A supernova's shocking development.

Thirteen years ago, astronomers witnessed the brightest stellar explosion seen from Earth since the invention of the telescope. A supernova--the violent death of a massive star--had erupted in the Large Magellanic Cloud galaxy, only 160,000 light-years away. Because of the galaxy's proximity, scientists have had a field day tracking the unfolding saga of supernova 1987A.

Now, astronomers have for the first time imaged the full force of the shock wave hurled from the supernova. NASA's Chandra X-ray Observatory has detected the gas surrounding the exploded star heated to 10 million kelvins by the shock wave's passage. The speeding wave is plowing into a ring of debris cast out by the star some 20,000 years before it exploded.

The Hubble Space Telescope had previously imaged hot spots in the debris ring, where the shock wave had rammed into it (SN: 2/14/98, p. 100). The hot gas behind the wave, however, emits only X rays, so Hubble can't observe it.

"With Hubble, we hear the whistle from the oncoming train," says David N. Burrows of Pennsylvania State University in State College. "Now, with Chandra, we can see the train." Burrows and his colleagues used Chandra to observe the supernova last October and this past January. Their findings, announced by NASA on May 11, will appear in an upcoming ASTROPHYSICAL JOURNAL.

Even as the shock wave steadily lights up more of the ring, an inward-moving, or reverse, shock will further heat unseen material expelled during the explosion, notes Richard McCray of the University of Colorado at Boulder. "The supernova is digging up its past," he says.