ATLANTA, Jan. 12 (Reuters) - Thousands of exploding stars left a telltale halo of searingly hot gas around the Milky Way, NASA scientists reported.
Astronomers have long known about the massive gas halo, but not its cause. Before this, some believed it might have been caused by ultraviolet radiation from hot stars.
But scientists working with the new Far Ultraviolet Spectroscopic Explorer (FUSE) spacecraft determined that hot stars could not produce the atomic remnants they observed in the halo. Only exploding stars could do that, NASA reported at the annual meeting of the American Astronomical Society in Atlanta.
The football-shaped halo is huge, extending about 5,000 to 10,000 light-years above and below the plane of the Milky Way galaxy, which contains Earth. A light-year is about 6 trillion miles (10 trillion kilometers).
FUSE made the discovery by detecting lots of oxygen VI -- oxygen atoms with five of their eight surrounding electrons stripped off -- in the halo.
"The only way to make the observed amount of oxygen VI is through collision with the blast waves from exploding stars, called supernovae,'' Blair Savage of the University of Wisconsin in Madison, a FUSE scientist, said in a statement.
FUSE is just ending its shakedown period after a June 1999 launch, but NASA scientists declared it "open for business."
Starting this year, FUSE is expected to start studying deuterium, a fossil atom left over from the astronomical Big Bang that astronomers believe gave birth to the universe billions of years ago.
FUSE works by looking at the cosmic gas between stars and determining its composition, velocity and distance in relation to bright celestial objects farther away. FUSE is at least 100 times more powerful than previous instruments, which means it can detect new atomic and molecular features.
The ultraviolet light that FUSE observes is invisible to humans.
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