"Brightest Supernova" Reveals New Kind of Star Death

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For their study, Smith, Pooley, and colleagues examined images of SN 2006gy taken from space by NASA's Chandra X-Ray Observatory and from the ground by the Lick Observatory in California and the Keck Observatory in Hawaii.

(See more images from the Chandra X-Ray Observatory.)

The results will appear in an upcoming issue of the Astrophysical Journal.

The team surmised that the explosion was the first recorded example of a type of supernova called a pair-instability mechanism, which was first proposed in scientific literature in the 1960s.

The phenomenon has likely never been seen until now because today such extreme stellar bodies are few and far between.

"Like people over seven feet [two meters] tall, stars that are over a hundred times the mass of our sun are very rare," Smith said.

In such heavy stars, radiation created by fusion in the core balances the pressure of the star's gravity.

When fusion stops, the star begins to collapse, crunching its core into a black hole or neutron star.

In the subsequent explosion, the star emits material equal to only about 5 percent of the sun's mass.

The pair-instability theory states that the gamma radiation that normally holds very massive stars together can start to produce pairs of particles and anti-particles when the core gets hot enough.

(Related news: "Massive Cosmic Explosion Has Astronomers Stumped" [December 20, 2006].)

"The minute the radiation starts putting energy into creating particles, the star loses support," Mario Livio, of the Space Telescope Science Institute, said at the briefing.

Such a scenario would allow the star to "jump the gun" and explode before its core collapses.

"Instead of the core of [SN 2006gy's star] collapsing, the core was completely obliterated and the explosion spewed matter out into space," UC Berkeley's Smith said. This material was equal to roughly 20 times the mass of the sun.

Scientists believe that the early universe was populated with similar supermassive stars that died by the pair-instability mechanism.

Instead of creating black holes that sucked up their material, these dying stars "polluted" the space around them, seeding the universe with the elements needed for life.

Neighborhood Radiation

Closer to home, the massive star Eta Carinae was observed in the 1840s ejecting lobes of material that resemble the bulbs of gases seen around SN 2006gy.

Does this mean the star's death could eject radiation that would be harmful to life on Earth?

"That's not very likely," Livio said.

If jets of gamma rays were aimed directly at the planet, that could affect us, he said. But the chances of that happening are very slim.

What's more, there's no guarantee that the star will explode in the same way. And even if it did, it could happen tomorrow or a hundred thousand years from now.

"We can sleep quietly tonight," Livio said.

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