Wednesday, September 22, 1999 Published at 11:35 GMT 12:35 UK
Chandra views stellar wreckage
The wreckage of a star that exploded thousands of years ago
By BBC News Online Science Editor Dr David Whitehouse
When a star explodes in a so-called supernova explosion, it can shine as bright as a galaxy of more well-behaved stars. Superhot gas at temperatures of millions of degrees is scattered throughout space.
Sometimes there can be left behind a superdense, small, rapidly-spinning object called a neutron star, which can continue to pump energy into the stellar wreckage.
G21.5-0.9 is about 16,000 light years (1 light year = 10 trillion km/six trillion miles) distant. Chandra's image shows a bright central gas cloud surrounded by a much larger diffuse cloud.
Inside the inner nebula is a bright central source thought to be the rapidly rotating neutron star.
It acts like a powerful generator, creating intense electric voltages that accelerate electrons to speeds close to that of light. Its total output of energy is greater than a thousand Suns.
The appearance of the central nebula is thought to be due to the magnetic field which constrains the motions of the high energy electrons.
"It is a remarkable image," said Dr. Patrick Slane of the Harvard-Smithsonian Center for Astrophysics. "Neither the inner core nor the outer shell has ever been seen before."
Sometimes, spinning neutron stars can give off bursts of radiation like a lighthouse in space. Astronomers call these objects pulsars.
"The Chandra image gives us a much better idea of how this energy source works," said Dr. Stephen Murray, principal investigator for the High Resolution Camera, the X-ray camera used to make PSR 0540-69 image. "You can see X-ray jets blasting out from the pulsar in both directions."
The third new Chandra supernova image is E0102-72. Located in the Small Magellanic Cloud, another satellite galaxy of the Milky Way, E0102-72 is 190,000 light years from Earth.
This object, like G21.5-0.9 and PSR 0540-69, is believed to be the result of a supernova explosion of a massive star several thousand years ago.
"Chandra's gallery of supernova remnants is giving us a lot to think about," said Dr. Fred Seward, of the Harvard-Smithsonian Center for Astrophysics. "We are seeing many things we thought should be there, and many others that we never expected. It is great!"