water vapour in their atmospheres (see News update, AN, September 2014). Hubble had observed the planets by comparing the light of each individual planet and its star combined, and the light of just the star when the planet was behind it. The difference between the two is the light of the planet, and spectroscopic analysis of that light can indicate which molecules in each planet’s atmosphere are absorbing light. There didn’t seem to be much water. Now we know why. An international team, including astronomers at the University of Exeter, surveyed ten hot jupiters – including the dry trio observed in 2014 – in both optical light and infrared light, courtesy of Spitzer. Sometimes the planets appear larger, depending on the wavelength of light they are observed in: infrared light can penetrate deeper into the atmosphere and hence a planet can seem smaller compared to when it is viewed in optical light, which can be reflected by high-altitude clouds. The difference between optical and infrared wavelengths gives some indication as to whether a planet has a cloudy or relatively clear atmosphere. “Our results suggest it’s simply clouds hiding the water from prying eyes”, says Jonathan Fortney from the University of Calfornia, Santa Cruz, who is a team member and co-author on a paper describing the results in the 14 December 2015 issue of the journal Nature. “We can therefore rule out hot, dry, jupiters.” This will come as a relief to scientists, who had feared that the lack of water vapour in these planets’ atmospheres meant that something was amiss in our understanding of how exoplanets form. An artist’s impression of three worlds orbiting a red dwarf. Image: NASA/JPL–Caltech. An artist’s impression of HD 189733b, a blue gas giant among those thought to have had a shortage of water. Image: NASA/ ESA/M Kornmesser. worlds orbiting the star, named Wolf 1061 (see this month’s Picture gallery for an image of this star). All three planets have a low enough mass (1.4, 4.3 and 5.2 times the mass of Earth respectively) to probably be rocky and one of the planets, 1061c, is tucked snugly within the star’s habitable zone, where temperatures may be ideal for liquid water to exist on the planet’s surface.The other two worlds orbit their star just inside and outside of the habitable zone, and the outermost planet, d, could also potentially be habitable if it has a thick enough atmosphere and a strong axial tilt. The HARPS instrument had been used to search for planets around Wolf 1061 previously with only hints of their existence, but improved data processing techniques allowed the Australian team to tease out the subtle Doppler shift measurements required to detect the planets. In all, the team studied more than ten years’ worth of observations of Wolf 1061, which is in the constellation Ophiuchus, close to the globular cluster M107. Recent observations of powerful flares on red dwarfs (see News update, AN, January 2016) suggest they can be deadly to life on planets orbiting them. Nevertheless, activity on red dwarfs can vary. Astronomers are seeking to discover whether these planets also transit their star, which would make them prime candidates for future study by upcoming missions such as the European Space Agency’s PLATO spacecraft. “It is fascinating to look at the vastness of space and think a star so very close to us – a near neighbour – could host a habitable planet“, says Duncan Wright of the University of New South Wales and lead author of a paper describing the discovery in a forthcoming issue of Astrophysical Journal Letters. 009_News_Feb16FIN.indd 16 11/01/2016 19:29
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  18. 18. For news updates, visit 18 | Astronomy Now | February 2016 NEWS UPDATE B lack holes can grow no larger than 50 billion times the mass of the Sun through the process of swallowing gas, according to Professor Andrew King of the University of Leicester. The supermassive black hole at the centre of a galaxy grows most rapidly when it is consuming vast amounts of gas from a doughnut-shaped disc, or torus, around it. The more massive the disc, the hotter it becomes and we see these discs as quasars. When the inner regions of the disc lose energy through friction and gravitational tides, the gas can spiral into the black hole. However, these discs of gas are inherently unstable and they often collapse to form stars. King found that a black hole could grow to 50 billion solar masses through the process of accretion before its gravitational tides were sufficient to destroy the disc. Without a disc, the black hole cannot grow any further from accretion, only through merging with stars or another black hole, neither of which requires a disc. “The significance of this discovery is that astronomers have found black holes of almost the maximum mass, by observing the huge amount of radiation given off by the gas disc as it falls in”, says King, whose work is to be published in a forthcoming issue of Monthly Notices of the Royal Astronomical Society. “The mass limit means that this procedure should not turn up any masses much bigger than those we know, because there would not be a luminous disc.” Meanwhile, NASA’s NuSTAR X-ray telescope has peered into the gas torus around a black hole for Gravitational lens makes supernova reappear Black holes reach their mass limit Thanks to the lensing power of a massive galaxy cluster, astronomers have for the first time been able to predict the appearance of a supernova. In November 2004, the Hubble Space Telescope spotted multiple lensed images of the same supernova, produced by dense concentrations of foreground matter warping space and bending the light of the supernova along different paths. The galaxy cluster doing the lensing – MACS J1149.5+2223 – is located five billion light years away, whereas photons from the supernova have been travelling for ten billion years. The different paths taken by the light of the supernova each incur a different time delay. By modelling the distribution of mass in the cluster, astronomers led by Tommaso Treu of the University of California, Los Angeles, predicted that another image would appear by the end of last year. Sure enough, the supernova reappeared on 11 December 2015. Alas, says Treu, the resolution of the Hubble image is not sufficient to reveal the progenitor star, so we cannot determine the behaviour of the star in the run-up to its destruction. The discovery, however, might have greater cosmological importance. In 1964 Norwegian astronomer Sjur Refsdal predicted that time-delayed images of supernovae could be seen through gravitational lenses, and hence this exploding star has been nicknamed the Refsdal supernova. Refsdal suggested that by accurately calculating the time delay between images, it might be possible to measure the expansion of the Universe. “We can in principle use the supernova to measure the expansion rate of the Universe, once we have measured the time delay“, Treu tells Astronomy Now. “We’ll have to monitor for several months – possibly a whole year – before we can determine the the first time and found it to be clumpy. Along with the European Space Agency’s XMM-Newton space telescope, NuSTAR observed the disc around the black hole at the centre of the galaxy NGC 1068. The findings, to be published in the 11 February 2016 issue of Monthly Notices of the Royal Astronomical Society, might explain why some black holes are obscured by their disc, while others are not. The aim is now to figure out what is causing the gas to form clumps: is it turbulence in the disc, or does material rain onto the disc in clumps from outside? Black holes can grow to 50 billion solar masses before their surrounding disc of clumpy gas is destroyed. Image: ESA/V Beckmann (NASA GSFC). time delay precisely. However, whether the measurement of the expansion rate of the Universe will be sufficiently precise to be interesting will depend on how accurately we can measure the time delay and how accurate we can make the lens models.” The multiple paths of the supernova’s light as it passes through the galaxy cluster on its way towards Earth. Image: NASA/ESA. 009_News_Feb16FIN.indd 18 11/01/2016 19:29
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  20. 20. For news updates, visit 20 | Astronomy Now | February 2016 B asaltic rocks investigated by China’s Chang’e-3 mission to the Moon have been found to sport a slightly different mineralogical composition compared to the Moon rocks brought back to Earth by the Apollo astronauts. The findings indicate that the interior of the Moon may not be as uniform as previously thought. Chang’e-3 landed in the northern part of Mare Imbrium in 2013. Imbrium is one of the younger lunar floodplains, at around three billion years old. Its surface is smooth, with a thinner layer of crumbly regolith (dirt and dust) on top of the bedrock, which has proved crucial. Normally regolith is so thick and filled with debris that it hides the bedrock and makes it difficult to discern from orbit. Chang’e-3 and its little rover, Yutu, were able to sample the bedrock directly. “We now have ‘ground truth’ for our remote sensing, a well- characterised sample in a key location”, says Bradley Jolliff of Washington University, who participated in a collaboration between Chinese and American scientists to publish the findings in the 22 December 2015 issue of the journal Nature Communications. “We see the same signal from orbit in other places, so we now know that those other places probably have similar basalts.” The difference between the Imbrium basalts and basaltic rocks from other regions on the Moon is the concentration of titanium. The Apollo and Soviet Luna missions returned rocks to Earth from older lava plains on the Moon that had either very high or very low amounts of titanium, whereas the rocks that Chang’e-3 inspected have medium concentrations and were also richer in iron. The relative titanium abundances highlight differences in the mantle where the lava originated from. “The diversity tells us that the Moon’s upper mantle is much less uniform in composition than the Earth’s”, says Jolliff. “We’re still trying to figure out exactly how this happened. Possibly there were big impacts during the magma ocean stage that disrupted the mantle’s formation.” NASA’s Curiosity rover has detected surprisingly high concentrations of silica in rocks embedded within geological layers up the flanks of the five-kilometre tall Mount Sharp. Silica is a chemical compound of oxidised silicon and the levels of silica discovered by Curiosity are much higher than has been seen anywhere else on Mars so far. In some cases, Curiosity discovered rocks that were nine- tenths pure silica. “You can boost the concentration of silica either by leaching away other ingredients while leaving silica behind, or by bringing in silica from somewhere else“, says Albert Yen, who is a Curiosity science team member at NASA’s Jet Propulsion Laboratory (JPL). “Either of these processes involves water.” Acidic water could have carried other materials away, leaving behind the silica. Alternatively, alkaline or neutral pH water could have deposited dissolved silica when the water evaporated. Discovering which was the case will tell us more about the history and nature of water on ancient Mars. Intriguingly, one of the silica-rich rocks investigated by Curiosity was found to contain its silica in a mineral called tridymite. This mineral is rare on Earth, forming in high temperature volcanic or metamorphic rocks (which are ordinary rocks that change their chemical or physical properties when exposed to high temperatures), but tridymite has never been found on Mars until now. Volcanic rock can evolve to become rich in silica, but the silica-rich rocks that Curiosity has found are thought to have been laid down on a lake bed billions of years ago. It suggests that volcanism may have been the root cause behind the silica, but that subsequent water action resulted in the concentrations of silica that we see today. Silicon Mars: was its water acidic or alkaline? A view of geological layers on the flank of Mount Sharp. Image: NASA/JPL–Caltech/MSSS. Volcanic rocks reveal the Moon’s uneven interior A artist’s impression of Chang’e-3’s rover,Yutu, on the ground at Mare Imbrium. Image: CNSA. 009_News_Feb16FIN.indd 20 11/01/2016 19:29
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  23. 23. For news updates, visit February 2016 | Astronomy Now | 23 NEWS UPDATE R aging storms are known to be common in the atmospheres of gas giant planets and nearly-stars called brown dwarfs, but a joint effort by NASA’s Kepler and Spitzer space telescopes has spotted a storm on a star. Admittedly, the star in question is a timid one. Called W1906+40, it belongs to a class of stars known as L-dwarfs. Although some L-dwarfs are brown dwarfs, others like W1906+40 are thought to be proper stars that Below: a trio of bow shocks imaged by WISE and the Spitzer SpaceTelescope. The infrared images are presented in false colour. Images: NASA/JPL–Caltech/ University of Wyoming. Spitzer sees stormy star fuse hydrogen in their cores, judging by their age and temperature. Still, W1906+40 is fairly cool for a star, with a temperature on its photosphere (the star’s visible ‘surface’) of just 2,038 degrees Celsius. For comparison, the Sun’s photosphere is about 5,500 degrees Celsius. “The star is the size of Jupiter and its storm is the size of Jupiter’s Great Red Spot”, says John Gizis of the University of Delaware, USA, who is lead author of a study describing the enormous storm in the 10 November issue of the The Astrophysical Journal. The star itself was discovered by NASA’s Wide-field Infrared Survey Explorer (WISE) in 2011, lying around 53 light years away. It was not until later that Gizis and his team realised that W1906+40 was actually in the field of view of the Kepler Space Telescope, which originally stared at a patch of sky in the constellations of Cygnus and Lyra. The storm is so large that when it rotates into view every nine hours it causes the star’s light to dip. Kepler detected this dip, but originally scientists interpreted it as starspot. It was only when the Spitzer Space Telescope followed up that it was revealed to be a cloudy storm laden with mineral grains that has persisted for at least two years now. If you could travel to W1906+40 in person, you would see the storm as a dark spot close to the star’s polar regions. It is the best evidence yet that cool stars can have storms and dark spots like giant planets and brown dwarfs, further blurring the lines between these low mass objects. An artist’s impression of the star with the dark, churning storm. Image: NASA/JPL– Caltech. Speeding stars caught ramming through space Like cosmic speed cameras, NASA’s infrared Spitzer and WISE telescopes have caught hundreds of stars racing breakneck through the Galaxy, piling up gas in front of them in what are called‘bow shocks’. Some stars lead frenetic lives, reaching velocities of around 86,400 kilometres per hour. They arrive at these tremendous speeds following events in their past that propel them on their way. “Some stars get the boot when their companion star explodes in a supernova, and others can get kicked out of crowded star clusters“, says William Chick of the University of Wyoming, who led the research. As they move through the Galaxy they are shielded by a magnetic buffer blown by their stellar winds, much like our Sun’s solar wind creates the magnetic heliosphere surrounding the Solar System. The hotter and more massive a star, the stronger its stellar winds and the larger its magnetic bubble. Coupled with how fast a star is moving, the magnetic bubble can plough through gas in the interstellar medium that lies in the star’s path, creating a bow shock of compressed gas ahead of it, like how a boat pushing through water creates a wave in front of it. These bow shocks are warm, so they glow brightly in infrared light. Chick and his colleagues scoured archival data from the Spitzer Space Telescope and the Wide-field Infrared Survey Explorer (WISE) to search for the best bow shock candidates. They found 200 and, when they followed up on 80 of the most promising, they discovered fast-moving massive stars inside most of them. The size of the bow shocks can provide information on things as diverse as the density of the interstellar medium and the magnetic field strength of the star. Meanwhile, a group of Argentinian astronomers is tackling the problem from the opposite direction. Led by Cintia Peri of the Argentine Institute of Radio Astronomy, they are first finding the speedy stars and then trying to detect a bow shock. “WISE and Spitzer have given us the best images of bow shocks so far“, says Peri. “In many cases, bow shocks that looked very diffuse before, can now be resolved, and, moreover, we can see some new details of the structures.” 009_News_Feb16FIN.indd 23 11/01/2016 19:30
  24. 24. 024_bresserad_feb16.indd 24 11/01/2016 15:30
  25. 25. For news updates, visit February 2016 | Astronomy Now | 25 NEWS UPDATE by Alan LongstaffTALKINGpoint Speculation or science? S tring theory and the multiverse dominate modern cosmology, but are they science or just speculative hypotheses that have come to be exempted from experimental verification? This was the subject of a workshop held at the Ludwig Maximilian University in Munich, Germany, in December 2015. It is a debate that has been a long time coming. For over a decade there has been increasing unease amongst some scientists about the speculative character of some ideas in physics. These concerns came to a head in the 18 December 2014 issue of the prestigious journal Nature when two internationally renowned scientists – cosmologist George Ellis of the University of Cape Town and astronomer Joseph Silk of Johns Hopkins University, Baltimore – issued a clarion call to ‘defend the integrity of physics’. They were responding to the view of some researchers that if a theory is sufficiently elegant and explanatory it need not be tested experimentally. This breaks with the generally accepted view of philosopher Karl Popper that for a theory to be scientific it has to be falsifiable; there has to be some experiment or observation that can show it is wrong. The workshop came about as a result of their Nature article. What are the issues? For Ellis and Silk, both string theory and the multiverse are ideas that cannot be refuted, i.e. they fail Popper’s test. They distinguish these from theories ‘that relate directly to the real world and are testable through observations’, such as dark matter and dark energy. String theory is seductive because it seems to offer a way to unify gravity with quantum theory and the mathematics is beautiful. However, conclusions arising from mathematics need not mirror what happens in reality, as we know from Steady State Theory. Their point is that the ‘strings’ of string theory are far too small to be detected currently and the theory relies on dimensions we can never observe. Refuting the multiverse? The multiverse idea comes in a couple of flavours; the kaleidoscope version requires an unfathomable number (10500 ) of other universes to exist simply to explain why our Universe has values for physical constants that allow us to exist. The ‘many worlds’ version branches into parallel universes every time an observation forces a quantum system to make a choice (think Schrödinger; dead cat/live cat) and is but one of several interpretations of the enigmatic machinations of quantum mechanics. However, no one can dream up a way to refute the existence of these other universes, even in principle. A counterargument that might work for string theory is that just because a theory cannot be falsified today does not mean that it can never be. After all, science lived happily with atoms and electrons long before they could be seen directly. Some have attempted to redefine what is meant by a scientific theory. Cosmologist Sean Carroll regards falsifiability as a ‘blunt instrument’, arguing that a theory is scientific if it says something unambiguous about how reality works and explains the data. The difficulty here is that often there are several equally good ways to account for the data, so how do we choose between them? A more worrying trend is that some string theorists cite internal consistency as a way of validating a theory, or even the lack of credible alternatives, i.e. if it’s the only game in town, it’s probably right. Now before you spill your coffee, it’s worth looking at the history of black holes. These objects are theoretical. No one has ever seen a black hole directly, i.e. the ‘shadow’ of the hole on the accretion disc as depicted in the film Interstellar. Yet black holes are pretty much accepted by the astronomical community to account for phenomena – e.g. gravitational effects, quasars – that we cannot explain in any other way. Unsurprisingly the ‘only game in town’ argument about string theory doesn’t cut ice with researchers such as Lee Smolin of the Perimeter Institute for Theoretical Physics in Canada and Carlo Rovelli, Aix-Marseille University, France, who are exploring another idea, loop quantum gravity, which they argue makes testable predictions. If theoretical physics loses its empirical moorings, this will provide greater purchase for pseudoscientists to peddle their nonsense. Now is not a good time to damage public confidence in science, when climate change and the theory of evolution are being denied by some politicians and religious fundamentalists, argue Ellis and Silk. The workshop probably didn’t change opinions, but at least it has kick-started a discussion on what is meant by the scientific method. Dr Alan Longstaff is a regular contributor to Astronomy Now. An artist’s take on the multiverse – are theories of parallel universes scientific? AN graphic by Ben Gilliland. 009_News_Feb16FIN.indd 25 11/01/2016 19:30
  26. 26. For news updates, visit 26 | Astronomy Now | February 2016 NEWS UPDATE SpaceX made big strides in the company’s quest to drastically cut the cost of spaceflight in December with the successful landing of a 15-story Falcon 9 rocket booster at Cape Canaveral on 21 December. The California-based launch provider delivered 11 commercial data relay satellites into low Earth orbit for Orbcomm, a US communications company, as the Falcon 9’s first stage manoeuvred back towards its Cape Canaveral launch site a few minutes after lift-off. The booster reignited one of its rocket engines to slow down and descend vertically to a landing zone about 10 kilometres south of the Falcon 9 launch pad. The recovery of the booster is a key step towarda making the Falcon 9 partially reusable, an objective long desired by SpaceX’s billionaire founder Elon Musk, who says the cost of space transportation must be reduced to achieve his vision of colonising Mars. The Falcon 9 landing came weeks after Blue Origin, a rival space company founded by Amazon’s Jeff Bezos, landed a suborbital rocket in November, but that feat was on a smaller scale than SpaceX’s rocket recovery experiment. SpaceX plans to test the used Falcon 9 booster to see how much refurbishment is required to fly the rocket again. Musk hopes to reuse a future Falcon 9 first stage this year. NASA announced in December that the InSight lander designed to detect seismic activity on Mars will not be ready for launch in March. The delay means the probe will not launch before May 2018, the next time Mars and Earth are in the right positions in the Solar System to make the interplanetary trip possible. Managers blamed leaks in a vacuum enclosure holding InSight’s French-made seismometers. The International Space Station completed a crew rotation in December, with three crewmen returning to Earth and another trio of residents blasting off to start a half- year in orbit. R u s s i a n c o s m o n a u t O l e g Kononenko, NASA astronaut Kjell Lindgren and Japanese flight engineer Kimiya Yui landed in Kazakhstan on 11 December to wrap up more than 141 days in space. Four days later, British astronaut Tim Peake, commander Yuri Malenchenko and NASA flight engineer SPACEFLIGHT NOWStephen Clark reports on the latest spaceflight news from Cape Canaveral. To find out more visit Key moments in astronomy A ndrew Claude de la Cherois Crommelin was – as his name does not immediately suggest – an Ulsterman. Born on 6 February 1865 at Cushendun, County Antrim, he was a descendent of Louis Crommelin. This seventeenth century entrepreneur revitalised the Irish linen industry. Andrew was to do much the same for cometary studies. Educated at Marlborough and Trinity College, Cambridge, even as a boy Crommelin was an enthusiastic astronomer. There was never much doubt as to his chosen career: he joined the Royal Observatory (RGO) in 1891, appointed as a ‘Second Class Assistant’. Humble though the position sounds, it was recognised as an entry point for young but exceptionally talented astronomers. Such prestige perhaps compensated for the wretched pay – a very mediocre £200 per year. Initially, Crommelin’s work involved lunar and cometary observations using the Greenwich Transit Circle,Airy’s Alt-azimuth and the Sheepshanks Equatorial telescope.All were – at a kindly assessment – approaching the end of their useful life. Yet they introduced Andrew to the field he made his own.As a writer in The Observatory in 1940 remarked,“to think of Crommelin was to be reminded of comets and minor planets".The path to his greatest achievement began in December 1906, when he read a paper to the Royal Astronomical Society, pointing out that the best predictions for the return of Halley’s comet varied by many years.Alongside his colleague, Philip Cowell, he intensively researched previous appearances, making extensive use of the latest observations of asteroids and gravitational effects. Crommelin and Cowell’s work, originally published in a series of papers between in 1907 and 1908, predicted perihelion to within three days of the event. Such accuracy was unprecedented, but their methods were so exact that they rightly believed the error reflected the influence of unknown, non-gravitational forces. These have since been identified as gaseous emissions from the nucleus of the comet, subtly diverting its course. Both authors were awarded the Lindemann Prize of the Astronomische Gesellschaft and doctoral degrees from Oxford University in recognition of their work. Crommelin was director of the British Astronomical Association’s comet section for many years and President of the Royal Astronomical Society from 1929 to 1931. He was also an avid observer of eclipses and was particularly pleased to have served on the 1919 expedition to Brazil, which played a major part in confirming Einstein’s General Theory of Relativity. A still more unusual honour came years after his death. In 1929 he identified four earlier comet discoveries as referring to a single entity. This became knows as Comet Pons–Coggia–Winnecke– Forbes. The name was so inconvenient that in 1948 it was officially renamed Comet Crommelin. In private life the astronomer was known as enormously well-read and deeply religious: He originally intended to take Anglican orders, but underwent a spiritual crisis in the year in which he joined the RGO, becoming a member of the Roman Catholic Church. Crommelin’s wife, Letitia, whom he married in 1897, died in 1921, whilst his eldest son Claude and youngest daughter Philomena were killed in a mountaineering accident in 1933. The astronomer died in an equally unexpected way, struck by a motor cycle during the blackout on 20 September 1939. Ian Seymour Gravity and gas Tim Kopra soared into space on a Soyuz rocket, reaching the space station about six hours later. Two more satellites joined Europe’s Galileo navigation system with a launch from the European spaceport in French Guiana on 17 December. The two new spacecraft are the eleventh and twelfth satellites for the Galileo network, a civilian-run analogue to the US military’s Global Positioning System, which is to be fully operational by 2020. Other launches in December included an Indian mission on 16 December with six satellites for Singapore, the launch of a Russian–European communications satellite on 24 December aboard a Proton rocket, and the 28 December lift-off of a Chinese observatory fitted with a telescope to peer down at Earth from geostationary orbit, a capability Chinese media says will help track US aircraft carriers in the Asia–Pacific. The first stage of a SpaceX Falcon 9 rocket descends to a landing pad at Cape Canaveral minutes after launching with 11 commercial communications satellites.Image: SpaceX. 009_News_Feb16FIN.indd 26 11/01/2016 19:30
  27. 27. Study from home with some of the world’s leading experts As one of the world’s leading providers of distance learning courses in astronomy, UCLan offers a variety of opportunities to study. Our University Certificates are designed for people with little or no prior subject knowledge. University Certificates: • ASTRONOMY • ASTROBIOLOGY • SUN, EARTH AND CLIMATE • COSMOLOGY Following completion of these courses, students can go on to further study leading to more advanced awards: • BSC (HONS) ASTRONOMY • CERTIFICATE OF HIGHER EDUCATION IN ASTRONOMY • DIPLOMA OF HIGHER EDUCATION IN ASTRONOMY Our website: All courses endorsed by the Royal Astronomical Society. BSc recognised by the Institute of Physics. Visit us at ASTROFEST UCL1187 Astronomy Advert_Layout 1 17/12/2014 16:59 Page 1 027_UCLANad_feb16.indd 27 11/01/2016 15:31
  28. 28. NUMBER 1 HOW TO ARTICLESIMPROVE YOUR OBSERVING FORIN-DEPTH TELESCOPE REVIEWS Subscribe today and save up to £19 off the price in the shops! • Never miss an issue of the UK’s biggest and best monthly astronomy magazine • Delivered to your door every month at no additional cost • Subscribers get massive saving off the price in the shops • Packed with more features than any other astronomy magazine * Offer available to new subscribers for UK delivery when you pay by direct debit.  Call: 01732 446111 Subscribe to the UK’s Subscriber delivery address: Name Address Postcode Country E-mail Telephone 3 EASY WAYS TO SUBSCRIBE 1. DIRECT DEBIT BESTVALUE! Pay £38 annually and recieve your FREE gift. You'll save up to £19 off the price in the shops. Available to new subscribers with a UK bank account and a UK delivery address. Instruction to your bank or building society to pay by Direct Debit: Service User Number 4 4 1 4 7 0 To: The Manager (Bank/Building Society) Address Postcode Name of Account holder(s) Bank/Building Society account number Branch Sort Code Instruction to your bank or building society Please pay PSL re Astronomy Now Direct Debits from the account detailed in this Instruction subject to the safeguards assured by the Direct Debit Guarantee. I understand that this Instruction may remain with PSL re Astronomy Now and, if so, details will be passed electronically to my bank/building society. Signature Date Banks and building societies may not accept Direct Debit Instructions for some types of account. 3. CHEQUE £42 (UK) £52 (Europe ) £58 (Rest of the world) Note: Payment by cheque must be in Pounds Sterling drawn on a UK bank or by Mastercard, Visa or American Express.Your email address and contact information will not be shared with third parties. SEND TO: AN SUBSCRIPTIONS, PO BOX 175, TONBRIDGE, KENT TN10 4ZY, UK Please send me the next 12 issues. I enclose a cheque made payable to Astronomy Now for: Card Number Expires Issue No. (if applicable) 2. CREDIT CARD £42 (UK) £52 (Europe ) £58 (Rest of the world) Please send me the next 12 issues Please debit my credit/debit card: Offer ends 29 February 2016 Select your FREE GIFT (Offer available to UK subscribers only) Hubble Special 2016 Yearbook & Calendar 028_subsad_feb16.indd 28 11/01/2016 17:07
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  30. 30. 30 | Astronomy Now | February 2016 TRIPPING THE LIGHT FANTASTIC T he aurora is one of nature’s most beautiful sights. Shimmering curtains of light in the sky, dancing around the Earth’s north and south magnetic poles, inspire wonder and amazement in those who have witnessed them. However, this phenomenon isn’t exclusive to Earth. Aurorae also occur elsewhere in the Solar System where there are magnetic fields and atmospheric gases to produce these marvellous lights. Jupiter If you thought the aurora on Earth was a sight to behold, wait till you see what it looks like on the gas giants! Jupiter’s magnetic field is ten times stronger than the Earth’s, so it’s not surprising that this planet also has aurorae, and they are huge – Jupiter’s aurorae could engulf the Earth many times over. Unlike the Earth’s ephemeral and intermittent polar lights, these thelight fantastic We are all held in awe by the beauty of the aurorae that dance in the skies of the Earth’s northern and southern hemispheres, but these ethereal curtains of light aren’t unique to our planet. Isadora Fontaine takes a trip around the Solar System’s auroral displays. The Aurora Australis observed from the International Space Station. Image credit: William L. Stefanov, NASA-JSC. 030_Aurora_Feb16FIN.indd 30 11/01/2016 11:47
  31. 31. February 2016 | Astronomy Now | 31 TRIPPING THE LIGHT FANTASTIC Solar wind Plasma Aurora Magneticfie ld Electron Electron Proton Alpha particle (helium nucleus) Oxygen molecule • Aurorae are caused by the interaction between charged particles from space, a magnetic field and atmospheric gases. • They are known as the Aurora Borealis, or Northern Lights, when they occur above the Earth’s north magnetic pole, and the Aurora Australis (Southern Lights) when they occur above the south magnetic pole. • As the solar wind buffets the Earth’s magnetic field, charged particles from the Sun and plasma from our planet’s magnetosphere are flung into the upper atmosphere, following magnetic field lines towards the magnetic poles. These energetic particles collide with molecules of atmospheric gas, causing them to emit photons and thus giving rise to the dazzling light show. Oxygen produces green and red aurorae, while nitrogen produces purple and blue light. • The aurorae on Earth are most often seen in the two ‘auroral ovals’ that encircle the north and south magnetic poles, at high latitudes. • Occasionally, during periods of high solar activity, the aurora intensifies, producing more vivid displays of light, and sometimes the auroral ovals migrate temporarily to lower latitudes. Whatisanaurora? Graphic: Ben Gilliland 030_Aurora_Feb16FIN.indd 31 11/01/2016 11:47
  32. 32. 32 | Astronomy Now | February 2016 TRIPPING THE LIGHT FANTASTIC the rotation of Jupiter’, states astronomer John Clarke from Boston University. ‘Other moons can contribute, but Io’s plasma dominates.’ As volcanoes on Io erupt, they release charged particles into Jupiter’s magnetic field. These particles then form a ring, or torus, of plasma stretching almost as far as Saturn’s orbit. The volcanically active moon also causes flares in the aurora, seen as bright spots that correspond with Io’s orbit. These arise when streams of erupted particles from Io interact directly with Jupiter’s atmosphere, rather than just contributing to the plasma torus. The other Galilean moons, icy Europa, Ganymede and Callisto, might also deliver charged particles to Jupiter’s plasma ring and cause flare-ups in its aurorae, but their effect is less well understood. Mars It may come as a surprise for a planet without magnetic poles, but Mars has its own aurorae. ESA’s Mars Express and NASA’s MAVEN spacecraft have been observing aurorae while in orbit around the red planet. These are transient and rare events, but are boosted during solar storms, which produce particularly energetic electrons to trigger aurorae deep in Mars’ thin atmosphere. ‘In the case of Mars, there is no global magnetic field and the aurora is observed in the southern hemisphere, where high-elevation terrains have kept part of the ancient magnetic field, before the dynamo effect (a magnetic field generated by a liquid metallic core, like that of the Earth), which sustained the global field, vanished a long time ago’, states Jean-Claude Gerard from the University of Liège, Belgium. A particularly intense aurora was spotted by aurorae are a permanent feature surrounding the Jovian poles, glowing an eerie shade of red, owing to emissions from Jupiter’s hydrogen-dominated atmosphere. They are also caused not by the Sun, as on Earth, but by Jupiter’s Galilean moons. (The solar wind plays a smaller part in causing Jovian aurorae.) ‘The ultimate plasma source for most of Jupiter’s aurora is the Io plasma torus, and the ultimate energy source is Jupiter’s aurora, showing the influences of the Galilean moons. Image credit: John T. Clarke (University of Michigan), ESA, NASA. X-ray aurorae as observed by NASA’s Chandra X-ray Observatory overlaid on a simultaneous optical image from the Hubble Space Telescope. Image credit: X-ray: NASA/ CXC/SwRI/R. Gladstone et al.; Optical: NASA/ESA/Hubble Heritage (AURA/STScI). IO SPOT POLAR OVALS TRANSPOLAR EMISSIONS EUROPA SPOTGANYMEDE SPOT DAYSIDE AURORA MAIN OVAL 030_Aurora_Feb16FIN.indd 32 11/01/2016 11:47
  33. 33. TRIPPING THE LIGHT FANTASTIC MAVEN’s ultraviolet spectrograph in 2014, nicknamed ‘the Christmas Lights’ because they were spotted in late December. This was a different, more diffuse type of Martian aurora to the ones previously seen by Mars Express. ‘This type of aurora is caused by energetic solar wind electrons that are accelerated on their way to Mars. When they arrive close to Mars, they follow open magnetic field lines to precipitate and excite the atmosphere’, states Arnaud Stiepen, also from the University of Liège. This causes carbon dioxide molecules in the atmosphere to emit photons, giving rise to blue aurorae. Gerard and Stiepen have tips for any future astronauts wishing to observe the Martian aurora. ‘You would not need to move to high latitude regions as on Earth, but you should be located in the southern hemisphere, in a specific longitude, to have a chance of seeing it. The aurora would probably be seen as a blue luminous arc extending east–west’, suggests Gerard. However, if a solar flare triggers an auroral display such as the ‘Christmas Lights’ of 2014, Stiepen says ‘astronauts anywhere on the planet would see the whole night sky painted in blueish colours!’ Saturn Not only does Saturn possess beautiful rings, it also has spectacular aurorae. The phenomenon has been photographed in detail by Hubble and Cassini in visible, ultraviolet and infrared wavelengths. Saturn’s aurorae are thought to be caused mainly by the action of the solar wind on the planet’s magnetic field. ‘I would say that Saturn is intermediate between the Earth’s and Jupiter’s auroral processes.  In all our data thus far, Saturn’s aurorae have responded every time there has been a large change in the solar wind’, states Clarke. This drives a current of about 1 million amps through its ionosphere that accelerates electrons at immense energies, causing the atmosphere to glow. However, Sarah Badman from Lancaster University suggests that at least one of Saturn’s moons also has an influence on the aurora. ‘Enceladus, which has water-ice plumes coming from its southern pole, sometimes produces an auroral spot in Saturn’s atmosphere.’ ‘Saturn’s aurorae are red, changing to pink and purple instead of the most common green colour of Earth’s aurora’, Badman states. As with Jupiter, excited hydrogen molecules in Saturn’s atmosphere produce the red colour. Images of Saturn’s aurorae show them to be blue or white, because they are taken at ultraviolet wavelengths. Like Earth, Saturn’s aurorae are sensitive to fluctuations as the stream of particles from the Sun strengthens and weakens, and they generally form in ovals around the magnetic poles. However, as Badman states, ‘unlike on Earth, the aurora can also elongate into a spiral shape because of Saturn’s rotation.’ While on Earth they tend to last minutes or hours, aurorae on Saturn last for days, and are at their brightest at dawn. As with Jupiter, Saturn’s polar lights are of an impressive size. ‘You could fit more than four Earths inside one of Saturn’s auroral ovals’, Badman adds. Streams of charged particles blasted from the Sun collide with Saturn’s magnetic field, creating an aurora on the planet’s south pole. Unlike Earth’s relatively short-lived auroras, Saturn’s can last for days. In this Hubble image the aurora appears blue, but a Saturn-based observer would see red flashes. Image credit: NASA, ESA, J. Clarke (Boston University), and Z. Levay (STScI). 33 030_Aurora_Feb16FIN.indd 33 11/01/2016 11:47
  34. 34. 34 | Astronomy Now | February 2016 TRIPPING THE LIGHT FANTASTIC An artist’s impression of MAVEN observing the Martian aurora. Image: University of Colorado. Composite images of Uranus, combining Hubble observations from 2011 of the aurorae in visible and ultraviolet light, Voyager 2 images from 1986 in visible light, and Gemini Observatory infrared observations from 2011 of Uranus’ faint rings. Image: NASA, ESA, and L. Lamy (Observatory of Paris, CNRS, CNES). Uranusand Neptune Images taken by the Hubble Space Telescope in 2011 show bright spots in the atmosphere of Uranus, which turned out to be aurorae. These images were taken during a period of heightened solar activity, showing solar particles to be the cause of these aurorae. The bright spots on the planet were located far from its poles, since the magnetic field of Uranus is tilted at 59 degrees from its spin axis. Aurorae on Neptune were first detected by the Voyager 2 probe as it passed by the planet in 1989. Little is known about Neptunian aurorae. They occur over wide areas of the planet rather than just at the poles, owing to the planet’s complex magnetic field, and they are also 200 times weaker than aurorae on Earth. 030_Aurora_Feb16FIN.indd 34 11/01/2016 11:47
  35. 35. TRIPPING THE LIGHT FANTASTIC 35 stream of plasma from Jupiter and you have the perfect recipe for northern and southern Lights. One of the most interesting outcomes of observing the aurora on Ganymede is that it suggests the existence of a large, deep ocean of liquid water under its thick ice crust. Observations made with the Hubble Space Telescope in 2015 showed that the deflections caused by Jupiter on the moon’s magnetic field were a lot smaller than expected, meaning that something else is generating a secondary magnetic field on Ganymede, the most likely culprit being an electrically conductive ocean of saltwater up to 330km deep, able to produce a magnetic field of its own. The presence of an ocean brings up the inevitable question on whether this moon might have life forms swimming in its subsurface waters. This has made Ganymede a target for the future ESA space mission Juice, due to launch in 2022, which will analyse Jupiter’s large icy moons and will be sent into orbit around Ganymede. Venus Like Mars, Venus does not have a global magnetic field, but there is evidence that it too has aurorae. As the solar wind interacts with Venus’ ionosphere, it produces a magnetised ‘tail’ of charged particles streaming away from the Sun, similar to a comet’s tail. ‘On Earth, aurorae only occur around the magnetic poles, but on Venus they are observed across the night side of the planet. The exact mechanism for solar wind particles in Venus’ tail to penetrate the night side of Venus is as yet unknown, however aurorae are only observed after solar storms, particularly coronal mass ejections’, states astronomer Candace Grey of New Mexico State University in Las Cruces. One theory is that heightened solar activity causes magnetic reconnection, a process that sparks aurorae on other planets, including the Earth, to take place within Venus’ magnetised tail. The magnetic field lines ‘snap’, propelling high-energy particles into Venus’ atmosphere, thereby producing green sky glows. ‘The bright green emissions observed on Venus are due to excited oxygen atoms’, Grey continues. Ganymede Aurorae outside the Earth are not limited just to planets. Ganymede, the largest moon in the Solar System, is also the only moon with a magnetosphere generated by a metallic core in a manner similar to that of the Earth’s magnetic field. In addition to this, the moon also has a thin atmosphere of oxygen. Add in a Auroraebeyond thesolarsystem In July 2015, the first ‘exo-aurorae’ were discovered, on a brown dwarf called LSR J1835+3259. They were discovered using radio observations by the Very Large Array in New Mexico. They are 10,000 times more powerful than any of the aurorae in our solar system, but their cause is a mystery. They could indicate the presence of planets orbiting LSR J1835+3259 producing plasma that interacts with the brown dwarf’s magnetic field (in a similar manner to the way plasma from Io sparks off aurorae on Jupiter), or they might be produced by the rapid rotation of the brown dwarf. Aurorae have not yet been detected on exoplanets, but there is no doubt that they exist and may be detected with more advanced telescopes in the future. The solar wind strikes Venus in this illustration, perhaps hard enough to spark aurorae. Image: C. Carreau/ ESA. An artist’s concept of aurorae on Jupiter’s moon, Ganymede based on observations by NASA’s Hubble Space Telescope Image credit: ESA and G. Bacon (STScI). Isadora Fontaine is a freelance science writer. 030_Aurora_Feb16FIN.indd 35 11/01/2016 11:47
  36. 36. Moravian Instruments CCD Cameras Behind the Best Astrophotographs Image on the background: Part of the Cygnus mosaic by Jean Claude Canonne Philippe Bernhard Didier Chaplain Laurent Bourgon Image stitched from 4 frames taken with G4-16000 cameras 365Astronomy (distributor UK & ROI) web: mail: tel: +44 2033 845187 Ktec Telescopes Ltd (dealer ROI) web: mail: tel: +353 85 2288 692 Telescope House Ltd (dealer UK) web: tel: +44 1342 837098 mail: Astrograph Ltd (dealer UK) web: mail: tel: +44 8433 304988 Tring Astronomy Centre (dealer UK) web: mail: tel: +44 1422 822997 The Widescreen Centre (dealer UK) web: mail: tel: +44 2079 352580 036_365ad_feb16.indd 36 11/01/2016 15:33
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