<P> Gravitational collapse is not the only process that could create black holes . In principle, black holes could be formed in high - energy collisions that achieve sufficient density . As of 2002, no such events have been detected, either directly or indirectly as a deficiency of the mass balance in particle accelerator experiments . This suggests that there must be a lower limit for the mass of black holes . Theoretically, this boundary is expected to lie around the Planck mass (m = √ ħ c / G ≈ 7019120000000000000 ♠ 1.2 × 10 GeV / c ≈ 6992220000000000000 ♠ 2.2 × 10 kg), where quantum effects are expected to invalidate the predictions of general relativity . This would put the creation of black holes firmly out of reach of any high - energy process occurring on or near the Earth . However, certain developments in quantum gravity suggest that the Planck mass could be much lower: some braneworld scenarios for example put the boundary as low as 7000100000000000000 ♠ 1 TeV / c . This would make it conceivable for micro black holes to be created in the high - energy collisions that occur when cosmic rays hit the Earth's atmosphere, or possibly in the Large Hadron Collider at CERN . These theories are very speculative, and the creation of black holes in these processes is deemed unlikely by many specialists . Even if micro black holes could be formed, it is expected that they would evaporate in about 10 seconds, posing no threat to the Earth . </P> <P> Once a black hole has formed, it can continue to grow by absorbing additional matter . Any black hole will continually absorb gas and interstellar dust from its surroundings . This is the primary process through which supermassive black holes seem to have grown . A similar process has been suggested for the formation of intermediate - mass black holes found in globular clusters . Black holes can also merge with other objects such as stars or even other black holes . This is thought to have been important, especially in the early growth of supermassive black holes, which could have formed from the aggregation of many smaller objects . The process has also been proposed as the origin of some intermediate - mass black holes . </P> <P> In 1974, Hawking predicted that black holes are not entirely black but emit small amounts of thermal radiation; this effect has become known as Hawking radiation . By applying quantum field theory to a static black hole background, he determined that a black hole should emit particles that display a perfect black body spectrum . Since Hawking's publication, many others have verified the result through various approaches . If Hawking's theory of black hole radiation is correct, then black holes are expected to shrink and evaporate over time as they lose mass by the emission of photons and other particles . The temperature of this thermal spectrum (Hawking temperature) is proportional to the surface gravity of the black hole, which, for a Schwarzschild black hole, is inversely proportional to the mass . Hence, large black holes emit less radiation than small black holes . </P> <P> A stellar black hole of 1 M has a Hawking temperature of 62 nanokelvins . This is far less than the 2.7 K temperature of the cosmic microwave background radiation . Stellar - mass or larger black holes receive more mass from the cosmic microwave background than they emit through Hawking radiation and thus will grow instead of shrink . To have a Hawking temperature larger than 2.7 K (and be able to evaporate), a black hole would need a mass less than the Moon . Such a black hole would have a diameter of less than a tenth of a millimeter . </P>

Who predicated that black holes emit radiation and what it is called
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