"Brightest Supernova" Reveals New Kind of Star Death

Victoria Jaggard in Washington, D.C.
National Geographic News
May 8, 2007

The brightest star explosion ever seen has been spotted about 240 million light-years away in the constellation Perseus, researchers announced yesterday.

The distant event, which so far has remained brighter than an ordinary supernova for more than 200 days, likely represents a new and extremely rare type of star death that occurs only in supermassive stars.

"It's no surprise that a very massive star will eventually collapse," David Pooley, an astrophysicist at the University of California, Berkeley, and co-author of a new study on the supernova, said during a press briefing.

What surprised scientists is that the brightness of the explosion couldn't be explained by the faint amount of x-rays emitted by the blast.

Normally when a large star dies, the explosion sends shockwaves through surrounding cooler gases, creating regions that emit large amounts of x-rays—the source of a supernova's light.

But the explosion of SN 2006gy, which is thought to be nearly 150 times as massive as the sun, showed few x-rays.

This suggests that the light is being produced from hot material being ejected into space.

"This would require a new type of [explosion] mechanism that has been produced theoretically but never observed," study leader Nathan Smith said at the briefing.

Cosmic Instability

The finding has ramifications for Eta Carinae, the most massive star in our galaxy, which lies just 7,400 light years away.

This star, estimated to be 100 to 120 times the sun's mass, has been experiencing preliminary eruptions that could mean it will explode in a manner similar to SN 2006gy.

If such a supernova occurred in our galaxy, "it would be so bright that you could see it [from Earth] during the day and you could even read a book by its light at night," Pooley said.

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