A Stellar Imagemaker

Smithsonian and NASA's Chandra x-ray observatory sheds new light on the mysteries of the universe

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August 19, 1999, Smithsonian’s Chandra X-ray Observatory Center in Cambridge, Massachusetts: a large room full of computers, monitoring equipment and anxious scientists. They were anxious because after many years of hard work, after two scrubbed launches and a near-abort, after seven booster rocket firings joggling the delicate machinery this way and that, their x-ray telescope was finally in orbit and about to open up for business.

“It was quite a scene,” recalled Leon van Speybroeck, one of the men who put it there. “The launch was on the Columbia space shuttle, carrying its biggest payload ever. Now, a month later, we were ready. So, we sent the computer commands, and waited. Astonishingly, 80,000 miles away, our pyrotechnic device exploded — it was like an M-80 firecracker. It swung open the 120-pound door on the spacecraft — just as planned.”

Cosmic x rays shone on the delicate mirrors of the precious telescope for the first time. The scientists back on Earth monitoring the event pulled off their headphones and rushed into the imaging room. For 45 long minutes everyone waited to see if they would get an image from the telescope or if the whole project would end up with “a bucket of broken glass,” as van Speybroeck put it.

Then, in the classic grave space-age monotone, a scientist announced: “We’re getting photons.”

First just a dot on the screen — photons being tiny units of light — then another, and another. Gradually a picture of a distant galaxy emerged.

More than 23 years in the making, mainly at the Smithsonian Astrophysical Observatory in Cambridge, which is part of the Harvard-Smithsonian Center for Astrophysics, and named for the late Nobel laureate Subrahmanyan Chandrasekhar, the Chandra telescope’s first images astounded the sophisticated spacewatchers.

The first official Chandra image shows the aftermath of a vast stellar explosion in Cassiopeia A, a supernova remnant 10,000 light-years away, with such clarity that a neutron star or black hole appears to be visible at its center.

“We see the collision of the debris from the exploded star with the matter around it,” said center director Harvey Tananbaum, describing the image. “We see shock waves rushing into interstellar space at millions of miles per hour, and for the first time a bright point near the center of the remnant that could possibly be a collapsed star.”

Another early x-ray image attesting to Chandra’s power and potential came all the way from a quasar six billion light-years away. Dubbed PKS 0637-752 by scientists, it radiates with the power of ten trillion suns. Complementing the Hubble Space Telescope, another large space observatory now orbiting Earth, Chandra should allow scientists to analyze some of the great mysteries of the universe. For more than a year now, the x-ray telescope has been transmitting a stream of images that have thrilled and challenged the scientific community.

For instance, Chandra’s observation of Sagittarius A*, a source of radio waves at the core of the Milky Way that scientists surmise is powered by a black hole 2.6 million times the mass of our sun, created a stir last winter. With the remarkable detection of an x-ray source from Sag A*, astronomers are closer than ever to clearing up the mystery of the supermassive black hole.


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