SPACE.com -- First Sign of Impending Stellar Catastrophe

In a composite view of the Crescent Nebula, X-ray readings are blue and optical data is shown as red and green.

For context, this composite image shows the portion of the Crescent Nebula, as a square, covered by the new Chandra observation. The star fueling all the beauty is to the lower right of the square.

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	First Sign of Impending Stellar Catastrophe By SPACE.com Staff posted: 07:00 am ET 15 October 2003

For Wednesday HP

The Chandra X-ray Observatory has captured a "shocking" scene that astronomers say shows the first signs of a total stellar explosion in the making.

The star, named HD 192163, is massive and like all heavyweights will not live long. After 4.5 million years -- just one-thousandth the current age of the Sun -- HD 192163 is already rushing headlong toward a supernova explosion that could occur about 100,000 years from now, astronomers said yesterday.

Before it blows, though, HD 192163 is beautifying space.

This new picture is of a portion of the Crescent Nebula, a giant gaseous shell created by powerful winds blowing from the massive star, which is out of the field of view to the lower right. It's a composite image, with X-ray readings in blue and optical data shown in red and green.

The initial steps to oblivion involved some expansion. HD 192163 grew to become a red giant and ejected its outer layers at about 20,000 mph. Some 200,000 years later -- a blink of the eye in the life of a normal star -- the intense radiation from the exposed hot, inner layer of the star began pushing gas away at speeds in excess of 3 million mph.

When this high speed "stellar wind" rammed into the slower red giant wind that had been sent out previously, a dense shell formed. In the image, a portion of the shell is shown in red. The force of the collision created two shock waves: one that moved outward from the dense shell to create the green filamentary structure, and one that moved inward to produce a bubble of million degree Celsius X-ray emitting gas (blue).

The brightest X-ray emission is near the densest part of the compressed shell of gas, indicating that the hot gas is evaporating matter from the shell.

HD 192163 is a Wolf-Rayet star, and also goes by the name WR 136. The surrounding Crescent Nebula has been photographed also by the National Science Foundation's 0.9-meter telescope on Kitt Peak in Arizona, as well as by the Hubble Space Telescope.

The new Chandra image will help researchers determine the mass, energy, and composition of the gaseous shell around this pre-supernova star. An understanding of such environments provides important data for interpreting observations of supernovas and their remnants.

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