Image: Cassiopeia A
This view of the supernova remnant Cassiopeia A is the most detailed image ever made of the remains of an exploded star. The green ring marks the location of a shock wave generated by the explosion. A jetlike structure that protrudes beyond the shock wave can be seen at upper left. In the accompanying blue image, processed to highlight silicon ions, a counter-jet is at lower right.
By Senior science writer
updated 8/25/2004 6:42:58 PM ET 2004-08-25T22:42:58

The Chandra X-ray Observatory has re-imaged a familiar scene of a relatively nearby exploded star, revealing new details of the chaotic aftermath.

The supernova remnant, as it is called, is named Cassiopeia A. It is about 10,000 light-years away.

Billowing clouds of superhot gas emanate from the site of the eruption, a star that has since collapsed into a neutron star. It is packed with nothing but neutrons huddled together so tightly that a teaspoonful, if brought to Earth, would weigh more than an elephant.

Chandra first imaged the exploded remains five years ago as its initial target after being launched into orbit. That exposure lasted about 90 minutes. The new photo involved more than 11 days of exposure time.

"Although this young supernova remnant has been intensely studied for years, this deep observation is the most detailed ever made of the remains of an exploded star," said Martin Laming of the Naval Research Laboratory. "It is a gold mine of data that astronomers will be panning through for years to come."

The rich detail has already paid off. Astronomers spotted previously unseen jets of material shooting in opposite directions ahead of the main, expanding cloud of material. The jets reach about 10 light-years from the neutron star.

"The presence of the bipolar jets suggests that jets could be more common in relatively normal supernova explosions than supposed by astronomers," said Una Hwang of NASA's Goddard Space Flight Center.

The new observations also showed that parts of the expanding bubble are rich in iron. Yet the far-reaching jets are rich in silicon and don't contain much iron. The researchers suspect the explosion generated a strong magnetic field that accelerated the high-speed jets. Theorists are not sure how these jets, which can approach the speed of light, are shot from neutron stars and black holes.

A paper on the observations by Hwang, Laming and colleagues will be published in Astrophysical Journal Letters.

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