Astronomy (USA) 2020-07 Special Issue - All About Stars.pdf

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SPECIAL ISSUE
JULY 2020
The world’s best-selling astronomy magazine
ALL ABOUT
STARS
How stars are born
and die
p. 16
Meet the most
extreme stars
p. 24
The nearest stars
up close
p. 30
The Sun’s lost
siblings
p. 44
How pulsating stars
unlock the cosmos
p. 56
www.Astronomy.com
AND MORE!
Bob Berman’s tribute to carbon
p. 14
Astronomy’s
editors answer your questions
p. 70
BONUS
ONLINE
CONTENT
CODE
p. 4
Vol. 48
•
Issue 7
Online Content Code: ASY2007
Enter this code at:
www.astronomy.com/code
to gain access to web-exclusive content
JULY 2020
VOL. 48, NO. 7
CFHT/COELUM – J.-C. CUILLANDRE & G. ANSELMI
ON THE COVER
CONTENTS
FEATURES
16
How stars are
born and die
Stellar evolution is a circle
of life — dying stars spew
their contents into the galaxy,
paving the way for the next
generation.
JIM KALER
16
Giant spheres of stars, globular
clusters like M15 in Pegasus
contain aged suns that winked
on during the early days of the
universe.
COLUMNS
Strange Universe
14
BOB BERMAN
36
Sky This Month
Feast on a full planetary
lineup.
MARTIN RATCLIFFE
AND ALISTER LING
50
Secret Sky
62
STEPHEN JAMES O’MEARA
Is Eta Corvi a window
to our past?
By studying this strange
star, astronomers hope to
better understand what
happened early in the life
of our own solar system.
NOLA TAYLOR REDD
For Your Consideration
64
JEFF HESTER
Observing Basics
66
GLENN CHAPLE
38
24
Star Dome and
Paths of the Planets
RICHARD TALCOTT;
ILLUSTRATIONS BY ROEN KELLY
Binocular Universe
68
PHIL HARRINGTON
Meet the most
extreme stars
Some huge, some small. Some
zip, some crawl. The cosmos
is full of objects that defy
expectations.
JAKE PARKS
56
7
QUANTUM GRAVITY
Everything you need to
know about the universe
this month: growing
space salads, 139 minor
planets found, and more.
44
The Sun’s lost siblings
Astronomers think it’s possible
to identify the stars that
formed from the same nebula
as the Sun.
YVETTE CENDES
How pulsating stars
unlock our universe
RR Lyrae variables allow
precise distance measurements,
reveal the history of the
regions they populate,
and trace how galaxies are
structured.
ATA SARAJEDINI
30
Stellar neighbors
close-up
Astronomers are learning
a lot from the stars in our
part of the Milky Way.
BRUCE DORMINEY
70
IN EVERY ISSUE
From the Editor
5
Astro Letters
6
Advertiser Index
65
New Products
69
Reader Gallery
72
Breakthrough
74
News
The latest
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and the hobby.
Astronomy
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4
ASTRONOMY
•
JULY 2020
FROM THE EDITOR
What we owe stars
I hope that every day, at least for a
moment, you think of the Sun —
not necessarily because you’re a
solar observer, but out of gratitude. If not for
the Sun, of course, none of us would be here.
Circumstances in our solar system’s forma-
tion and evolution led to Earth being in the
right place to receive enough solar radiation
to permit water, and, thus, life. Our local
nuclear reactor in the sky gives us our exis-
tence, and we owe our lives to it.
The subject of stars is a pretty fundamen-
tal one in astronomy. After all, stars are
practically everywhere when we look up in the sky; galaxies are filled
with them, and the universe is filled with galaxies. It’s a little funny
thinking back over conversations with astronomers and appreciating
how relatively few are actively researching fundamental properties
of stars, given how important stars are to the story of the cosmos. But
enough are studying how stars work that our collective store of knowl-
edge about them is growing.
This special issue presents a pretty impressive tale of what we know.
We’re fortunate to have the dean of writers about stars for a popular
audience, Jim Kaler, now an emeritus professor at the University of
Illinois, kicking off our package with a story about how stars are born
and die. Their life cycles tell us a great deal about how the universe
works and about the past and future of our own solar system.
Associate Editor Jake Parks takes us on a journey through stellar
extremes — the largest, smallest, brightest, and so on — an always-
fascinating and ever-changing tapestry of understanding of these
cosmic engines. Science writer Bruce Dorminey helps us visit the
nearest stars, from the Alpha Centauri system and beyond, in a fas-
cinating look at our galactic neighborhood.
Some 4.6 billion years ago, the Sun was born in an open cluster.
Now it is a single star. What happened to its sisters? Radio astronomer
Yvette Cendes describes the ongoing research on the Sun’s lost siblings,
a detective story spanning years and looking back on a nearly infinite
time span. Science writer Nola Taylor Redd examines the weird star
Eta Corvi, which hides some strange behavioral secrets that could shed
light on many other stars. And physics professor Ata Sarajedini
describes a class known as RR Lyrae stars, one of the tools in an
astronomer’s box that allows us to gauge distances in the cosmos.
I hope you’ll enjoy this special package — and that you’ll continue
to think of the Sun, and give it an occasional wink of appreciation.
Yours truly,
Follow the
Dave’s Universe blog:
www.Astronomy.
com/davesuniverse
Editor
David J. Eicher
Design Director
LuAnn Williams Belter
EDITORIAL
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Phil Harrington, Korey Haynes, Jeff Hester, Alister Ling,
Stephen James O’Meara, Martin Ratcliffe, Raymond Shubinski
SCIENCE GROUP
Executive Editor
Becky Lang
EDITORIAL ADVISORY BOARD
The Sun, our star,
appears like a giant
glowing ball of
radiation in this
image from the
Solar Dynamics
Observatory. As the
universe’s natural
nuclear reactors,
stars tell us an
enormous amount
about how the
universe works.
NASA/SDO
Buzz Aldrin, Marcia Bartusiak, Jim Bell, 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
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