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Astronomers spot 'fossil' fireballs from supernovae.

Byline: ANI

Washington, January 9 (ANI): Studies of two supernova remnants using the Japan-US Suzaku observatory have revealed never-before-seen embers of the high-temperature fireballs that immediately followed supernovae explosions.

"This is the first evidence of a new type of supernova remnant - one that was heated right after the explosion," said Hiroya Yamaguchi at the Institute of Physical and Chemical Research in Japan.

A supernova remnant usually cools quickly due to rapid expansion following the explosion.

Then, as it sweeps up tenuous interstellar gas over thousands of years, the remnant gradually heats up again.

Capitalizing on the sensitivity of the Suzaku satellite, a team led by Yamaguchi and Midori Ozawa, a graduate student at Kyoto University, detected unusual features in the X-ray spectrum of IC 443, better known to amateur astronomers as the Jellyfish Nebula.

The remnant, which lies some 5,000 light-years away in the constellation Gemini, formed about 4,000 years ago.

The X-ray emission forms a roughly circular patch in the northern part of the visible nebulosity.

Suzaku's X-ray Imaging Spectrometers (XISs) separate X-rays by energy in much the same way as a prism separates light into a rainbow of colors.

This allows astronomers to tease out the types of processes responsible for the radiation.

The team suggests that the supernova occurred in a relatively dense environment, perhaps in a cocoon of the star's own making.

As a massive star ages, it sheds material in the form of an outflow called a stellar wind and creates a cocoon of gas and dust.hen the star explodes, the blast wave traverses the dense cocoon and heats it to temperatures as high as 100 million degrees F (55 million C), or 10,000 times hotter than the sun's surface.

Eventually, the shock wave breaks out into true interstellar space, where the gas density can be as low as a single atom per cubic centimeter - about the volume of a sugar cube.

Once in this low-density environment, the young supernova remnant rapidly expands.

The expansion cools the electrons, but it also thins the remnant's gas so much that collisions between particles become rare events.

Because an atom may take thousands of years to recapture an electron, the Jellyfish Nebula's hottest ions remain even today. (ANI)

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Publication:Asian News International
Date:Jan 10, 2010
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