Supernovae are the evolutionary endpoints for massive stars. Once their fuel is used up, the stars contract and then rebound, spewing material into space in an explosive burst of matter and energy that can briefly outshine an entire galaxy. The new photo shows supernova Cassiopeia A, called Cas A by astronomers. It is 10,000 light-years away. Light from its explosion first reached Earth in the late 1600s, and astronomers have been monitoring it ever since.

The new photo shows the upper portion of the expanding debris field, known as a supernova remnant. Near the top are clumps of cooling matter. Each clump is more than 10 times diameter of our solar system. Over time, astronomers say, a clump will condense under its own weight and compress into a sphere dense enough to jumpstart thermonuclear fusion. A star will be born.

"For years, all anyone saw of the remnant's debris was fuzzy looking clumps and filaments," said Robert Fesen, a Dartmouth College researcher who led the observation. "But with the Hubble images, we were able to show that the supernova debris is actually quite knotty down to the limit of Hubble's resolution."

The exact process by which a supernova rips through space is not completely understood, Fesen said. Some stars seem to blow up spherically, while with others energy is channeled into two jets that head in opposite directions along a star's axis of rotation.

"The upper-left portion of Cas A's debris shell does indeed shows evidence for a breakout maybe caused by a plume of ejected debris," Fesen told SPACE.com. "This lends some support to the jet-explosion model.

More study of the chemical distribution of the ejected material and the motions of the debris structure is needed before conclusions can be reached, he said.

One nice feature about cosmic fireworks: They last a lot longer than the kind shot up from river barges or set off in backyards around the country. The new image, in fact, involves 14 hours of exposure time with Hubble's Wide Field and Planetary Camera 2. Some of it was recorded in January 2000, while the rest was collected in January of this year. Astronomers often combine precious observing time granted months or years apart to create more refined and useful images.

Fesen and his colleagues first published their findings detailing the knotty structures in Cas A last year.

The image released today contains more detail, he said. Colors highlight parts of the debris where chemical elements are glowing. The dark blue fragments, for example, are richest in oxygen. The red material is rich in sulfur. Green areas were originally recorded as orange-red but recolored to visually separate them.

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