Stellar black hole
Encyclopedia
A stellar black hole is a black hole
formed by the gravitational collapse
of a massive star
. They have masses ranging from about 3 to several tens of solar mass
es. The process is observed as a supernova
explosion or as a gamma ray burst
.
The collapse of a star
is a natural process that can produce a black hole. It is inevitable at the end of the life of a star, when all stellar energy sources are exhausted. If the mass of the collapsing part of the star is below a certain critical value, the end product is a compact star
, either a white dwarf
or a neutron star
. Both these stars have a maximum mass. So if the collapsing star has a mass exceeding this limit, the collapse will continue forever (catastrophic gravitational collapse
) and form a black hole.
The maximum mass of a neutron star is not well known, in 1939 it was estimated at 0.7 solar masses, called the TOV limit. In 1996 a different estimate put this upper mass in a ranged from 1.5 to 3 solar masses.
In the theory of general relativity
, a black hole could exist of any mass. The lower the mass, the higher the density of matter has to be in order to form a black hole. (See, for example, the discussion in Schwarzschild radius
, the radius of a black hole.) There are no known processes that can produce black holes with mass less than a few times the mass of the Sun. If they exist, they are most likely primordial black hole
s. The largest known stellar black hole (as of 2007) is 15.65±1.45 solar masses. Additionally, there is evidence that the IC 10 X-1 X-ray source is a stellar black hole with a probable mass of 24-33 solar masses. As of April 2008, XTE J1650-500
was reported by NASA
and others to be the smallest mass black hole currently known to science, with a mass 3.8 solar masses and a diameter of only 15 miles (24 kilometers).
There is observational evidence for two other types of black holes, which are much more massive than stellar black holes. They are intermediate-mass black hole
s (in the centre of globular cluster
s) and supermassive black hole
s in the centre of the Milky Way
and active galaxies.
). The black hole therefore is observable in X-rays, whereas the companion star can be observed with optical telescopes. The energy release for black holes and neutron stars are of the same order of magnitude. Black holes and neutron stars are often difficult to distinguish.
However, neutron stars may have additional properties. They show differential rotation, and can have a magnetic field and exhibit localized explosions (thermonuclear bursts). Whenever such properties are observed, the compact object in the binary system is revealed as a neutron star.
The derived masses come from observations of compact X-ray sources (combining X-ray and optical data). All identified neutron stars have a mass below 3 to 5 solar masses. None of the compact systems with a mass above 5 solar masses reveals the properties of a neutron star. The combination of these facts make it more and more likely that the class of compact stars with a mass above 5 solar masses are in fact black holes.
Note that this proof of existence of stellar black holes is not entirely observational but relies on theory: We can think of no other object for these massive compact systems in stellar binaries than a black hole. A direct proof of the existence of a black hole would be if one actually observes the orbit of a particle (or a blob of gas) that falls into the black hole.
systems in which the compact object draws matter from its partner via an accretion disk. The probable black holes in these pairs range from three to more than a dozen solar mass
es.
Stellar-mass black hole candidates:
Black hole
A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts 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...
formed by the gravitational collapse
Gravitational collapse
Gravitational collapse is the inward fall of a body due to the influence of its own gravity. In any stable body, this gravitational force is counterbalanced by the internal pressure of the body, in the opposite direction to the force of gravity...
of a massive star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
. They have masses ranging from about 3 to several tens of solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
es. The process is observed as a supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
explosion or as a gamma ray burst
Gamma ray burst
Gamma-ray bursts are flashes of gamma rays associated with extremely energetic explosions that have been observed in distant galaxies. They are the most luminous electromagnetic events known to occur in the universe. Bursts can last from ten milliseconds to several minutes, although a typical...
.
Properties
By the no-hair theorem, a black hole can only have three fundamental properties: mass, electric charge and angular momentum (spin). It is believed that black holes formed in nature all have spin, but no definite observation on the spin have been performed. The spin of a stellar black hole is due to the conservation of angular momentum of the star that produced it.The collapse of a star
Gravitational collapse
Gravitational collapse is the inward fall of a body due to the influence of its own gravity. In any stable body, this gravitational force is counterbalanced by the internal pressure of the body, in the opposite direction to the force of gravity...
is a natural process that can produce a black hole. It is inevitable at the end of the life of a star, when all stellar energy sources are exhausted. If the mass of the collapsing part of the star is below a certain critical value, the end product is a compact star
Compact star
In astronomy, the term compact star is used to refer collectively to white dwarfs, neutron stars, other exotic dense stars, and black holes. These objects are all small for their mass...
, either a white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
or a neutron star
Neutron star
A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
. Both these stars have a maximum mass. So if the collapsing star has a mass exceeding this limit, the collapse will continue forever (catastrophic gravitational collapse
Gravitational collapse
Gravitational collapse is the inward fall of a body due to the influence of its own gravity. In any stable body, this gravitational force is counterbalanced by the internal pressure of the body, in the opposite direction to the force of gravity...
) and form a black hole.
The maximum mass of a neutron star is not well known, in 1939 it was estimated at 0.7 solar masses, called the TOV limit. In 1996 a different estimate put this upper mass in a ranged from 1.5 to 3 solar masses.
In the theory of general relativity
General relativity
General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics...
, a black hole could exist of any mass. The lower the mass, the higher the density of matter has to be in order to form a black hole. (See, for example, the discussion in Schwarzschild radius
Schwarzschild radius
The Schwarzschild radius is the distance from the center of an object such that, if all the mass of the object were compressed within that sphere, the escape speed from the surface would equal the speed of light...
, the radius of a black hole.) There are no known processes that can produce black holes with mass less than a few times the mass of the Sun. If they exist, they are most likely primordial black hole
Primordial black hole
A primordial black hole is a hypothetical type of black hole that is formed not by the gravitational collapse of a large star but by the extreme density of matter present during the universe's early expansion....
s. The largest known stellar black hole (as of 2007) is 15.65±1.45 solar masses. Additionally, there is evidence that the IC 10 X-1 X-ray source is a stellar black hole with a probable mass of 24-33 solar masses. As of April 2008, XTE J1650-500
XTE J1650-500
XTE J1650-500 is a stellar-mass black hole candidate and 2000-2001 transient binary X-ray source located in the constellation Ara.In 2008, it was claimed that this black hole had a mass of 3.8±0.5 solar masses, which would have been the smallest found for any black hole...
was reported by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
and others to be the smallest mass black hole currently known to science, with a mass 3.8 solar masses and a diameter of only 15 miles (24 kilometers).
There is observational evidence for two other types of black holes, which are much more massive than stellar black holes. They are intermediate-mass black hole
Intermediate-mass black hole
An Intermediate-mass black hole is a black hole whose mass is significantly more than stellar black holes yet far less than supermassive black holes...
s (in the centre of globular cluster
Globular cluster
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is...
s) and supermassive black hole
Supermassive black hole
A supermassive black hole is the largest type of black hole in a galaxy, in the order of hundreds of thousands to billions of solar masses. Most, and possibly all galaxies, including the Milky Way, are believed to contain supermassive black holes at their centers.Supermassive black holes have...
s in the centre of the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
and active galaxies.
X-ray compact binary systems
Stellar black holes in close binary systems are observable when matter is transferred from a companion star to the black hole. The energy release in the fall toward the compact star is so large that the matter heats up to temperatures of several hundred million degrees and radiates in X-rays (X-ray astronomyX-ray astronomy
X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects. X-radiation is absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and...
). The black hole therefore is observable in X-rays, whereas the companion star can be observed with optical telescopes. The energy release for black holes and neutron stars are of the same order of magnitude. Black holes and neutron stars are often difficult to distinguish.
However, neutron stars may have additional properties. They show differential rotation, and can have a magnetic field and exhibit localized explosions (thermonuclear bursts). Whenever such properties are observed, the compact object in the binary system is revealed as a neutron star.
The derived masses come from observations of compact X-ray sources (combining X-ray and optical data). All identified neutron stars have a mass below 3 to 5 solar masses. None of the compact systems with a mass above 5 solar masses reveals the properties of a neutron star. The combination of these facts make it more and more likely that the class of compact stars with a mass above 5 solar masses are in fact black holes.
Note that this proof of existence of stellar black holes is not entirely observational but relies on theory: We can think of no other object for these massive compact systems in stellar binaries than a black hole. A direct proof of the existence of a black hole would be if one actually observes the orbit of a particle (or a blob of gas) that falls into the black hole.
Candidates
Our Milky Way galaxy contains several stellar-mass Black Hole Candidates (BHCs) which are closer to us than the supermassive black hole in the Galactic center region. These candidates are all members of X-ray binaryX-ray binary
X-ray binaries are a class of binary stars that are luminous in X-rays.The X-rays are produced by matter falling from one component, called the donor to the other component, called the accretor, which is compact: a white dwarf, neutron star, or black hole.The infalling matter releases...
systems in which the compact object draws matter from its partner via an accretion disk. The probable black holes in these pairs range from three to more than a dozen solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
es.
| Name | BHC Black hole A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts 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... Mass (solar mass Solar mass The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies... es) |
Companion Mass (solar mass Solar mass The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies... es) |
Orbital period Orbital period The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of... (days) |
Distance from Earth (light years) | Location |
|---|---|---|---|---|---|
| A0620-00 A0620-00 A0620-00 is a binary star and black hole candidate in the constellation of Monoceros.-Evidence from observation:A0620-00 is a binary system consisting of a black hole with a mass roughly estimated to be 11.0±1.9 times the mass of Sun and a K-type star similar to sun with mass of approximately 1.5... /V616 Mon |
11 ± 2 | 2.6−2.8 | 0.33 | about 3500 | 06:22:44 -00:20:45 |
| GRO J1655-40 GRO J1655-40 |-! style="background-color: #FFFFC0;" colspan="2" | Astrometry|- style="vertical-align: top;"| Spectral type | F5IV|- style="vertical-align: top;"| Apparent magnitude | 17.0|- style="vertical-align: top;"| Distance | 5,500—11,000 ly... /V1033 Sco GRO J1655-40 |-! style="background-color: #FFFFC0;" colspan="2" | Astrometry|- style="vertical-align: top;"| Spectral type | F5IV|- style="vertical-align: top;"| Apparent magnitude | 17.0|- style="vertical-align: top;"| Distance | 5,500—11,000 ly... |
6.3 ± 0.3 | 2.6−2.8 | 2.8 | 5000−11000 | 16:54:00 -39:50:45 |
| XTE J1118+480/KV UMa | 6.8 ± 0.4 | 6−6.5 | 0.17 | 6200 | 11:18:11 +48:02:13 |
| Cyg X-1 Cygnus X-1 Cygnus X-1 is a well-known galactic X-ray source in the constellation Cygnus. It was discovered in 1964 during a rocket flight and is one of the strongest X-ray sources seen from Earth, producing a peak X-ray flux density of 2.3 Wm−2Hz−1... |
11 ± 2 | ≥18 | 5.6 | 6000−8000 | 19:58:22 +35:12:06 |
| GRO J0422+32 GRO J0422+32 GRO J0422+32 is an X-ray nova and black hole candidate that was discovered by the BATSE instrument on the CGRO satellite on 5 August 1992.During outburst, it was observed to be stronger than the Crab Nebula gamma-ray source out to photon energies of about 500 keV.The mass of the black hole in GRO... /V518 Per |
4 ± 1 | 1.1 | 0.21 | about 8500 | 04:21:43 +32:54:27 |
| GS 2000+25/QZ Vul | 7.5 ± 0.3 | 4.9−5.1 | 0.35 | about 8800 | 20:02:50 +25:14:11 |
| V404 Cyg | 12 ± 2 | 6.0 | 6.5 | about 10000 | 20:24:04 +33:52:03 |
| GX 339-4 GX 339-4 GX 339-4 is a moderately strong variable galactic Low-Mass X-ray binary source and black hole-candidate, which flares from time to time.-External Links:... /V821 Ara |
5−6 | 1.75 | about 15000 | 17:02:50 -48:47:23 | |
| GRS 1124-683 GRS 1124-683 The gamma-ray and X-ray source GRS 1124-683, discovered by the Granat mission and Ginga, is a system containing a black hole candidate. The system also goes by the name X-ray Nova Muscae 1991 or GU Mus... /GU Mus |
7.0 ± 0.6 | 0.43 | about 17000 | 11:26:27 -68:40:32 | |
| XTE J1550-564/V381 Nor | 9.6 ± 1.2 | 6.0−7.5 | 1.5 | about 17000 | 15:50:59 -56:28:36 |
| 4U 1543-475/IL Lupi | 9.4 ± 1.0 | 0.25 | 1.1 | about 24000 | 15:47:09 -47:40:10 |
| XTE J1819-254/V4641 Sgr V4641 Sgr V4641 Sagittarii is a variable X-ray binary star system in the constellation Sagittarius. It is the source of one of the fastest superluminal jets in our galaxy.... |
7.1 ± 0.3 | 5-8 | 2.82 | 24000 - 40000 | 18:19:22 -25:24:25 |
| GRS 1915+105 GRS 1915+105 GRS 1915+105 or V1487 Aquilae is an X-ray binary star system which features a regular star and a black hole. It was discovered on August 15, 1992 by the WATCH all-sky monitor aboard Granat. "GRS" stands for "GRANAT source", "1915" is the right ascension and "105" is declination in units of 0.1... /V1487 Aql |
14 ± 4.0 | ~1 | 33.5 | about 40000 | 19:15;12 +10:56:44 |
| XTE J1650-500 XTE J1650-500 XTE J1650-500 is a stellar-mass black hole candidate and 2000-2001 transient binary X-ray source located in the constellation Ara.In 2008, it was claimed that this black hole had a mass of 3.8±0.5 solar masses, which would have been the smallest found for any black hole... |
9.7 ± 1.6 | . | 0.32 | 16:50:01 -49:57:45 |
See also
- Black holeBlack holeA black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts 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...
Stellar-mass black hole candidates:
- Cygnus X-1Cygnus X-1Cygnus X-1 is a well-known galactic X-ray source in the constellation Cygnus. It was discovered in 1964 during a rocket flight and is one of the strongest X-ray sources seen from Earth, producing a peak X-ray flux density of 2.3 Wm−2Hz−1...
- GRO J1655-40GRO J1655-40|-! style="background-color: #FFFFC0;" colspan="2" | Astrometry|- style="vertical-align: top;"| Spectral type | F5IV|- style="vertical-align: top;"| Apparent magnitude | 17.0|- style="vertical-align: top;"| Distance | 5,500—11,000 ly...
- XTE J1650-500XTE J1650-500XTE J1650-500 is a stellar-mass black hole candidate and 2000-2001 transient binary X-ray source located in the constellation Ara.In 2008, it was claimed that this black hole had a mass of 3.8±0.5 solar masses, which would have been the smallest found for any black hole...
External links and further reading
- Black Holes: Gravity's Relentless Pull Award-winning interactive multimedia Web site about the physics and astronomy of black holes from the Space Telescope Science Institute
- Black hole diagrams
- Janusz Ziółkowski "Black Hole Candidates"
- Heaviest Stellar Black Hole Discovered in Nearby Galaxy, Newswise, 17-Oct-2007