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Explorethe Impact That Killed the Dinosaursp. 26 EXPLORE the impact that killed the dinosaurs p. 26 DECEMBER 2016 The world’s best-selling astronomy magazine Understanding cannibal star systems p. 20 How moon dust will put a ring around Mars p. 46 Discover colorful star clusters p. 32 www.Astronomy.com AND MORE BONUS Vol. 44 Astronomy on Tap becomes a hit p. 58 ONLINE • CONTENT Issue 12 Meet the master of stellar vistas p. 52 CODE p. 3 iOptron’s new mount tested p. 62 ÛiÃÌÊÊÞÕÀÊiÞiÌ°°° ...and share the dividends for a lifetime. Tele Vue APO refractors earn a high yield of happy owners. 35 years of hand-building scopes with care and dedication is why we see comments like: “Thanks to all at Tele Vue for such wonderful products.” The care that goes into building every Tele Vue telescope is evident from the first time you focus an image. What goes unseen are the hours of work that led to that moment. 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COLUMNS 26 Strange Universe 10 CONTENTS BOB BERMAN For Your Consideration 14 FEATURES JEFF HESTER Secret Sky 18 20 COVER STORY 36 52 STEPHEN JAMES O’MEARA When galaxies Sky This Month Meet the master Observing Basics 65 Inner planet convention. MARTIN become cannibals of stellar vistas GLENN CHAPLE Some galaxies harbor a sinister RATCLIFFE AND ALISTER LING How I took the astroimaging secret: They’ve eaten their siblings. road less traveled. TEXT AND Astro Sketching 66 MICHAEL WEST 38 IMAGES BY ROGELIO BERNAL ERIKA RIX StarDome and ANDREO Binocular Universe 68 26 Path of the Planets PHIL HARRINGTON Explore the impact that RICHARD TALCOTT; 58 killed the dinosaurs ILLUSTRATIONS BY ROEN KELLY I’ll have a Cosmo QUANTUM GRAVITY As scientists drill into Mexico’s By combining science with a few Chicxulub crater, they expose 44 stellar brews, Astronomy on Tap Snapshot 7 geologic clues about the massive Ask Astro has become a hit. LIZ KRUESI Astro News 8 impact that transformed Earth. 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