Head-On Collision

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Just because a star is "dead" doesn't mean it can't put on a lively show. The dead remnants of stars like the Sun, for example, can blast themselves to bits. But they need some help -- usually a nearby "normal" star, or in one case, perhaps another dead star.

These stellar remnants are known as white dwarfs. A white dwarf forms when a normal star reaches the end of its life and casts its outer layers into space. All that remains is the hot, dense core, which no longer produces energy -- a white dwarf.

But if it has a nearby companion star, the white dwarf may steal some of its gas. If enough gas builds up, it can trigger an explosion that blasts the white dwarf to bits as a supernova. The blast can outshine an entire galaxy of normal stars.

A supernova that was discovered in late 2006 was brighter than most. Last year, astronomers at the Harvard-Smithsonian Center for Astrophysics came up with a possible reason. They said the explosion was caused by a collision between two white dwarfs.

Not only was the explosion unusually bright, but its residue contained unusually large amounts of carbon and silicon. The astronomers said the brightness and composition fit the model for a white dwarf collision. When the two stars came together, they were pushed above the "weight limit" for white dwarfs, setting off a powerful blast -- a final, lively act for two dead stars.

We'll talk about another odd supernova tomorrow.

Script by Damond Benningfield, Copyright 2008

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