Sky and Telescope - August 2017 - 57

BOOK REVIEW by S. N. Johnson-Roehr

X-Ray Revelations

CHANDRA'S COSMOS: Dark Matter, Black Holes, and Other Wonders
Revealed by NASA's Premier X-Ray Observatory

Wallace H. Tucker
Smithsonian Books, 2017
272 pages, ISBN 978-1-58834-587-5
$29.95, hardcover.

LIKE MOST visual observers, I don't

spend a lot of time thinking about
X-rays when I'm at the eyepiece. Give
me a telescope, a deep-sky atlas, and an
O III ﬁlter, and I'm usually good for the
night. But when Chandra's Cosmos: Dark
Matter, Black Holes, and Other Wonders Revealed by NASA's Premier X-Ray
Observatory landed on my desk, I picked
it up immediately, hoping I would learn
a thing or two. Good news: I didn't just
learn a thing or two - I learned a lot.
You may already be familiar with the
basics of the Chandra X-Ray Observatory, a space telescope launched by NASA
in July 1999 to study the high-energy
X-ray universe. Chandra's working life
began after its deployment from the
space shuttle Columbia into an orbit
some 86,500 miles above the Earth.
(Space telescopes enable astronomers

to detect wavelengths that never make
it through Earth's atmosphere.) Since
ﬁrst light - NASA released Chandra's
ﬁrst images of the supernova remnant
Cassiopeia A on August 26, 1999 -
Chandra has functioned as a "cosmic
X-ray machine," gathering observational
data in the form of high-resolution X-ray
images of the hottest regions of our
universe, such as galaxy clusters, black
holes, and supernovae. Chandra's images
supplement those we receive from other
space telescopes (most notably the
Hubble Space Telescope, which observes
near-infrared, optical, and ultraviolet
radiation, and the Spitzer Space Telescope, which observes in the infrared).
Adding X-ray data to the picture gives
astronomers a more complete vision of
the universe, allowing them to model
our past and future more accurately.
In Chandra's Cosmos, Wallace H.
Tucker, Science Spokesperson for the
Chandra X-Ray Center at the Smithsonian's Astrophysical Observatory,
takes on the tremendous task of
interpreting the X-ray universe for the
layperson. It's not an easy or enviable job. For instance, to interpret an
X-ray image of the galaxy cluster Abell
383 for the reader, ﬁrst Tucker has to
explain dark matter (hot, cold, and
warm), dark energy, and competing
theories of gravity (Einstein is still the
best thing going). To clarify Chandra's
contributions to the study of supernovae remnants, parts of which are only
detectable in the X-ray, Tucker has to
ﬁrst walk the reader through a course in
stellar chemistry and nuclear physics.
Sound complicated? It is. But luckily,
the combination of Tucker's lucid prose
and Chandra's high-resolution imagery
makes it seem less so. I admit: I had to

read some of the dark matter discussion a few times over, and the physics of
black holes can be truly mind-blowing,
but the deeper I got in the book, the
more it all made sense.
Tucker groups Chandra's triumphs
under three headings: The Big (think
cosmology, especially questions of dark
matter and dark energy); The Bad (black
holes, Seyfert galaxies, and quasars); and
The Beautiful (supernovae, their remnants, and neutron stars). Each section
focuses on a big question in astronomy
(How does a black hole merger happen?
How do stars die?) and includes a "reading" of Chandra images that astronomers use as part of their answer. I appreciated the inclusion of the controversies
and the arguments. Tucker frequently
leads with the most accepted solution to
a problem but includes evidence from its
detractors as well.
Chandra's Cosmos is an attractive volume with illustrations weighted toward
the purple end of things, as you might
expect from a book on X-ray astronomy.
Tucker decodes each image, sometimes using supplemental diagrams,
to explain what we're seeing and show
how astronomers are using the colorful
data. Initially, the matte ﬁnish of the
pages disappointed me, but once I began
following Tucker's arguments through
the images, I began to appreciate the
book's resilience to ﬁngerprints.
If you have a quiet space nearby and
a little time for thinking, don't hesitate
to pick up Chandra's Cosmos. This is one
book that will change the way you see
our universe.
¢ Observing Editor S. N. JOHNSONROEHR likes her astronomy to stretch
across the electromagnetic spectrum.
s k y a n d t e l e s c o p e .c o m

* AUGUST 2017

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Sky and Telescope - August 2017

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