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The Question

(Submitted August 08, 1997)

Could the Gamma-ray burst we are seeing be the effects of the formation of a new black hole(s)? Can it be that we are seeing the creation of an event horizon - similar to the breaking of a rubber band? Since the bursts last from about 30ms to over 1000s, could they be related to the size of the star (3km = 30ms) and possibly to a cascaded black hole creation event (1000sec.+) involving several massive stars like in the center of a galaxy?

The Answer

In theory, the formation of an event horizon can occur without any excitement whatsoever. It is not like the breaking of a rubber band, but more like an animal descending below the surface of the water. This can occur quietly, like a whale swimming down to look for squid, or violently, like the winner of the 1997 Texas Belly Flop Competition.

Although the creation of an event horizon and the formation of a black hole need not necessarily create a burst of gamma-rays, most models of gamma-ray bursts end up with a black hole. This is because the energy required (assuming these sources are cosmological) is a large fraction of the mass of a star and the time scales are indeed comparable to the size of an event horizon for such a mass. Specifically, the currently most popular GRB model involves two neutron stars colliding with each other, a process which forms a black hole. (Nobody quite knows how such an event would produce gamma-rays, but the formation of a black hole at the end is thought to be inevitable.)

David Palmer and Jim Lochner
for Ask an Astrophysicist

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