NASA’s Chandra X-ray telescope celebrates 20 years in space

The spacecraft launched in July 1999 and has been searching the sky ever since

Chandra images

LOOKING AROUND NASA released a set of images from the Chandra X-ray Observatory to celebrate its 20th anniversary, showing merging galaxies and a supernova remnant, among others.


In July 1999, NASA’s Chandra X-ray Observatory took off aboard the space shuttle Columbia to scan the sky in a wavelength of light invisible to human eyes. For the last 20 years, Chandra has done just that, taking in high-energy X-rays, which can be detected only from above Earth’s atmosphere.

“Chandra remains peerless in its ability to find and study X-ray sources,” said Chandra X-ray Center director and astrophysicist Belinda Wilkes in a statement. “Since virtually every astronomical source emits X-rays, we need a telescope like Chandra to fully view and understand our universe.”

One of the spacecraft’s first images, released August 26, 1999, revealed X-rays from a neutron star or black hole at the heart of Cassiopeia A, the remains of an exploded star found about 11,000 light-years away from Earth (SN: 9/4/99, p. 148).

Chandra first images
LOOKING BACK . The first images that Chandra took were of X-rays from a distant supermassive black hole in galaxy PKS 0637-72 that seems to be spewing a powerful X-ray jet (left) and from the supernova remnant Cassiopeia A (right).NASA, Chandra Science Center

Since then, Chandra has spied on cosmic objects as diverse as merging galaxy clusters in the distant universe, black holes in the center of the Milky Way and the planet next door, Venus (SN: 12/8/01, p. 357). Some of the phenomena Chandra investigates today weren’t even known yet when the telescope launched, such as X-rays emitted in the aftermath of clashing neutron stars that also emitted gravitational waves (SN: 2/17/18, p. 17).

To celebrate the observatory’s 20th anniversary, NASA has released six images highlighting the breadth of what X-rays can reveal. Those images, which show X-ray data combined with optical and other types of observations, include regions where stars are born and the aftermath of their deaths, colliding galaxy clusters and the home of a supermassive black hole.

The first row of the top image above, from left to right, shows Abell 2146 (the result of a collision and merger of two massive galaxy clusters), the region around the supermassive black hole at the center of the Milky Way, and 30 Doradus, a star-forming region located close to the Milky Way.

In the second row of the top image, from left to right, is a cluster of massive and violent stars called Cygnus OB2, a star-forming region called NGC 604 in the nearby galaxy Messier 33, and a supernova remnant called G292.

Lisa Grossman is the astronomy writer. She has a degree in astronomy from Cornell University and a graduate certificate in science writing from University of California, Santa Cruz. She lives near Boston.

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