John Archibald Wheeler coined the term to describe a collapsed star whose gravitational field is so intense that not even light can escape.
The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole.
- This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of stellar mass or greater.
- Objects whose gravity field is too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace.
- The first modern solution of general relativity that would characterize a black hole was found by Karl Schwarzschild in 1916, although its interpretation as a region of space from which nothing can escape was not fully appreciated for another four decades.
- The discovery of neutron stars sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality.
- In this way, astronomers have identified numerous stellar black hole candidates in binary systems, and established that the core of our Milky Way galaxy contains a supermassive black hole of about 4.3 million solar masses.
- In 1958, David Finkelstein identified the Schwarzschild surface as an event horizon, “a perfect unidirectional membrane: causal influences can cross it in only one direction”. Until that time, neutron stars, like black holes, were regarded as just theoretical curiosities; but the discovery of pulsars showed their physical relevance and spurred a further interest in all types of compact objects that might be formed by gravitational collapse.
- The analogy was completed when Hawking, in 1974, showed that quantum field theory predicts that black holes should radiate like a black body with a temperature proportional to the surface gravity of the black hole.
- The no-hair theorem states that, once it achieves a stable condition after formation, a black hole has only three independent physical properties: mass, charge, and angular momentum.
- Charged black holes are described by the Reissner–Nordström metric, while the Kerr metric describes a rotating black hole.
- In 1974, Hawking showed that black holes are not entirely black but emit small amounts of thermal radiation; an effect that 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 in a perfect black body spectrum.