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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
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