Astronomy

CONTENTS

4 ASTRONOMY • MAY 2018

22 COVER STORY

New insights into how
the solar system formed
Recent observations reveal that
chaos and mayhem ruled our
planetary system’s irst days.
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 JOHNSONGROH

36
Sky This Month
Jupiter shines brilliantly.
MARTIN RATCLIFFE AND
ALISTER LING

38

StarDome and

Path of the Planets

RICHARD TALCOTT;

ILLUSTRATIONS BY ROEN KELLY

44

Ask Astro

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

58

Observe Mars at its best

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.

MICHAEL E. BAKICH

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

Lots of accessories make the

RunCam Night Eagle an easy

match for any telescope or

camera lens. RICHARD P. WILDS

COLUMNS

Strange Universe 10

BOB BERMAN

Secret Sky 14

STEPHEN JAMES O’MEARA

For Your Consideration 16

JEFF HESTER

Binocular Universe 18

PHIL HARRINGTON

Observing Basics 70

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

FEATURES

MAY 2018

VOL. 46, NO. 5

30

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.

ONLINE

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Go to http://www.Astronomy.com

for info on the biggest news and

observing events, stunning photos,

informative videos, and more.

RON MILLER FOR

ASTRONOMY

ON THE COVER

For years, planetary scientists

thought our solar system formed

in a simple way. Now the picture

is more complex.

Trips and

To u r s

Travel the world

with the staff of

Astronomy.

Sky This

Week

A daily digest of

celestial events.

Picture of

the Day

Gorgeous

photos from

our readers.

News

The latest

updates from

the science and

the hobby.

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