A supernova that's the first of its kind

An extraordinarily bright, long-lasting supernova named SN 2007bi, snagged in a search by a robotic telescope, turns out to be the first example of the kind of stars that first populated the universe. The bright supernova occurred in a nearby dwarf galaxy, a kind of galaxy that's common but has been studied little until now. The unusual supernova could be the first of many such events soon to be discovered.

The supernova's spectrum was unusual, and the analysis indicated that the supernova's precursor star only could have been a giant weighing at least 200 times the mass of our Sun and initially containing few elements besides hydrogen and helium — a star like the very first stars in the early universe.

"Because the core alone was some 100 solar masses, the long-hypothesized phenomenon called pair instability must have occurred," said astrophysicist Peter Nugent, a member of the SNfactory. "In the extreme heat of the star's interior, energetic gamma rays created pairs of electrons and positrons, which bled off the pressure that sustained the core against collapse."

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