Friday, February 19, 2010

NASA astronomers loosen secret of the supernova

Supernovas have long been used as “cosmic mile markers” to measure the growth of the universe, but NASA scientists now claim that they have finally exposed what actually sparks the massive stellar explosions.

A team of astronomers led by Marat Gilfanov used NASA’s Chandra X-Ray laboratory to study supernovas in five near elliptical galaxies and the central region of the Andromeda galaxy — a spiral galaxy nearby to our own, the Milky Way.

They found that most Type 1a supernovas are sparked by the merging of two white dwarf stars, or the collapsed remains of old stars. The stars become uneven when they exceed their weight limit which causes a stellar explosion, the Telegraph reported.

It was a major discomfiture that we did not know how they (supernovas) worked. Now we are beginning to appreciate what lights the fuse of these explosions, said Gilfanov, an astronomer from the Max Planck Institute for Astrophysics in Germany.

Previously it was consideration that Type 1a supernovas were also caused by accretion — when the gravity of a star draws in enough material from a sun-like companion and becomes unstable.
Though, Akos Bogdan of the Max Planck Institute said: If the supernovas were formed by accretion, the galaxies would be roughly 50 times brighter in x-rays than actually observed.

It is not clear whether merging is also the primary source of supernovas in spiral galaxies, and further study is required, he said. Pairs of white dwarfs are tremendously difficult to find. Once the white dwarfs spiral into expanses when they are about to merge, it takes just a few tenths of a second for them to explode.

The study is available in the latest edition of the journal Nature.

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