Primordial black hole
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A primordial black hole is a hypothetical type of black hole that is formed not by the gravitational collapse of a star but by the extreme densities of matter present during early universe.
In the first few moments after the big bang, pressure and temperature were extremely great. Under these conditions, simple fluctuations in the density of matter may have resulted in local regions dense enough to create black holes. Although most regions of high density would be quickly dispersed by the expansion of the universe, a primordial black hole would be stable, persisting to the present.
One way to detect primordial black holes is by their Hawking radiation. All black holes are believed to emit Hawking radiation at a rate inversely proportional to their mass. Since this emission further decreases their mass, black holes with very small mass would experience runaway evaporation, creating a massive burst of radiation. A regular black hole (of about 3 solar masses) cannot lose all of its mass within the lifetime of the universe (they would take about 1060 years to do so). However, since primordial black holes are not formed by stellar core collapse, they may be of any size. It has been calculated that primordial black holes that were created with a mass of about 1012 kg would have a lifetime about equal to the age of the universe. If these low-mass black holes exist, we should be able to observe some of these explosions today.
Although it is now considered unlikely, the evaporation of primordial black holes has been suggested as one possible explanation for gamma ray bursts. Some astronomers have also conjectured that primordial black holes could help account for the missing mass of the universe.
Even if they do not solve these problems, the low number of primordial black holes (they have never been detected) aids cosmologists by putting constraints on the spectrum of density fluctuations in the early universe.
See also
- black hole, a general survey
Classifification by type:
- Schwarzschild or static black hole
- rotating or Kerr black hole
- charged black hole or Newman black hole and Kerr-Newman black hole
A classification by mass:
- micro black hole and extra-dimensional black hole
- primordial black hole, a hypothetical leftover of the Big Bang
- stellar black hole, which could either be a static black hole or a rotating black hole
- intermediate-mass black hole
- supermassive black hole, which could also either be a static black hole or a rotating black hole