Astronomy

CONTENTS

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4 ASTRONOMY • APRIL 2018

22 COVER STORY

Dark matter’s shadowy
effect on Earth
Earth’s periodic passage
through the galaxy’s disk could
initiate a series of events that
ultimately lead to geological
cataclysms and mass extinctions.
MICHAEL R. RAMPINO

28
Sharing the skies
above Chile
The Astronomy in Chile Educator
Ambassadors Program explores
the unique collaboration forged
by U.S. astronomy observatories
in Chile. ALISON KLESMAN

34
Ask Astro
Planet or moon?

36
Sky This Month
Mars and Saturn rendezvous.
MARTIN RATCLIFFE AND
ALISTER LING

38

StarDome and

Path of the Planets

RICHARD TALCOTT;

ILLUSTRATIONS BY ROEN KELLY

44

How supernovae

have affected life

A nearby exploding star may

affect Earth in ways we’re just

now beginning to understand.

ADRIAN L. MELOTT

50

Secrets of nightscape

photography

Get started on this wonderfully

challenging marriage of artistic

vision, nocturnal exploration,

and technical sophistication.

TEXT AND IMAGES BY

STEVE CULLEN

56

The story of PlaneWave

This innovative company isn’t

just about optics — the key is

its people. TEXT AND IMAGES BY

TONY HALLAS

59

Spring’s best

& brightest galaxies

Galaxies in and around Virgo

offer a telescopic delight for

deep-sky fans. PHIL HARRINGTON

64

Binoculars made for

the night sky

These 10x70 binoculars

offer high-quality glass,

rugged construction, and

great low-light performance.

RAYMOND SHUBINSKI

COLUMNS

Strange Universe 10

BOB BERMAN

Secret Sky 16

STEPHEN JAMES O’MEARA

For Your Consideration 18

JEFF HESTER

Binocular Universe 68

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 66

Advertiser Index 67

Reader Gallery 72

Breakthrough 74

FEATURES

APRIL 2018

VOL. 46, NO. 4

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 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

FAVORITES

Go to http://www.Astronomy.com

for info on the biggest news and

observing events, stunning photos,

informative videos, and more.

DON DIXON FOR

ASTRONOMY

ON THE COVER

Our solar system periodically

passes through the Milky Way’s

disk. Could the galaxy’s dark

matter cause harm to Earth?

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