The Greatest Show in Space

A brilliant cosmic blast stirs fears of another, far closer to Earth

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Chandra X-Ray Center / NASA / AP

This artist's illustration provided by NASA shows what the brightest supernova ever recorded, known as SN 2006gy, may have looked like when it exploded.

Remember the supernova, that great burst of sky violence that was supposed to be the finest pyrotechnics show the heavens could offer? Forget it. NASA's Chandra X-Ray Observatory and several ground-based optical telescopes have just witnessed a cosmic blast that makes the supernova look like a popgun.

The explosion, the subject of a paper that will appear in an upcoming issue of the Astrophysical Journal, took place 240 million light-years away and was, in the words of astronomer Nathan Smith of the University of California, Berkeley, a leader of the observing team, "truly monstrous." About 100 times as powerful as an ordinary supernova, it resulted from the death of a star that was probably 150 times as massive as our sun, or "as massive as a star can get," says Smith. What's more, a similarly huge and unstable star is rumbling a lot closer to Earth than we might like.

The super-duper nova, dubbed SN 2006gy, was set apart from the more common variety by what happened in the center of the star as it was dying. Typically, a massive star exhausts the elemental fuel in its core and begins to collapse inward. The outer layers blow off in a huge flare we recognize as a supernova while the core becomes more and more compressed, eventually forming the infinitely dense node that is a black hole. In SN 2006gy, the sheer mass of the star produced so much core heat and gamma-ray radiation that it created matter and antimatter particle pairs. This blew the star to bits, leaving no cold core behind.

The good news is that this kind of eruption may have been one of the events that allowed the universe as we know it to take shape in the first place, as similar supercharged supernovas seeded the heavens with new elements instead of hoarding their matter the way black holes do. The bad news is that the massive star Eta Carinae, one of the Milky Way's own, appears similarly unstable. Its brightness has been fluctuating for two centuries, and lately it looks much the way the erupting SN 2006gy did in the final stages before it blew.

At just 7,500 light-years away, Eta Carinae is square in our cosmic ZIP code. An explosion--which could occur soon or just as easily not--would release deadly gamma radiation, but the finely focused beam in which the rays travel means the danger is likely to pass us by. The fireworks, meanwhile, would be "the best star show in the history of modern civilization," says astronomer Mario Livio of the Space Telescope Science Institute in Baltimore. But after many months, the light would flicker out, and Eta Carinae would be no more. [This article consists of a complex diagram. Please see hardcopy of magazine.] When Stars Die • Our Sun • Supernovas • The Superstars