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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. 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