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Black hole
From Wikipedia, the free encyclopedia
For other uses, see Black hole (disambiguation).

Simulated view of a black hole (center) in front of theLarge Magellanic Cloud. Note the gravitational lensingeffect, which produces two enlarged but highly distorted views of the Cloud. Across the top, the Milky Way disk appears distorted intoan arc.
General relativity |
Introduction
Mathematical formulation
Resources |
Fundamental concepts[show] |
Phenomena[hide]Kepler problem · Lenses · Waves
Frame-dragging · Geodetic effect
Event horizon · Singularity
Black hole |
Equations[show] |
Advanced theories[show] |
Solutions[show] |
Scientists[show] |
* v  * t  * e |
A black hole is a region of spacetime wheregravity prevents anything, including light, from escaping.[1] The theory of general relativitypredicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that marks the point of no return. It is called "black" because it absorbs all the light that hits the horizon, reflecting nothing,just like a perfect black bodyin thermodynamics.[2][3] Quantum mechanicspredicts that black holes emit radiation like a black body with a finite temperature. 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 firstconsidered 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. Long considered a mathematical curiosity, it was during the 1960s thattheoretical work showed black holes were a generic prediction of general relativity. The discovery of neutron stars sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality.
Black holes of stellar mass are expected to form when very massive stars collapse at the end of their life cycle. After a black hole has formed it can continue to grow by absorbing massfrom its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses may form. There is general consensus that supermassive black holes exist in the centers of most galaxies.
Despite its invisible interior, the presence of a black hole can be inferred through its interaction with othermatter and with light and other electromagneticradiation. Matter falling onto a black hole can form anaccretion disk heated by friction, forming some of the brightest objects in the universe. If there are other stars orbiting a black hole, their orbit can be used to determine its mass and location. This data can be used to exclude possible alternatives (such as neutron stars). In this way, astronomers have identified numerous stellar blackhole 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.
Contents  [hide]  * 1 History * 1.1 General relativity * 1.2 Golden age * 2 Properties and structure * 2.1 Physical properties * 2.2 Event horizon * 2.3 Singularity * 2.4 Photon sphere * 2.5 Ergosphere* 3 Formation and evolution * 3.1 Gravitational collapse * 3.2 High-energy collisions * 3.3 Growth * 3.4 Evaporation * 4 Observational evidence * 4.1 Accretion of matter * 4.2 X-ray binaries * 4.3 Galactic nuclei * 4.4 Gravitational lensing * 4.5 Alternatives * 5 Open questions * 5.1 Entropy and thermodynamics * 5.2 Black hole unitarity...