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The Question
(Submitted May 19, 1997)
Could gamma-ray bursts be due to evaporating mini-black holes
as suggested by Stephen Hawking (1974)?
The Answer
This is a very good question, one that gamma-ray astronomers have thought
seriously about. They have concluded that evaporating mini-black holes
are unlikely to be the origin of (at least the majority of) gamma-ray
bursts (GRBs).
Here are some of the reasons:
Every GRB is different: some are complex, some are simple, some are long,
some are short, some are hard, some are soft. But every decaying black hole
is the same (except for angular momentum and surrounding material).
Decaying black holes have well predicted time and energy behavior. What
is expected from a black hole decay is a brief, rapidly hardening flash
which would be most observable by Comptel or EGRET. Comptel and EGRET have
looked for such, and not found any.
Decaying black holes don't decay unless they are relatively small, so they
don't have very much energy, thus they must be in our immediate neighborhood
to be seen. In contrast, the distribution of observed GRBs on the sky
implies that they are either at cosmological distances or at least rather
far out in the Galactic halo.
David Palmer and Koji Mukai
for Ask a High-Energy Astronomer
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