Image: A mysterious glow at the center of the Milky Way. The Chandra X-Ray Observatory lets astronomers see the hidden x-ray radiation of celestial bodies. Credit: NASA.
For the story:
http://www.nasa.gov/vision/universe/...handrahot.html
The Milky Way's Glowing Ghost
06.24.04
If you take a close look at the center of the Milky Way, what will you find?
Plenty of stars, a super-massive black hole, and something new and exciting just discovered using NASA's Chandra X-ray Observatory.
The orbiting telescope has detected a mysterious cloud of extremely hot gas in the heart of the galaxy, and no one's really sure how it got there.
Astronomers at the University of California in Los Angeles took images of the area using Chandra and filtered out all the other possible sources of x-ray radiation: white dwarves, neutron stars and galaxies in the background. What they were left with was a huge amount of x-ray radiation that is most likely emanating from an ultra-hot gas cloud.
"There is no known class of objects that could account for such a large number of high-energy X-ray sources at the galactic center," said Fred Baganoff of the Massachusetts Institute of Technology, co-author of an Astrophysical Journal article on the discovery.
Trying to identify the source of radiation was certainly a great puzzle in itself, but here's the bigger mystery: Why is it still hot? A gas cloud like this one - 18 million degrees Fahrenheit in some parts and 180 million degrees in others - should have cooled off billions of years ago.
There are a couple of leading theories that involve supernovae shockwaves. When the life of a star ends in the dramatic explosion of a supernova, magnetic turbulence and high-energy atomic particles are blasted out into space. Either one of those products could be responsible for heating the gas cloud, but both ideas lead to even more questions. The truth is, no one's really sure how this gas cloud has stayed so hot.
Image: The Chandra X-ray Observatory was deployed into orbit from Space Shuttle Columbia in July of 1999. The telescope is part of NASA's Great Observatories program. Credit: NASA.
Astronomers working on the study aren't even completely sure they're looking at a gas cloud at all. It could be a collection of objects that we've never seen before, combining to create one big glow of x-ray radiation. That's kind of like looking at a city from a distance; all the individual points of light seem to create one giant glow.
However, Michael Muno, astrophysics researcher from UCLA and lead author of the Astrophysical Journal article, is pretty confident he knows what Chandra is looking at.
"The best explanation for the Chandra data is that the high-energy x-rays come from an extremely hot gas cloud," says Muno. "This would mean that there is a significant shortcoming in our understanding of heat sources in the center of our Galaxy."
Keep up-to-date on the latest interstellar x-ray mysteries by visiting the Chandra X-ray Observatory site.
Matthew Cavagnaro, KSC Staff Writer
NASA's John F. Kennedy Space Center and Chandra X-ray Center
A "Ghost" in the Galaxy?
