test 1 Astronomy - May 2018 USA | Page 6

FROM THE EDITOR BY DAV I D J. E I C H E R Editor David J. Eicher Art Director LuAnn Williams Belter How our solar system formed EDITORIAL Managing Editor Kathi Kube Senior Editors Michael E. Bakich, Richard Talcott Associate Editors Alison Klesman, Jake Parks Copy Editors Dave Lee, Elisa R. Neckar Editorial Assistant Amber Jorgenson ART Graphic Designer Kelly Katlaps Illustrator Roen Kelly Production Specialist Jodi Jeranek CONTRIBUTING EDITORS Bob Berman, Adam Block, Glenn F. Chaple, Jr., Martin George, Tony Hallas, Phil Harrington, Korey Haynes, Jeff Hester, Liz Kruesi, Ray Jayawardhana, Alister Ling, Steve Nadis, Stephen James O’Meara, Tom Polakis, Martin Ratcliffe, Mike D. Reynolds, Sheldon Reynolds, Erika Rix, Raymond Shubinski EDITORIAL ADVISORY BOARD O ne of the most fundamental ques- tions we innately have as humans is the simple notion of where we came from. In astronomy, that question can be asked on a variety of scales — where did we as creatures come from? Where did our solar system come from? Our galaxy? he uni- verse at large? This month’s cover story by science journalist Jesse Emspak takes on the ques- tion of the origin of the solar system. For many years, astronomers thought they had a neat answer, with the Sun and its retinue of planets having coalesced from a dusty disk, the debris clear- ing out once our star began nuclear fusion. From there, it was a simple matter of Jupiter dominating the gas giants, by happenstance, and Earth taking on the role as the most massive of the terrestrial planets by pure luck. They also believed that our solar system is typical, and that most solar systems around us ought to resemble ours. Studies over the past few years have upset the apple cart of how our solar system formed and its early history. Emspak’s story tells the sordid tale as it is now shaping up for planetary scientists. The idea that our solar system’s early history must be very different from the con- ventional notion came along suddenly. Fueled by com- puter modeling and by obser- vations made by the Kepler space telescope, the new view of the solar system is radical compared with the old. Scientists now know that protoplanets bounced around the early solar system “like billiard balls,” in Emspak’s words, and that our solar system is very different from most others we see around us. The so-called Late Heavy Bombardment pummeled the inner solar system, and we can still see its effects on the ancient surfaces of Mercury and the Moon. Compared with the mod- els, the real Mars in our solar system is far less mas- sive than astronomers would expect it to be. Scads of small objects like asteroids and Kuiper Belt objects have been scattered into eccen- tric, oddball orbits. Something catastrophic or extremely energetic had to have pushed these bodies Follow the Dave’s Universe blog: www.Astronomy.com/davesuniverse Follow Dave Eicher on Twitter: @deicherstar 6 A ST R O N O M Y • MAY 2018 into their weirdo orbits, and planetary scientists now believe that migration of planets played a major role in the early history of our solar system. Many planetary scientists now believe that Jupiter formed relatively close to the Sun and pushed outward early on, clearing a lane and shoving material outward, as it also left a “tail” of debris in its wake. Saturn then formed, and both plan- ets moved inward in a kind of spirograph wobble, fling- ing other objects inward and outward. After depleting material near them, the two largest planets made their way outward once again. The details of how we got the solar system we have today are incredible. These are still ideas being worked on, but they clearly show that forming the solar sys- tem was a far more compli- cated task than anyone imagined until just a few years ago. Buzz Aldrin, Marcia Bartusiak, Timothy Ferris, Alex Filippenko, Adam Frank, John S. Gallagher lll, Daniel W. E. Green, William K. Hartmann, Paul Hodge, Edward Kolb, Stephen P. Maran, Brian May, S. Alan Stern, James Trefil Kalmbach Publishing Co. CEO Dan Hickey Senior Vice President, Sales & Marketing Daniel R. Lance Vice President, Content Stephen C. George Vice President, Consumer Marketing Nicole McGuire Art and Production Manager Michael Soliday Corporate Advertising Director Ann E. 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