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Astronomy Magazine Will a killer asteroid Behind the scenes at the impact Earth? p. 28 Kennedy Space Center p. 44 JULY 2016 The world’s best-selling astronomy magazine NEW RESEARCH Secrets of the Milky Way p. 22 How to observe PLUTO p. 64 www.Astronomy.com PLUS BONUS Vol. 44 TARGET EXPLORE SEEK • our exoplanets ONLINE Issue 7 galaxy’s dark Earth’s big from your CONTENT CODE p. 3 nebulae p. 50 impacts p. 56 backyard p. 60 Spring into a Summer of Spectacular Viewing with 15% off all Tele Vue Eyepieces, Barlows Powermates & Paracorr M24 region imaged by Tony Hallas using a Tele Vue-NP101is refractor. Eyepieces that Make Ethos: 100°-110° Simply spectacular 21, 17, 13, 10, 8, 6, 4.7, 3.7mm Music to Your Eyes! Nagler: 82° The original “spacewalk” —Type 4 Featuring long eye-relief piece of sheet music without a musician to perform it 22, 17, 12mm A is like a telescope image without an eyepiece. The musical notes hang there waiting —Type 5, Featuring largest true fields 31, 26, 16mm to be heard, while a telescope’s image hangs in space waiting to be viewed. Like musi- —Type 6, Featuring compact size cians imparting their own style to music, eyepieces uniquely present a telescope’s view. The 13, 11, 9, 7, 5, 3.5, 2.5mm Delos: 72° Relaxed 20mm eye-relief listener and observer choose the qualities and characteristics they prize most. Selecting 17.3, 14, 12, 10, 8, 6, 4.5, 3.5mm eyepieces becomes a personal journey of what looks and feels right. Panoptic: 68° TFoV Kings in 2” & 1¼” Tele Vue’s eyepiece lines celebrate the differentiation amongst observers. Consistent 41, 35, 27, 24, 19mm is superb image fidelity, stemming from superior optical and mechanical design, glasses, DeLite: 62° Relaxed 20mm eye-relief 18.2, 15, 11, 9, 7, 5mm coatings, manufacturing and 100% quality control. No other eyepieces are as comprehen- Plössl: 50° Refined Plössl performance sively thought-out, manufactured and tested, and as ideal for any type or f/# telescope. 55, 40, 32, 25, 20, 15, 11, 8mm And from May 1st to July 30th, 2016, enjoy a 15% discount from the regularly Nagler Zoom: 50° Unique planetary suggested retail price of all Tele Vue eyepieces, Barlows, Powermates and Paracorr coma 6 to 3mm Continuous Zoom correctors. Call Tele Vue today and let us help you choose the right eyepiece path for you! Paracorr: Perfecting Paraboloids 2” Type 2 , 3” Type 2 Æ Tele Vue 32 Elkay Dr., Chester, New York 10918 (845) 469-4551. televue.com Visionary Online Content Code: ASY1607 Enter this code at: www.astronomy.com/code JULY 2016 to gain access to web-exclusive content VOL. 44, NO. 7 I/AURA) C NASA/ESA/THE HUBBLE HERITAGE TEAM (STS TEAM HERITAGE HUBBLE NASA/ESA/THE ON THE COVER Barred spiral galaxy M83 looks a lot like the Milky Way would from afar, though it’s only about one-third our galaxy’s diameter. It lies about 15 million light-years away in the constellation Hydra. 28 COLUMNS CONTENTS Strange Universe 6 FEATURES BOB BERMAN For Your Consideration 10 22 COVER STORY 38 56 JEFF HESTER The Milky Way StarDome and Explore Earth’s Observing Basics 14 through thick and thin Path of the Planets big impacts GLENN CHAPLE Astronomers studying our gal- RICHARD TALCOTT; Earth has a long history of aster- Secret Sky 18 axy’s vertical structure are teasing ILLUSTRATIONS BY ROEN KELLY oid strikes, and some intriguing STEPHEN JAMES O’MEARA out details about how our home scars remain. MIKE REYNOLDS system evolved. BRUCE DORMINEY 44 Binocular Universe 20 Behind the scenes at 60 PHIL HARRINGTON 28 Kennedy Space Center Seek exoplanets Astro Sketching 66 Falling behind on he home of American from your backyard ERIKA RIX asteroid follow-ups space light is bursting with Learn how amateur astronomers Powerful surveys are discovering memories — and ready to host can help professionals study QUANTUM GRAVITY asteroids at a faster rate than ever the launches of today and worlds outside our solar system. Snapshot 5 before, but most of these Earth- tomorrow. DAVID J. EICHER DENNIS CONTI approaching asteroids never get Astro News 8 a second glance. ILIMA LOOMIS 50 64 Target our galaxy’s The quest for IN EVERY ISSUE 34 dark nebulae distant Pluto From the Editor 4 Ask Astro Pull up a chair, and spend some his newly revealed world at Letters 6, 14, 18, 20 time away from the light. the solar system’s edge makes a New Products 68 36 RICHARD P. WILDS tempting target through amateur The Sky this Month telescopes as it reaches peak Advertiser Index 69 MARTIN RATCLIFFE AND visibility early this summer. Reader Gallery 70 ALISTER LING RICHARD TALCOTT 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 Dave’s Trips & Tours Seasonal Interactive Canada Publication Mail Agreement #40010760. for info on the biggest news and Universe Travel the Observing Star Atlas observing events, stunning photos, The inside world with Find great Pan and zoom scoop from the staff of targets in your through the informative videos, and more. the editor Astronomy summer sky night sky WWW.ASTRONOMY.COM 3 FROM THE EDITOR BY DAVID J. EICHER Editor David J. Eicher Art Director LuAnn Williams Belter EDITORIAL Managing Editor Kathi Kube Senior Editors Michael E. Bakich, Richard Talcott Associate Editor Korey Haynes Copy Editors Dave Lee, Elisa R. Neckar Join us for Editorial Associate Valerie Penton ART Graphic Designer Kelly Katlaps Illustrator Roen Kelly the 2017 Production Coordinator Jodi Jeranek CONTRIBUTING EDITORS Bob Berman, Adam Block, Glenn F. Chaple, Jr., Martin George, Tony Hallas, Phil Harrington, Jeff Hester, Liz Kruesi, Ray Jayawardhana, Alister Ling, Steve Nadis, Stephen James O’Meara, Tom Polakis, Martin Ratcliffe, Mike D. Reynolds, eclipse! Sheldon Reynolds, Erika Rix, Raymond Shubinski EDITORIAL ADVISORY BOARD Buzz Aldrin, Marcia Bartusiak, Timothy Ferris, Alex Filippenko, Adam Frank, John S. Gallagher lll, Daniel W. E. Green, William K. Hartmann, Paul Hodge, Anne L. Kinney, Edward Kolb, The biggest observational we will have a grand time. addition to the eclipse, you’ll Stephen P. Maran, Brian May, S. Alan Stern, James Trefil event in astronomy in a very The first tour, National have ample time to explore long time is fast approach- Parks of the American West, New Orleans and the bayou Kalmbach Publishing Co. ing. On August 21, 2017, the will occur August 13–25, Cajun country and steep in President Charles R. Croft Vice President, Content Stephen C. George Moon will slide across the 2017. This expedition will the traditions of Memphis Senior Vice President, Sales & Marketing Daniel R. Lance Sun’s disk, and a total solar take in the eclipse along with and Nashville. Who could Vice President, Consumer Marketing Nicole McGuire Corporate Art Director Maureen M. Schimmel eclipse will pass diagonally astronomical sights and resist the French Quarter, Art and Production Manager Michael Soliday Corporate Advertising Director Ann E. Smith across the United States. This explorations of great natural Beale Street, the haunts of Single Copy Specialist Kim Redmond will be the first total eclipse beauty. From Scottsdale, Elvis Presley, and the Grand ADVERTISING DEPARTMENT in the continental U.S. in 38 Arizona, the journey will Ole Opry? (888) 558-1544 Advertising Sales Manager Steve Meni years, and the first to cross commence to Sedona, Or think about the third Advertising Sales Representative Dina Johnston, [email protected] both coasts since the closing Arizona; on to Flagstaff with alternative, the Pacific Ad Services Representative days of World War I. a visit to Lowell Observatory; Northwest and San Francisco Christa Burbank, [email protected] The path of totality will Glen Canyon Dam and the trip. 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