Astronomy

CONTENTS

4 ASTRONOMY • JUNE 2018

22 COVER STORY

Water worlds in the
Milky Way
How do planets get their water?
Scientists are looking for
evidence in the light from white
dwarfs. NOLA TAYLOR REDD

28

Exploring Jupiter’s
Trojan asteroids
Astronomers have studied the
giant planet’s captured asteroids
only from afar. But that’s about
to change. JOEL DAVIS

36
Sky This Month
Saturn takes center stage.
MARTIN RATCLIFFE AND
ALISTER LING

38

StarDome and

Path of the Planets

RICHARD TALCOTT;

ILLUSTRATIONS BY ROEN KELLY

44

Astronomy Backstage

Pass: Chicago

his behind-the-scenes tour of

cool astro stuf in the Windy City

includes Adler Planetarium’s

priceless artifacts, incredible

meteorites in the Field Museum,

neutrino detectors at Fermilab,

and the rich history of Yerkes

Observatory. DAVID J. EICHER

52

Discover great galaxies in

Coma Berenices

Spirals, ellipticals, and interacting

galaxies make a rich habitat

for springtime galaxy hunters.

STEPHEN JAMES O’MEARA

58

Three nights at

Pic du Midi

Perched more than 9,400 feet

above sea level, this French

observatory ofers some of

the inest viewing on Earth.

DAMIAN PEACH

64

Astronomy tests

QHYCCD’s new

astrocamera

he 128C ofers full-color

imaging, low noise, and ease

of use. TEXT AND IMAGES BY

TONY HALLAS

70

Ask Astro

he tides on Titan.

COLUMNS

Strange Universe 14

BOB BERMAN

Observing Basics 16

GLENN CHAPLE

For Your Consideration 18

JEFF HESTER

Secret Sky 20

STEPHEN JAMES O’MEARA

Binocular Universe 68

PHIL HARRINGTON

QUANTUM GRAVITY

Snapshot 11

Remembering

Stephen Hawking 12

Astro News 15

IN EVERY ISSUE

From the Editor 6

Astro Letters 8

New Products 66

Advertiser Index 67

Reader Gallery 72

Breakthrough 74

FEATURES

JUNE 2018

VOL. 46, NO. 6

28

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 postage

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

FAVORITES

Go to http://www.Astronomy.com

for info on the biggest news and

observing events, stunning photos,

informative videos, and more.

MARK GARLICK

ON THE COVER

Astronomers are finding watery

worlds orbiting stars around us —

and the way some of those worlds

get their water is surprising.

Dave’s

Universe

The inside

scoop from

the editor.

Venus

Globe

Get the hottest

globe around.

Ask Astro

Archive

Answers to all

your cosmic

questions.

Sky This

Week

A daily digest

of celestial

events.

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