Two teams of researchers have proposed competing explanations for one of the most brilliant—and puzzling—supernovas in the observable universe, 2006gy.
Burning 240 million light-years away in the constellation Perseus, the stellar explosion has baffled scientists since it was spotted more than a year ago, because it is at least ten times too bright to have come from the routine collapse of a star's core.
One of the studies, led by Simon Portegies Zwart of the University of Amsterdam in the Netherlands, proposes that the supernova was created during a collision between two massive stars.
The other paper, led by Stan Woosley at the University of California, Santa Cruz, suggests that the supernova arose from collisions between shells of matter exploding sequentially out of a single, supermassive star.
Both papers appear in this week's issue of the journal Nature.
Stellar Smash-Up
To have caused a supernova of the observed size, 2006gy would have to have been a real giant—a hundred or more times the mass of the sun—according to Portegies Zwart and co-author Edward P.J. van den Huevel of the University of Amsterdam and the University of California, Santa Barbara.
But there's too much hydrogen in the supernova's chemical signature to endorse that scenario, the researchers point out. Stars more than 40 solar masses shed their hydrogen envelopes long before they explode.
2006gy, however, occurs near the center of its galaxy, where frequent stellar collisions could create an unusually massive star.
One scenario best explains 2006gy's unusual brightness and the presence of hydrogen in the supernova and the space around it, the researchers say.
A star a hundred times as massive as the sun—in the final phases of depleting the hydrogen in its core—collided with a hydrogen-rich sunlike star of 10 to 40 solar masses.
The smaller, younger star would have infused the old star with hydrogen tens or hundreds of thousands of years before the onset of its fiery death throes, explaining the hydrogen that remained afterwards.
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