Satellite probes secrets of supernovas

GREENBELT, Md., March 20 (UPI) -- U.S. researchers say data from a NASA satellite is providing clues to the elusive origins of an important class of exploding stars called Type Ia supernovas.

These explosions release large and consistent amounts of energy at visible wavelengths that make them among the most valuable tools for measuring distance in the universe.

Because astronomers know the exact brightness of Type Ia supernovas, how bright they appear directly shows how distant they are.

Now X-ray and ultraviolet data from NASA's Swift satellite are helping researchers understand more about them and their processes, a NASA release said Tuesday.

"For all their importance, it's a bit embarrassing for astronomers that we don't know fundamental facts about the environs of these supernovae," Stefan Immler, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Md., said. "Now, thanks to unprecedented X-ray and ultraviolet data from Swift, we have a clearer picture of what's required to blow up these stars."

Astronomers say they believe most Type Ia supernovas start as a white dwarf orbiting a companion star that pulls a stream of matter from it.

As the gas flows onto the white dwarf it gains mass until it reaches a critical threshold and undergoes a catastrophic explosion, they say.

What was unknown was the type of the companion star.

"A missing detail is what types of stars reside in these systems. They may be a mix of stars like the sun or much more massive red- and blue-supergiant stars," researcher Brock Russell of the University of Maryland says.

Studies using Swift data now suggest the companion to the white dwarf is either a smaller, younger star similar to our sun or another white dwarf, researchers say.