Stellar Black Holes
Artist's depiction of a stellar-mass black hole with its accretion disc.(3—100 M⊙) A stellar black hole (or stellar-mass black hole—see graphic) is one formed by the gravitational collapse of a massive star, a cataclysmic event commonly observed as a supernova explosion or gamma ray burst. Such objects have masses ranging from about 3 to several tens of solar masses. By the no-hair theorem, it is possible to completely characterize any black hole using only three externally observable classical parameters: mass, angular momentum (spin), and electric charge. Naturally occurring stellar black holes always have mass, and also spin, inherited from the conservation of the mass and angular momentum of the stars giving birth to them. On the other hand, electrically charged black holes—especially small ones—are a staple of science fiction, since their charges can be exploited by hypothetical electromagnetic confinement schemes that keep them from falling out of control (see for example "The Borderland of Sol" by Larry Niven, below).
The gravitational collapse of a star is a natural process that may produce a black hole, although it doesn't have to. Some sort of cataclysm is inevitable at the end of a star's life, as the stellar energy sources that have generated the heat and radiation pressure counterbalancing the attraction of gravity become exhausted. If the mass of the collapsing part of the star is below a certain critical value, the end product will be a compact star, either a white dwarf or a neutron star, although neither type can exceed the critical mass limit. For large stars whose mass does exceed this maximum, the infall will continue forever in a catastrophic gravitational collapse that forms a black hole. The limit of the mass of a neutron star is not well known: In 1939, it was estimated at 0.7 solar masses, called the Tolman–Oppenheimer–Volkoff (TOV) limit. In 1996, a different estimate put this maximum value (and hence the minimum mass of a stellar black hole) in a range from 1.5 to 3 M⊙.
Read more about this topic: Black Holes In Fiction, Classification of Black Holes
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