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Waves Gravitational Telescopes for KIDS p. 60 OCEAN WORLDS of the solar system p. 24 NOVEMBER 2017 The world’s best-selling astronomy magazine NEW RESEARCH Gravitational waves From novelty to science p. 18 Discover autumn’s A pair of black holes spiral together, unleashing a brightest torrent of gravitational waves that eventually will galaxies p. 46 sweep across the universe. www.Astronomy.com BONUS Vol. 45 OBSERVE WITH MEET THE Why ONLINE • BOTH EYES FILTER GUY CONTENT Issue 11 DARK MATTER WIDE OPEN p. 52 PLUS CODE p. 4 matters p. 30 p. 58 Introducing Meade’s new and improved Coronado SolarMax III Hydrogen – alpha solar telescopes! :4000TT-YLMYHJ[VYLX\PWWLK^P[O! 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Focus Scientific, 911 Carling Ave., Ottawa, Ontario. www.focusscientific.com Ottawa, Ontario, Canada K1J 9G4 613-749-7592 Online Content Code: ASY1711 Enter this code at: www.astronomy.com/code NOVEMBER 2017 to gain access to web-exclusive content VOL. 45, NO. 11 ASTRONOMY DON DIXON FOR FOR DIXON DON ON THE COVER In 2017, a third gravitational wave detection by LIGO revealed the collision and merger of two CONTENTS 24 distant black holes. FEATURES 18 COVER STORY 38 58 COLUMNS Gravitational waves: StarDome and Observe with Strange Universe 10 From novelty to science Path of the Planets both eyes open BOB BERMAN The mergers of at least three RICHARD TALCOTT; Binoculars provide a great way to Observing Basics 14 binary black holes opened a ILLUSTRATIONS BY ROEN KELLY take in lots of sky. And the newest GLENN CHAPLE window into an exotic new realm models have improved the classic of astrophysics. ROBERT NAEYE 44 design. PHIL HARRINGTON Secret Sky 16 Ask Astro STEPHEN JAMES O’MEARA 24 Meteorite origins. 60 Astro Sketching 64 Your guide to the oceans A quick guide to scopes ERIKA RIX of our solar system 46 for kids For Your Consideration 66 Weird, cold, hidden oceans dot Fall into autumn galaxies Gifting the right equipment JEFF HESTER the outer solar system – and Beg, borrow, or steal the doesn’t need to be a daunting Binocular Universe 68 could be sheltering alien life. TOM TRUSOCK biggest scope you can find, task. PHIL HARRINGTON MICHAEL CARROLL and settle in for a great night of deep-sky observing. 62 30 STEPHEN JAMES O’MEARA Get started in video QUANTUM GRAVITY Snapshot 8 Why we need dark matter astronomy Dark matter remains both a 52 Mallincam’s SkyRaider DS2.3 Astro News 12 necessary part of the universe Meet the filter guy Plus is adept at both solar system and a puzzling, unseen How an average Joe turned a and deep-sky video imaging. IN EVERY ISSUE component. FRANCIS REDDY hobby into an astronomy-based JIM THOMPSON business. TEXT AND IMAGES BY From the Editor 6 36 DON GOLDMAN Astro Letters 11 Sky This Month Advertiser Index 71 Venus meets Jupiter. MARTIN RATCLIFFE AND Reader Gallery 72 ALISTER LING Breakthrough 74 Astronomy (ISSN 0091-6358, USPS 531-350) is ONLINE published monthly by Kalmbach Publishing Co., 21027 Crossroads Circle, P. O. Box 1612, Waukesha, WI 53187–1612. Periodicals post- FAVORITES age paid at Waukesha, WI, and additional offices. POSTMASTER: Send address changes to Astronomy, P.O. Box 62320, Tampa, Fla. 33662-2320. Go to www.Astronomy.com Pluto Globe Ask Astro Trips and Picture of Canada Publication Mail Agreement #40010760. for info on the biggest news and Astronomy Archive Tours the Day observing events, stunning photos, presents the Answers to all Travel the world Gorgeous first-ever Pluto your cosmic with the staff of photos from informative videos, and more. globe! questions. Astronomy. our readers. 4 ASTRONOMY • NOVEMBER 2017 Background: IC1396 (Elephant Trunk Nebula) The news so nice, you can read it twice. For the first time ever, Sky-Watcher Esprit’s are Imager: Jerry Gardner on sale throughout October! Designed with the discerning astrophotographer in mind, Scope: Sky-Watcher Esprit 80 EDT f/5 Sky-Watcher USA’s top-of-the-line refractor delivers the kind of imaging performance one would expect from telescopes costing thousands of dollars more. False color is a thing of the past with the Esprit’s apochromatic three-element, air spaced objective lens design. Unlike other refractors, Sky-Watcher USA includes Sky-Watcher USA Esprits come with a 2-element field corrector, guaranteeing a flat field across the entire imaging everything you see here. plane right out of the box. The Sky-Watcher proprietary rack-and-pinion focusing system provides a smooth, rock-solid focuser with zero image shift. 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