test 1 Astronomy - May 2018 USA | Page 4

Online Content Code: ASY1805 Enter this code at: www.astronomy.com/code to gain access to web-exclusive content MAY 2018 VOL. 46, NO. 5 CONTENTS ON THE COVER 30 For years, planetary scientists thought our solar system formed in a simple way. Now the picture is more complex. FEATURES 22 COVER STORY New insights into how the solar system formed 38 StarDome and Path of the Planets Recent observations reveal that chaos and mayhem ruled our planetary system’s irst days. RICHARD TALCOTT; ILLUSTRATIONS BY ROEN KELLY JESSE EMSPAK 28 An organically grown planet definition Should we really deine a word by voting? KIRBY D. RUNYON AND S. ALAN STERN 30 Seeking the unknown in cosmic data In an era of large-scale surveys, citizen science projects, and new machine-learning techniques, unexpected discoveries should be expected. MARA JOHNSON-GROH 36 Sky This Month COLUMNS Strange Universe 10 BOB BERMAN Secret Sky 14 44 Ask Astro 58 Observe Mars at its best Black hole jets. 46 Why do galaxies align? he matter in our universe forms ilaments and threads like a grand cosmic web, tugging galaxies and clusters into place along the way. MICHAEL WEST 52 Leo’s exotic deep-sky gems Beyond the brightest galaxies, the Lion contains many challenging deep-sky targets. STEPHEN JAMES O’MEARA Jupiter shines brilliantly. Binocular Universe 18 MICHAEL E. BAKICH Observing Basics 70 62 Guide your camera to great shots A variety of mounts and techniques can help you create stunning images. Which one is for you? MIKE REYNOLDS 66 Capture video with this low-cost camera ONLINE FAVORITES Go to www.Astronomy.com for info on the biggest news and observing events, stunning photos, informative videos, and more. 4 A ST R O N O M Y • MAY 2018 For Your Consideration 16 It’s been 15 years since the Red Planet was this close and this big. Set up your scope, and take advantage of this apparition. Lots of accessories make the RunCam Night Eagle an easy match for any telescope or camera lens. RICHARD P. WILDS MARTIN RATCLIFFE AND ALISTER LING STEPHEN JAMES O’MEARA Trips and Tours Sky This Week Picture of the Day Travel the world with the staff of Astronomy. A daily digest of celestial events. Gorgeous photos from our readers. News The latest updates from the science and the hobby. JEFF HESTER PHIL HARRINGTON GLENN CHAPLE QUANTUM GRAVITY Snapshot 8 Astro News 12 IN EVERY ISSUE From the Editor 6 Astro Letters 11 New Products 68 Advertiser Index 69 Reader Gallery 72 Breakthrough 74 Astronomy (ISSN 0091-6358, USPS 531-350) is published monthly by Kalmbach Publishing Co., 21027 Crossroads Circle, P. O. Box 1612, Waukesha, WI 53187–1612. Periodicals post- age paid at Waukesha, WI, and additional offices. POSTMASTER: Send address changes to Astronomy, P.O. Box 62320, Tampa, Fla. 33662-2320. Canada Publication Mail Agreement #40010760.