X-ray Explorers20 AUGUST 2019 • SKY & TELESCOPEthe aspect operations scientist, who looked up the source and
discovered that a radio image showed an extension in the
same direction. Chandra was simply imaging the powerful jet
emanating from near the black hole.
“We went to point at another source... and it also had
a jet!” Tananbaum says, laughing. The widespread existence
of X-ray-emitting jets highlights Chandra’s capabilities, Elvis
notes: “Einstein showed that everything is an X-ray source;
Chandra showed that pretty much everything is extended.”
Meanwhile, the three X-ray telescopes onboard XMM-
Newton have collected an abundance of photons from hun-
dreds of thousands of sources, providing energy information
that’s crucial to interpreting the science. Together, Chandra
and XMM-Newton have revolutionized the fi eld once more.Curse of the Calorimeter
One instrument that could explore the X-ray spectrum —
but hasn’t yet — is a microcalorimeter. By recording the min-
ute changes in heat due to incoming
X-ray photons, this instrument would
act as an extremely sensitive and
high-resolution spectrometer unlike
any fl own so far.
A microcalorimeter could help
astronomers understand what sus-
tains galaxy clusters against collapse
or dissolution, and it could measure
the elements and energy supernovae
distribute throughout the universe. It
could also help solve a key cosmological
mystery: the case of the missing matter.
Dark matter aside, astronomers can’t
even account for all normal matter in
their observations of stars, dust, and
gas. Tentative fi ndings from Chandra and XMM-Newton
suggest that this missing mass might lurk as hot, tenuous gas
between galaxies. But the needed measurements are exceed-
ingly diffi cult to make with current instruments.
A microcalorimeter originally intended to accompany
Chandra into space was bumped to another mission, which
was later cancelled. In 2000 a more advanced version of that
instrument fl ew on the Japanese Astro E mission, but therocket carrying it exploded shortly after launch. A replace-
ment was fl own on Astro E2, later christened Suzaku, but
that too failed: A mistake in communication led to a design
fl aw that boiled away the cryogen required to keep the instru-
ment cool, rendering it useless before the instrument could
take a single observation.
The next project, called Hitomi (Japanese for “pupil of
the eye”), integrated a lot of changes, including advances
to the instrument itself and improvements in communica-
tions. “They decided to be paranoid,” says Ann Hornsche-
meier (NASA Goddard Space Flight Center). Before all the
instruments were deployed or even the (transparent) shutter
opened, the Hitomi team
took promising observa-
tions of hot gas drifting in
the Perseus galaxy cluster.
“But I don’t think any-
body would have guessed
that that would be the end
of the mission,” Horn-
schemeier adds.
On March 26, 2016,
a series of minor errorspTYCHO Einstein could resolve turbulent structures, such as in the re-
mains of a Type Ia supernova that appeared in Cassiopeia in 1572 (inset).
Chandra later captured far fi ner detail within the Tycho remnant.pUNEXPECTED JET
Chandra revealed a
jet extending sev-
eral hundred thousand
light-years from the
distant quasar PKS
0637–752.uPULSAR IN ANDROMEDA
XMM-Newton spotted the fi rst
known pulsar spinning in our
sister galaxy.2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 20Kvant
High Energy Transient Explorer (HETE) 2IntegralNeil Gehrels Swift ObservatorySuzaku (Astro E2)AGILEAlexis
RXTE
IRS P3
BeppoSAX
ChandraXMM-NewtonARGOS
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