“black hole”的概念、定义、翻译、参考文献-科学参考

black hole

Physics

An object in space that has collapsed under its own gravitational forces to such an extent that its escape velocity is equal to the speed of light. Black holes are believed to be formed in the gravitational collapse of very large stars at the ends of their lives (see death of a star; stellar evolution; supernova). If the mass of an evolved stellar core is greater than the analogue of the Chandrasekhar limit for neutron stars then neutron degeneracy pressure is unable to prevent contraction until the gravitational field is sufficiently strong to prevent the escape of electromagnetic radiation. The boundary of the black hole, known as the event horizon, is the surface in space at which the gravitational field reaches this critical value. Events occurring within this horizon (i.e. in the interior of the black hole) cannot be observed from outside.

The theoretical study of black holes involves the use of general relativity. It has been shown that a black hole can be characterized uniquely by just three properties: its mass, angular momentum, and electrical charge (this is known as the no-hair theorem). Mathematical expressions have been derived for describing black holes; these are the Schwarzschild solution (uncharged nonrotating hole), the Reissner–Nordstrøm solution (charged nonrotating hole), the Kerr solution (uncharged rotating hole), and the Kerr–Newman solution (charged rotating hole).

The ultimate fate of matter inside the black hole’s event horizon is as yet unknown. General relativity predicts that at the centre of the hole there is a singularity, a point at which the density becomes infinite and the presently understood laws of physics break down. It is possible that a successful quantum theory of gravity could resolve this problem. However, since any singularity is hidden within the event horizon, it cannot influence the outside universe, so the normal laws of physics, including general relativity, can be used to describe processes outside the black hole.

Observational evidence of objects thought to be black holes comes from their effect on surrounding matter. Thus, if a black hole is part of a binary system with another star it will attract and capture matter from this star. The material leaving the star first forms a rotating accretion disk around the black hole, in which the matter becomes compressed and heated to such an extent that it emits X-rays. In the constellation Cygnus there is an X-ray source, Cygnus X-1, which consists of a supergiant star revolving around a small invisible companion with a mass of about ten times that of the sun, and therefore well above the Chandrasekhar limit. The companion is thought to be a black hole. Black holes have also been postulated as the power sources of quasars and as possible generators of gravitational waves. It appears that there are very large (supermassive) black holes at the centre of all galaxies.

It has been suggested that the formation of a black hole is responsible for gamma-ray bursts, either by one dead star collapsing or by two neutron stars spiralling into each other. Theoreticians have also postulated the existence of ‘mini’ black holes (with masses of about 10¹² kilogram and radii about 10⁻¹⁵ metre). Such entities might have been formed shortly after the big bang when the universe was created. Quantum-mechanical effects are important for mini black holes, which emit Hawking radiation (see Hawking process). Debates about how quantum mechanics affects black holes are still continuing. See also Schwarzschild radius.

http://hubblesite.org/explore_astronomy/black_holes/home.html A NASA website with information about black holes

Astronomy

An object with such a strong gravitational field that its escape velocity exceeds the velocity of light. One way in which black holes are believed to form is when massive stars collapse at the end of their lives. A collapsing object becomes a black hole when its radius has shrunk to a critical size, known as the Schwarzschild radius, and light can no longer escape from it. The surface having this critical radius is referred to as the event horizon, and marks the boundary inside which all information is trapped. Hence events within the black hole cannot be observed from outside. Theory indicates that both space and time become distorted inside the event horizon and that an object collapses to a single point, a singularity, at the centre of a black hole. Black holes may have any mass. Supermassive black holes (10⁵ solar masses) may exist at the centres of active galaxies. At the other extreme, mini black holes of radii 10⁻¹⁰ m and masses similar to that of an asteroid may have been formed in the extreme conditions following the Big Bang.
An accretion disk may form around a black hole when matter falls towards it from a nearby companion star or other source. Energy predominantly at X-ray wavelengths is produced as matter in the accretion disk loses momentum and spirals in; these X-rays can be detected by satellites in orbit. Several black-hole candidates have been located in our Galaxy, most famously Cygnus X-1. In addition, there is good evidence for a supermassive black hole of 3–4 million solar masses at the centre of our Galaxy. The accretion disk around the supermassive black hole at the centre of the galaxy M87 was imaged by the *Event Horizon Telescope in 2019; the black hole's mass was estimated at 6.5 billion solar masses and the diameter of its event horizon as nearly 40 billion km.
There are several theoretically possible forms of black hole. A non-rotating black hole without electrical charge is known (after K. Schwarzschild) as a Schwarzschild black hole. A non-rotating black hole with electrical charge is termed a Reissner–Nordström black hole after the German physicist Hans Jacob Reissner (1874–1967) and the Finn Gunnar Nordström (1881–1923). In practice, black holes are likely to be rotating and uncharged, a form known as a Kerr black hole. Black holes are not entirely black; theory suggests that they can emit energy in the form of Hawking radiation.

Space Exploration

An object in space whose gravity is so great that nothing can escape from it, not even light. It is thought to form when a massive star shrinks at the end of its life. A black hole sucks in more matter, including other stars, from the space around it. Matter that falls into a black hole is squeezed to infinite density at the centre of the hole. Black holes can be detected because gas falling towards them becomes so hot that it emits X-rays.
Black holes containing the mass of millions of stars are thought to lie at the centres of quasars. Satellites have detected X-rays from a number of objects that may be black holes, but only a small number of likely black holes have been identified in our Galaxy.
Cygnus X-1, first discovered in 1964 by astronomers at the US Naval Research Laboratory, is an X-ray source in the constellation of Cygnus. A0620–00, in the constellation of Monoceros, is one of the best black-hole candidates in the Galaxy, discovered in the 1980s by US astronomers Jeffrey McClintock of the Harvard-Smithsonian Center for Astrophysics and Ronald Remillard of the Massachusetts Institute of Technology. V404 Cygni, close to Cygnus X-1, is a possible black hole discovered in 1992. Nova Muscae, identified as a black hole in 1992 by McClintock, Remillard, and US astronomer Charles Bailyn of Yale University, New Haven, Connecticut, lies approximately 18 000 light years from Earth. The Hubble Space Telescope discovered in 1997 evidence of a black hole 300 million times the mass of the Sun. It is located in the middle of galaxy M84 about 50 million light years from Earth. In March 2001, NASA scientists, using images from the orbiting Chandra X-Ray Observatory of X-ray emissions from space objects as they may have appeared 12 billion years ago, concluded that there may have been about 300 billion black holes when the universe was young.
In April 2019 an international team of 200 astronomers from 20 countries unveiled for the first time an image of a black hole’s event horizon. The image was reconstructed from four days of synchronized observations with eight *radio telescopes located in Arizona, Hawaii, Mexico, Chile, Spain, and Antarctica, pointed in tandem at Messier 87 — a giant elliptical galaxy some 50 million light years distant. Collectively known as the Event Horizon Telescope, the global array effectively produced the light-gathering power of a radio telescope with a dish diameter approaching that of the Earth, giving it the ability to resolve objects such as the event horizon a supermassive black hole. This long-sought image provides the strongest evidence to date for the existence of supermassive black holes and opens a new window onto the study of black holes, their event horizons, and gravity.
http://archive.ncsa.illinois.edu/Cyberia/NumRel/BlackHoles.html Well-written guide to black holes. There is a good balance of text and images, with clear explanatory diagrams. Video and audio clips of scientists explain some of the current theories of the evolution and behaviour of black holes.

Internet

A mythical location in a network where lost data or emails end up.

单词	black hole
释义	black hole Physics An object in space that has collapsed under its own gravitational forces to such an extent that its escape velocity is equal to the speed of light. Black holes are believed to be formed in the gravitational collapse of very large stars at the ends of their lives (see death of a star; stellar evolution; supernova). If the mass of an evolved stellar core is greater than the analogue of the Chandrasekhar limit for neutron stars then neutron degeneracy pressure is unable to prevent contraction until the gravitational field is sufficiently strong to prevent the escape of electromagnetic radiation. The boundary of the black hole, known as the event horizon, is the surface in space at which the gravitational field reaches this critical value. Events occurring within this horizon (i.e. in the interior of the black hole) cannot be observed from outside. The theoretical study of black holes involves the use of general relativity. It has been shown that a black hole can be characterized uniquely by just three properties: its mass, angular momentum, and electrical charge (this is known as the no-hair theorem). Mathematical expressions have been derived for describing black holes; these are the Schwarzschild solution (uncharged nonrotating hole), the Reissner–Nordstrøm solution (charged nonrotating hole), the Kerr solution (uncharged rotating hole), and the Kerr–Newman solution (charged rotating hole). The ultimate fate of matter inside the black hole’s event horizon is as yet unknown. General relativity predicts that at the centre of the hole there is a singularity, a point at which the density becomes infinite and the presently understood laws of physics break down. It is possible that a successful quantum theory of gravity could resolve this problem. However, since any singularity is hidden within the event horizon, it cannot influence the outside universe, so the normal laws of physics, including general relativity, can be used to describe processes outside the black hole. Observational evidence of objects thought to be black holes comes from their effect on surrounding matter. Thus, if a black hole is part of a binary system with another star it will attract and capture matter from this star. The material leaving the star first forms a rotating accretion disk around the black hole, in which the matter becomes compressed and heated to such an extent that it emits X-rays. In the constellation Cygnus there is an X-ray source, Cygnus X-1, which consists of a supergiant star revolving around a small invisible companion with a mass of about ten times that of the sun, and therefore well above the Chandrasekhar limit. The companion is thought to be a black hole. Black holes have also been postulated as the power sources of quasars and as possible generators of gravitational waves. It appears that there are very large (supermassive) black holes at the centre of all galaxies. It has been suggested that the formation of a black hole is responsible for gamma-ray bursts, either by one dead star collapsing or by two neutron stars spiralling into each other. Theoreticians have also postulated the existence of ‘mini’ black holes (with masses of about 10¹² kilogram and radii about 10⁻¹⁵ metre). Such entities might have been formed shortly after the big bang when the universe was created. Quantum-mechanical effects are important for mini black holes, which emit Hawking radiation (see Hawking process). Debates about how quantum mechanics affects black holes are still continuing. See also Schwarzschild radius. http://hubblesite.org/explore_astronomy/black_holes/home.html A NASA website with information about black holes Astronomy An object with such a strong gravitational field that its escape velocity exceeds the velocity of light. One way in which black holes are believed to form is when massive stars collapse at the end of their lives. A collapsing object becomes a black hole when its radius has shrunk to a critical size, known as the Schwarzschild radius, and light can no longer escape from it. The surface having this critical radius is referred to as the event horizon, and marks the boundary inside which all information is trapped. Hence events within the black hole cannot be observed from outside. Theory indicates that both space and time become distorted inside the event horizon and that an object collapses to a single point, a singularity, at the centre of a black hole. Black holes may have any mass. Supermassive black holes (10⁵ solar masses) may exist at the centres of active galaxies. At the other extreme, mini black holes of radii 10⁻¹⁰ m and masses similar to that of an asteroid may have been formed in the extreme conditions following the Big Bang. An accretion disk may form around a black hole when matter falls towards it from a nearby companion star or other source. Energy predominantly at X-ray wavelengths is produced as matter in the accretion disk loses momentum and spirals in; these X-rays can be detected by satellites in orbit. Several black-hole candidates have been located in our Galaxy, most famously Cygnus X-1. In addition, there is good evidence for a supermassive black hole of 3–4 million solar masses at the centre of our Galaxy. The accretion disk around the supermassive black hole at the centre of the galaxy M87 was imaged by the Event Horizon Telescope in 2019; the black hole's mass was estimated at 6.5 billion solar masses and the diameter of its event horizon as nearly 40 billion km. There are several theoretically possible forms of black hole. A non-rotating black hole without electrical charge is known (after K. Schwarzschild) as a Schwarzschild black hole. A non-rotating black hole with electrical charge is termed a Reissner–Nordström black hole* after the German physicist Hans Jacob Reissner (1874–1967) and the Finn Gunnar Nordström (1881–1923). In practice, black holes are likely to be rotating and uncharged, a form known as a Kerr black hole. Black holes are not entirely black; theory suggests that they can emit energy in the form of Hawking radiation. Space Exploration An object in space whose gravity is so great that nothing can escape from it, not even light. It is thought to form when a massive star shrinks at the end of its life. A black hole sucks in more matter, including other stars, from the space around it. Matter that falls into a black hole is squeezed to infinite density at the centre of the hole. Black holes can be detected because gas falling towards them becomes so hot that it emits X-rays. Black holes containing the mass of millions of stars are thought to lie at the centres of quasars. Satellites have detected X-rays from a number of objects that may be black holes, but only a small number of likely black holes have been identified in our Galaxy. Cygnus X-1, first discovered in 1964 by astronomers at the US Naval Research Laboratory, is an X-ray source in the constellation of Cygnus. A0620–00, in the constellation of Monoceros, is one of the best black-hole candidates in the Galaxy, discovered in the 1980s by US astronomers Jeffrey McClintock of the Harvard-Smithsonian Center for Astrophysics and Ronald Remillard of the Massachusetts Institute of Technology. V404 Cygni, close to Cygnus X-1, is a possible black hole discovered in 1992. Nova Muscae, identified as a black hole in 1992 by McClintock, Remillard, and US astronomer Charles Bailyn of Yale University, New Haven, Connecticut, lies approximately 18 000 light years from Earth. The Hubble Space Telescope discovered in 1997 evidence of a black hole 300 million times the mass of the Sun. It is located in the middle of galaxy M84 about 50 million light years from Earth. In March 2001, NASA scientists, using images from the orbiting Chandra X-Ray Observatory of X-ray emissions from space objects as they may have appeared 12 billion years ago, concluded that there may have been about 300 billion black holes when the universe was young. In April 2019 an international team of 200 astronomers from 20 countries unveiled for the first time an image of a black hole’s event horizon. The image was reconstructed from four days of synchronized observations with eight *radio telescopes located in Arizona, Hawaii, Mexico, Chile, Spain, and Antarctica, pointed in tandem at Messier 87 — a giant elliptical galaxy some 50 million light years distant. Collectively known as the Event Horizon Telescope, the global array effectively produced the light-gathering power of a radio telescope with a dish diameter approaching that of the Earth, giving it the ability to resolve objects such as the event horizon a supermassive black hole. This long-sought image provides the strongest evidence to date for the existence of supermassive black holes and opens a new window onto the study of black holes, their event horizons, and gravity. http://archive.ncsa.illinois.edu/Cyberia/NumRel/BlackHoles.html Well-written guide to black holes. There is a good balance of text and images, with clear explanatory diagrams. Video and audio clips of scientists explain some of the current theories of the evolution and behaviour of black holes. Internet A mythical location in a network where lost data or emails end up.
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