Wednesday, May 26, 2010

A New Kind of Supernova

Scientists believe they have discovered a supernova that was caused in a way not previously know. Before the discovery there were thought to be two ways that supernovas formed. Supernova SN2005E appears not to have been created in either of those ways. It has become something of a mystery as to what could cause it. The leading theory involves two close white dwarves one stealing helium from the other until reaching a critical detonation point.

"Not all supernovae are created equal, astronomers are finding. A faint supernovae found by international teams of scientists is like nothing previously seen, and cannot be explained by conventional insights into these exploding stars. Until now, only two basic kinds of supernovae had been observed. But now there appears to be a third.
The first two types of supernova are either hot, young giants that go out in a violent display as they collapse under their own weight, or old, dense white dwarves that blow up in a thermonuclear explosion.
SN2005E was first spotted on January 13, 2005 in the nearby galaxy NGC1032, and since then scientists have carried out various observations of it using different telescopes.

On the one hand, the amount of material hurled out from the supernova was too small for it to have come from an exploding giant. In addition, its location, distant from the busy hubs where new stars form, implied it was an older star that had had time to wander off from its birthplace. On the other hand, its chemical makeup didn't match that commonly seen in the second type.

"It was clear," said lead author Hagai Perets from the Weizmann Institute in Israel and the Harvard-Smithsonian Center for Astrophysics, "that we were seeing a new type of supernova."
Computer simulations to see what kind of process could have produced such a result suggest that a pair of white dwarves are involved; one of them stealing helium from the other. When the thief star's helium load rises past a certain point, the explosion occurs.

"The donor star is probably completely destroyed in the process, but we're not quite sure about the fate of the thief star," said team member Avishay Gal-Yam.

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