User:Dmitry Brant/temp1

In general relativity, a black hole is a region of space in which the gravitational field is so powerful that nothing, including light, can escape its pull. Black holes are believed to form naturally as one possible end product of stellar evolution, when a sufficiently massive star collapses under its own gravity after exhausting its supply of nuclear fuel. In addition to stellar-mass black holes, there is evidence for the existence of intermediate-mass black holes, such as those in the centers of globular clusters, as well as supermassive black holes in the centers of galaxies, including our own Milky Way. Although there is no known natural process that creates black holes smaller than of stellar mass (except hypothetical primordial black holes formed during the Big Bang), in theory, any amount of matter can become a black hole if it is compressed into a volume of space with a radius smaller than the Schwarzchild radius for the given quantity of matter.

A defining feature of a black hole is its event horizon, which is a logical boundary around its center, the extents of which are proportional to the black hole's mass. Anything that crosses past the event horizon can never escape, and is doomed to continue falling towards the center, eventually colliding with, and becoming part of, a single point of zero volume and infinite density known as a singularity, which is where all of the black hole's mass is stored for the remainder of its lifetime. Since light is also trapped within the event horizon, the volume enclosed by the horizon appears "black" to an outside observer, giving the phenomenon its name. The horizon can be considered in classical terms as the boundary around the central singularity where an object's escape velocity is equal to the speed of light (within this boundary, escape velocity exceeds the speed of light). However, a more complete understanding of the event horizon is given by general relativity, which reveals that the existence of such a horizon is a consequence of the extreme curvature of spacetime caused by the presence of very dense matter, such as a collapsed star.

Despite its invisible interior, a black hole can reveal its presence through gravitational interaction with other matter in the surrounding environment. The presence of a black hole can be inferred by tracking the movement of a group of stars that orbit a region in space which appears empty. It can also be inferred by observing microquasars and active galactic nuclei, where material falling into a nearby black hole is significantly heated and emits a large amount of X-ray radiation that can be detected from earthbound and earth-orbiting telescopes. Such observations have resulted in the general scientific consensus that, barring a breakdown in our understanding of nature, black holes do exist in our universe.