70 Scientific American, December 2019
Chandra was designed to solve a key question in x-ray astronomy:
What is the makeup of the diffuse x-ray light that appears to be present in
every direction of the cosmos—the so-called x-ray background? It was also
designed to be a “general observatory,” with most of the telescope time
awarded to scientists around the world working on diverse projects, cho-
sen after an annual call for proposals. Even after two decades of operation,
Chandra receives around 500 to 650 proposals every year, which amounts
to about 5.5 times more observing time requested than we have to grant—
the process is highly competitive.
Chandra has been extraordinarily productive. It achieved its original
goal by revealing that nearly all of the mysterious x-ray background light
comes from thousands of individual supermassive black holes at the cen-
ters of other galaxies. It also revealed new secrets from a host of celestial
objects: strong x-ray emission from jets of material flying out of supermas-
sive black holes in the process of gobbling up matter; shining aurorae in
the atmosphere around Jupiter; light from colliding neutron stars that
were also detected through gravitational waves; and extremely bright star-
sized black holes aptly named ultraluminous x-ray sources. Science papers
based on Chandra observations number more than 8,000, and our user
community numbers more than 4,000 scientists worldwide.
I joined the mission three years before launch as deputy group leader
for user support. I was involved with building the Web site and documents
to provide information for our scientist users, the first call for proposals
and peer review, and the calibration of the telescope as it was prepared for
launch at nasa’s Marshall Space Flight Center in Alabama. Although this
time was busy and stressful as we pulled everything together for liftoff, it
was nothing compared with the first few months after launch.
Chandra has reached its 20th anniversary year, and the observatory is
still going strong. I serve as director of the Chandra X-ray Center in Cam-
bridge, Mass., where we run the telescope’s operations. With telescopes
coming online now and in the future, such as the Event Horizon Telescope,
the James Webb Space Telescope, and many more, we expect Chandra to
continue to forge new ground and further expand our knowledge of the
hottest and most violent places in the universe for years to come.
S
ince its launch in 1999 , nasa’s chandra X-ray ObservatOry
has been studying the heavens through short-wave-
length x-ray light, the best window for sighting colos-
sal black holes, galaxy clusters and the remnants of
violent supernovae. The telescope captures the posi-
tion, energy and arrival time of each x-ray photon
that reaches its detector. That ability, in combination
with its uniquely sharp imaging quality and capacity to see x-ray
light over a broad range of energies, has revolutionized our view of
the x-ray universe. It has changed our understanding of big myster-
ies such as dark matter, the birth of stars and even the properties of
the planets in our solar system.
IN BRIEF
This year is the 20th
anniversary of nasa’s
Chandra X-ray
Observatory, which
has been continually
orbiting Earth since
its 1999 launch.
The telescope has
made major discov-
eries about super-
massive black holes,
the remnants of
supernova explo-
sions, and more.
As it begins its third
decade, Chandra
continues to be pro-
ductive. Planned col-
laborations with new
and existing obser-
vatories will further
expand our knowl-
edge of the universe.
Belinda J. Wilkes is a senior astrophysicist
at the Smithsonian Astrophysical Observatory
and director of the Chandra X-ray Center, both
in Cambridge, Mass.
© 2019 Scientific American © 2019 Scientific American
