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97-513: In the 1980s, the term hypernova was used to describe a theoretical type of supernova now known as a pair-instability supernova . It referred to the extremely high energy of the explosion compared to typical core collapse supernovae . The term had previously been used to describe hypothetical explosions from diverse events such as hyperstars , extremely massive population III stars in the early universe, or from events such as black hole mergers. In February 1997, Dutch-Italian satellite BeppoSAX

194-432: A neutron star is triggered to collapse into a black hole by the core collapse of a close companion consisting of a stripped carbon-oxygen core. The induced neutron star collapse allows for the formation of jets and high-energy ejecta that have been difficult to model from a single star. Pair-instability supernova A pair-instability supernova is a type of supernova predicted to occur when pair production ,

291-463: A November 1783 letter to Henry Cavendish , and in the early 20th century, physicists used the term "gravitationally collapsed object". Science writer Marcia Bartusiak traces the term "black hole" to physicist Robert H. Dicke , who in the early 1960s reportedly compared the phenomenon to the Black Hole of Calcutta , notorious as a prison where people entered but never left alive. The term "black hole"

388-428: A Schwarzschild black hole (i.e., non-rotating and not charged) cannot avoid being carried into the singularity once they cross the event horizon. They can prolong the experience by accelerating away to slow their descent, but only up to a limit. When they reach the singularity, they are crushed to infinite density and their mass is added to the total of the black hole. Before that happens, they will have been torn apart by

485-563: A Stationary System with Spherical Symmetry Consisting of Many Gravitating Masses", using his theory of general relativity to defend his argument. Months later, Oppenheimer and his student Hartland Snyder provided the Oppenheimer–Snyder model in their paper "On Continued Gravitational Contraction", which predicted the existence of black holes. In the paper, which made no reference to Einstein's recent publication, Oppenheimer and Snyder used Einstein's own theory of general relativity to show

582-506: A black hole appears to slow as it approaches the event horizon, taking an infinite amount of time to reach it. At the same time, all processes on this object slow down, from the viewpoint of a fixed outside observer, causing any light emitted by the object to appear redder and dimmer, an effect known as gravitational redshift . Eventually, the falling object fades away until it can no longer be seen. Typically this process happens very rapidly with an object disappearing from view within less than

679-597: A black hole can form an external accretion disk heated by friction , forming quasars , some of the brightest objects in the universe. Stars passing too close to a supermassive black hole can be shredded into streamers that shine very brightly before being "swallowed." If other stars are orbiting a black hole, their orbits can be used to determine the black hole's mass and location. Such observations can be used to exclude possible alternatives such as neutron stars. In this way, astronomers have identified numerous stellar black hole candidates in binary systems and established that

776-532: A black hole has formed, it can grow by absorbing mass from its surroundings. Supermassive black holes of millions of solar masses ( M ☉ ) may form by absorbing other stars and merging with other black holes, or via direct collapse of gas clouds . There is consensus that supermassive black holes exist in the centres of most galaxies . The presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as visible light. Any matter that falls toward

873-489: A black hole is the appearance of an event horizon—a boundary in spacetime through which matter and light can pass only inward towards the mass of the black hole. Nothing, not even light, can escape from inside the event horizon. The event horizon is referred to as such because if an event occurs within the boundary, information from that event cannot reach an outside observer, making it impossible to determine whether such an event occurred. As predicted by general relativity,

970-502: A black hole, as determined by the radius of the event horizon, or Schwarzschild radius, is proportional to the mass, M , through where r s is the Schwarzschild radius and M ☉ is the mass of the Sun . For a black hole with nonzero spin and/or electric charge, the radius is smaller, until an extremal black hole could have an event horizon close to The defining feature of

1067-458: A carbon-oxygen star lacking any significant hydrogen or helium, of type Ic supernovae was once thought to be an extremely evolved massive star, for example a type WO Wolf-Rayet star whose dense stellar wind expelled all its outer layers. Observations have failed to detect any such progenitors. It is still not conclusively shown that the progenitors are actually a different type of object, but several cases suggest that lower-mass "helium giants" are

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1164-458: A central object. In general relativity, however, there exists an innermost stable circular orbit (often called the ISCO), for which any infinitesimal inward perturbations to a circular orbit will lead to spiraling into the black hole, and any outward perturbations will, depending on the energy, result in spiraling in, stably orbiting between apastron and periastron, or escaping to infinity. The location of

1261-525: A certain limiting mass (now called the Chandrasekhar limit at 1.4  M ☉ ) has no stable solutions. His arguments were opposed by many of his contemporaries like Eddington and Lev Landau , who argued that some yet unknown mechanism would stop the collapse. They were partly correct: a white dwarf slightly more massive than the Chandrasekhar limit will collapse into a neutron star , which

1358-447: A different type at the end of their lives, but the causative mechanisms do not involve pair-instability. These stars are large enough to produce gamma rays with enough energy to create electron-positron pairs, but the resulting net reduction in counter-gravitational pressure is insufficient to cause the core-overpressure required for supernova. Instead, the contraction caused by pair-creation provokes increased thermonuclear activity within

1455-416: A generic prediction of general relativity. The discovery of neutron stars by Jocelyn Bell Burnell in 1967 sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality. The first black hole known was Cygnus X-1 , identified by several researchers independently in 1971. Black holes of stellar mass form when massive stars collapse at the end of their life cycle. After

1552-551: A gravitationally collapsed object, or black hole . The word "collapsar", short for "collapsed star ", was formerly used to refer to the end product of stellar gravitational collapse , a stellar-mass black hole . The word is now sometimes used to refer to a specific model for the collapse of a fast-rotating star. When core collapse occurs in a star with a core at least around fifteen times the Sun's mass ( M ☉ ) — though chemical composition and rotational rate are also significant —

1649-606: A metallicity Z between 0.02 and 0.001 may end their lives as pair-instability supernovae if their mass is in the appropriate range. Very large high-metallicity stars are probably unstable due to the Eddington limit , and would tend to shed mass during the formation process. Several sources describe the stellar behavior for large stars in pair-instability conditions. Gamma rays produced by stars of fewer than 100 or so solar masses are not energetic enough to produce electron-positron pairs. Some of these stars will undergo supernovae of

1746-431: A nebular remnant is produced and many solar masses of heavy elements are ejected into interstellar space. Some supernovae candidates for classification as pair-instability supernovae include: Black hole A black hole is a region of spacetime wherein gravity is so strong that no matter or electromagnetic energy (e.g. light ) can escape it. Albert Einstein 's theory of general relativity predicts that

1843-431: A non-rotating black hole, this region takes the shape of a single point; for a rotating black hole it is smeared out to form a ring singularity that lies in the plane of rotation. In both cases, the singular region has zero volume. It can also be shown that the singular region contains all the mass of the black hole solution. The singular region can thus be thought of as having infinite density . Observers falling into

1940-495: A second. On the other hand, indestructible observers falling into a black hole do not notice any of these effects as they cross the event horizon. According to their own clocks, which appear to them to tick normally, they cross the event horizon after a finite time without noting any singular behaviour; in classical general relativity, it is impossible to determine the location of the event horizon from local observations, due to Einstein's equivalence principle . The topology of

2037-419: A situation where quantum effects should describe these actions, due to the extremely high density and therefore particle interactions. To date, it has not been possible to combine quantum and gravitational effects into a single theory, although there exist attempts to formulate such a theory of quantum gravity . It is generally expected that such a theory will not feature any singularities. The photon sphere

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2134-415: A star is rotating slowly, then it will produce a faint supernova, but if the star is rotating quickly enough, then the fallback to the black hole will produce relativistic jets . Those powerful jets plough through stellar material produce strong shock waves, with the vigorous winds of newly-formed Ni blowing off the accretion disk, detonating the hypernova explosion. The ejected radioactive decay of Ni renders

2231-459: A stellar remnant behind. Pair-instability supernovae can only happen in stars with a mass range from around 130 to 250 solar masses and low to moderate metallicity (low abundance of elements other than hydrogen and helium – a situation common in Population III stars ). Photons given off by a body in thermal equilibrium have a black-body spectrum with an energy density proportional to

2328-487: A sufficiently compact mass can deform spacetime to form a black hole. The boundary of no escape is called the event horizon . A black hole has a great effect on the fate and circumstances of an object crossing it, but it has no locally detectable features according to general relativity. In many ways, a black hole acts like an ideal black body , as it reflects no light. Quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation , with

2425-423: A thermonuclear explosion. With more thermal energy released than the star's gravitational binding energy , it is completely disrupted; no black hole or other remnant is left behind. This is predicted to contribute to a " mass gap " in the mass distribution of stellar black holes . (This "upper mass gap" is to be distinguished from a suspected "lower mass gap" in the range of a few solar masses.) In addition to

2522-437: A typical core collapse supernova. The ejected nickel masses are large and the ejection velocity up to 99% of the speed of light . These are typically of type Ic, and some are associated with long-duration gamma-ray bursts . The electromagnetic energy released by these events varies from comparable to other type Ic supernova, to some of the most luminous supernovae known such as SN 1999as . The archetypal hypernova, SN 1998bw,

2619-432: Is a spherical boundary where photons that move on tangents to that sphere would be trapped in a non-stable but circular orbit around the black hole. For non-rotating black holes, the photon sphere has a radius 1.5 times the Schwarzschild radius. Their orbits would be dynamically unstable , hence any small perturbation, such as a particle of infalling matter, would cause an instability that would grow over time, either setting

2716-590: Is identical to that of any other body of the same mass. Solutions describing more general black holes also exist. Non-rotating charged black holes are described by the Reissner–Nordström metric , while the Kerr metric describes a non-charged rotating black hole. The most general stationary black hole solution known is the Kerr–Newman metric, which describes a black hole with both charge and angular momentum. While

2813-631: Is itself stable. In 1939, Robert Oppenheimer and others predicted that neutron stars above another limit, the Tolman–Oppenheimer–Volkoff limit , would collapse further for the reasons presented by Chandrasekhar, and concluded that no law of physics was likely to intervene and stop at least some stars from collapsing to black holes. Their original calculations, based on the Pauli exclusion principle , gave it as 0.7  M ☉ . Subsequent consideration of neutron-neutron repulsion mediated by

2910-517: Is likely to be a huge gas cloud being absorbed by a massive black hole. The event was also assigned the random name "ZTF20abrbeie" by the Zwicky Transient Facility . This name and the seeming ferocity of the event led to nickname "Scary Barbie", drawing the attention of the mainstream press. [1] Hypernovae are thought to be supernovae with ejecta having a kinetic energy larger than about 10  joule , an order of magnitude higher than

3007-454: Is not universally accepted. For very high-mass stars, with mass at least 130 and up to perhaps roughly 250 solar masses, a true pair-instability supernova can occur. In these stars, the first time that conditions support pair production instability, the situation runs out of control. The collapse proceeds to efficiently compress the star's core; the overpressure is sufficient to allow runaway nuclear fusion to burn it in several seconds, creating

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3104-543: Is taken from the rotational energy of the black hole. Thereby the rotation of the black hole slows down. A variation of the Penrose process in the presence of strong magnetic fields, the Blandford–Znajek process is considered a likely mechanism for the enormous luminosity and relativistic jets of quasars and other active galactic nuclei . In Newtonian gravity , test particles can stably orbit at arbitrary distances from

3201-409: Is the only vacuum solution that is spherically symmetric . This means there is no observable difference at a distance between the gravitational field of such a black hole and that of any other spherical object of the same mass. The popular notion of a black hole "sucking in everything" in its surroundings is therefore correct only near a black hole's horizon; far away, the external gravitational field

3298-414: Is the result of a process known as frame-dragging ; general relativity predicts that any rotating mass will tend to slightly "drag" along the spacetime immediately surrounding it. Any object near the rotating mass will tend to start moving in the direction of rotation. For a rotating black hole, this effect is so strong near the event horizon that an object would have to move faster than the speed of light in

3395-421: Is thought that rotation of the supernova progenitor drives a jet that accelerates material away from the explosion at close to the speed of light. Binary systems are increasingly being studied as the best method for both stripping stellar envelopes to leave a bare carbon-oxygen core, and for inducing the necessary spin conditions to drive a hypernova. The collapsar model describes a type of supernova that produces

3492-432: Is to form pairs of particles, such as electron-positron pairs, and these pairs can also meet and annihilate each other to create gamma rays again, all in accordance with Albert Einstein 's mass-energy equivalence equation E = m c ² . At the very high density of a large stellar core, pair production and annihilation occur rapidly. Gamma rays, electrons, and positrons are overall held in thermal equilibrium , ensuring

3589-669: The LIGO Scientific Collaboration and the Virgo collaboration announced the first direct detection of gravitational waves , representing the first observation of a black hole merger. On 10 April 2019, the first direct image of a black hole and its vicinity was published, following observations made by the Event Horizon Telescope (EHT) in 2017 of the supermassive black hole in Messier 87's galactic centre . As of 2023 ,

3686-425: The annihilation of the electron–positron pairs is insufficient to halt further contraction of the core. Finally, the thermal runaway ignites detonation fusion of oxygen and heavier elements. When the temperature reaches the level when electrons and positrons carry the same energy fraction as gamma-rays, pair production cannot increase any further, it is balanced by annihilation. Contraction no longer accelerates, but

3783-465: The gravitational field of a point mass and a spherical mass. A few months after Schwarzschild, Johannes Droste , a student of Hendrik Lorentz , independently gave the same solution for the point mass and wrote more extensively about its properties. This solution had a peculiar behaviour at what is now called the Schwarzschild radius , where it became singular , meaning that some of the terms in

3880-477: The stellar core are primarily in the form of very high-energy gamma rays . The pressure from these gamma rays fleeing outward from the core helps to hold up the upper layers of the star against the inward pull of gravity . If the level of gamma rays (the energy density ) is reduced, then the outer layers of the star will begin to collapse inwards. Gamma rays with sufficiently high energy can interact with nuclei, electrons, or one another. One of those interactions

3977-535: The 2020 Nobel Prize in Physics , Hawking having died in 2018. Based on observations in Greenwich and Toronto in the early 1970s, Cygnus X-1 , a galactic X-ray source discovered in 1964, became the first astronomical object commonly accepted to be a black hole. Work by James Bardeen , Jacob Bekenstein , Carter, and Hawking in the early 1970s led to the formulation of black hole thermodynamics . These laws describe

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4074-479: The Einstein equations became infinite. The nature of this surface was not quite understood at the time. In 1924, Arthur Eddington showed that the singularity disappeared after a change of coordinates. In 1933, Georges Lemaître realised that this meant the singularity at the Schwarzschild radius was a non-physical coordinate singularity . Arthur Eddington commented on the possibility of a star with mass compressed to

4171-401: The Kerr singularity, which leads to problems with causality like the grandfather paradox . It is expected that none of these peculiar effects would survive in a proper quantum treatment of rotating and charged black holes. The appearance of singularities in general relativity is commonly perceived as signalling the breakdown of the theory. This breakdown, however, is expected; it occurs in

4268-415: The Schwarzschild radius in a 1926 book, noting that Einstein's theory allows us to rule out overly large densities for visible stars like Betelgeuse because "a star of 250 million km radius could not possibly have so high a density as the Sun. Firstly, the force of gravitation would be so great that light would be unable to escape from it, the rays falling back to the star like a stone to the earth. Secondly,

4365-664: The Schwarzschild solution for the future of observers falling into a black hole. A complete extension had already been found by Martin Kruskal , who was urged to publish it. These results came at the beginning of the golden age of general relativity , which was marked by general relativity and black holes becoming mainstream subjects of research. This process was helped by the discovery of pulsars by Jocelyn Bell Burnell in 1967, which, by 1969, were shown to be rapidly rotating neutron stars. Until that time, neutron stars, like black holes, were regarded as just theoretical curiosities; but

4462-463: The behaviour of a black hole in close analogy to the laws of thermodynamics by relating mass to energy, area to entropy , and surface gravity to temperature . The analogy was completed when Hawking, in 1974, showed that quantum field theory implies that black holes should radiate like a black body with a temperature proportional to the surface gravity of the black hole, predicting the effect now known as Hawking radiation . On 11 February 2016,

4559-498: The black hole horizon, including approximately conserved quantum numbers such as the total baryon number and lepton number . This behaviour is so puzzling that it has been called the black hole information loss paradox . The simplest static black holes have mass but neither electric charge nor angular momentum. These black holes are often referred to as Schwarzschild black holes after Karl Schwarzschild who discovered this solution in 1916. According to Birkhoff's theorem , it

4656-405: The common types of supernova. The light curves are highly extended, with peak luminosity occurring months after onset. This is due to the extreme amounts of Ni expelled, and the optically dense ejecta, as the star is entirely disrupted. Pair-instability supernovae completely destroy the progenitor star and do not leave behind a neutron star or black hole. The entire mass of the star is ejected, so

4753-434: The conditions on how a black hole could develop, for the first time in contemporary physics. 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". This did not strictly contradict Oppenheimer's results, but extended them to include the point of view of infalling observers. Finkelstein's solution extended

4850-436: The core now produces much more energy than prior to collapse, and this results in a supernova: the outer layers of the star are blown away by sudden large increase of power production in the core. Calculations suggest that so much of the outer layers are lost that the very hot core itself is no longer under sufficient pressure to keep it intact, and it is completely disrupted too. For a star to undergo pair-instability supernova,

4947-448: 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. In this period more general black hole solutions were found. In 1963, Roy Kerr found the exact solution for a rotating black hole . Two years later, Ezra Newman found the axisymmetric solution for a black hole that is both rotating and electrically charged . Through

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5044-400: The event horizon of a black hole at equilibrium is always spherical. For non-rotating (static) black holes the geometry of the event horizon is precisely spherical, while for rotating black holes the event horizon is oblate. At the centre of a black hole, as described by general relativity, may lie a gravitational singularity , a region where the spacetime curvature becomes infinite. For

5141-616: The excess energy from the earlier stages before the runaway fusion can cause a hypernova explosion; the star then collapses completely into a black hole. Pair-instability supernovae are popularly thought to be highly luminous. This is only the case for the most massive progenitors since the luminosity depends strongly on the ejected mass of radioactive Ni. They can have peak luminosities of over 10 W, brighter than type Ia supernovae, but at lower masses peak luminosities are less than 10 W, comparable to or less than typical type II supernovae. The spectra of pair-instability supernovae depend on

5238-403: The expanding supernova's core pressure drops. As temperatures and gamma ray energies increase, more and more gamma ray energy is absorbed in creating electron–positron pairs. This reduction in gamma ray energy density reduces the radiation pressure that resists gravitational collapse and supports the outer layers of the star. The star contracts, compressing and heating the core, thereby increasing

5335-414: The explosion energy is insufficient to expel the outer layers of the star, and it will collapse into a black hole without producing a visible supernova outburst. A star with a core mass slightly below this level — in the range of 5–15  M ☉ — will undergo a supernova explosion, but so much of the ejected mass falls back onto the core remnant that it still collapses into a black hole. If such

5432-423: The first modern solution of general relativity that would characterise a black hole. Due to his influential research, the Schwarzschild metric is named after him. David Finkelstein , in 1958, first published the interpretation of "black hole" as a region of space from which nothing can escape. Black holes were long considered a mathematical curiosity; it was not until the 1960s that theoretical work showed they were

5529-506: The fourth power of the temperature, as described by the Stefan–Boltzmann law . Wien's law states that the wavelength of maximum emission from a black body is inversely proportional to its temperature. Equivalently, the frequency, and the energy, of the peak emission is directly proportional to the temperature. In very massive, hot stars with interior temperatures above about 300 000 000   K ( 3 × 10  K ), photons produced in

5626-648: The growing tidal forces in a process sometimes referred to as spaghettification or the "noodle effect". In the case of a charged (Reissner–Nordström) or rotating (Kerr) black hole, it is possible to avoid the singularity. Extending these solutions as far as possible reveals the hypothetical possibility of exiting the black hole into a different spacetime with the black hole acting as a wormhole . The possibility of travelling to another universe is, however, only theoretical since any perturbation would destroy this possibility. It also appears to be possible to follow closed timelike curves (returning to one's own past) around

5723-414: The high-energy ejecta that characterises them as hypernovae. Unusually bright radio supernovae have been observed as counterparts to hypernovae, and have been termed "radio hypernovae". Models for hypernova focus on the efficient transfer of energy into the ejecta. In normal core collapse supernovae , 99% of neutrinos generated in the collapsing core escape without driving the ejection of material. It

5820-402: The immediate energy release, a large fraction of the star's core is transformed to nickel-56 , a radioactive isotope which decays with a half-life of 6.1 days into cobalt-56 . Cobalt-56 has a half-life of 77 days and then further decays to the stable isotope iron-56 (see Supernova nucleosynthesis ). For the hypernova SN 2006gy , studies indicate that perhaps 40 solar masses of

5917-484: The increased creation of positron/electron pairs by gamma ray collisions must reduce outward pressure enough for inward gravitational pressure to overwhelm it. High rotational speed and/or metallicity can prevent this. Stars with these characteristics still contract as their outward pressure drops, but unlike their slower or less metal-rich cousins, these stars continue to exert enough outward pressure to prevent gravitational collapse. Stars formed by collision mergers having

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6014-491: The late 20th century has since been refined to refer to those supernovae with unusually large kinetic energy. The first hypernova observed was SN 1998bw , with a luminosity 100 times higher than a standard Type Ib. This supernova was the first to be associated with a gamma-ray burst (GRB) and it produced a shockwave containing an order of magnitude more energy than a normal supernova. Other scientists prefer to call these objects simply broad-lined type Ic supernovae . Since then

6111-544: The mass of a black hole can take any positive value, the charge and angular momentum are constrained by the mass. The total electric charge  Q and the total angular momentum  J are expected to satisfy the inequality for a black hole of mass M . Black holes with the minimum possible mass satisfying this inequality are called extremal . Solutions of Einstein's equations that violate this inequality exist, but they do not possess an event horizon. These solutions have so-called naked singularities that can be observed from

6208-414: The microscopic level, because they are time-reversible . Because a black hole eventually achieves a stable state with only three parameters, there is no way to avoid losing information about the initial conditions: the gravitational and electric fields of a black hole give very little information about what went in. The information that is lost includes every quantity that cannot be measured far away from

6305-411: The nature of the progenitor star. Thus they can appear as type II or type Ib/c supernova spectra. Progenitors with a significant remaining hydrogen envelope will produce a type II supernova, those with no hydrogen but significant helium will produce a type Ib, and those with no hydrogen and virtually no helium will produce a type Ic. In contrast to the spectra, the light curves are quite different from

6402-474: The nearest known body thought to be a black hole, Gaia BH1 , is around 1,560 light-years (480 parsecs ) away. Though only a couple dozen black holes have been found so far in the Milky Way, there are thought to be hundreds of millions, most of which are solitary and do not cause emission of radiation. Therefore, they would only be detectable by gravitational lensing . John Michell used the term "dark star" in

6499-503: The opposite direction to just stand still. The ergosphere of a black hole is a volume bounded by the black hole's event horizon and the ergosurface , which coincides with the event horizon at the poles but is at a much greater distance around the equator. Objects and radiation can escape normally from the ergosphere. Through the Penrose process , objects can emerge from the ergosphere with more energy than they entered with. The extra energy

6596-418: The original star were released as Ni-56, almost the entire mass of the star's core regions. Collision between the exploding star core and gas it ejected earlier, and radioactive decay, release most of the visible light. A different reaction mechanism, photodisintegration , follows the initial pair-instability collapse in stars of at least 250 solar masses. This endothermic (energy-absorbing) reaction absorbs

6693-425: The outside, and hence are deemed unphysical . The cosmic censorship hypothesis rules out the formation of such singularities, when they are created through the gravitational collapse of realistic matter . This is supported by numerical simulations. Due to the relatively large strength of the electromagnetic force , black holes forming from the collapse of stars are expected to retain the nearly neutral charge of

6790-418: The photon on an outward trajectory causing it to escape the black hole, or on an inward spiral where it would eventually cross the event horizon. While light can still escape from the photon sphere, any light that crosses the photon sphere on an inbound trajectory will be captured by the black hole. Hence any light that reaches an outside observer from the photon sphere must have been emitted by objects between

6887-399: The photon sphere and the event horizon. For a Kerr black hole the radius of the photon sphere depends on the spin parameter and on the details of the photon orbit, which can be prograde (the photon rotates in the same sense of the black hole spin) or retrograde. Rotating black holes are surrounded by a region of spacetime in which it is impossible to stand still, called the ergosphere. This

6984-458: The presence of a mass deforms spacetime in such a way that the paths taken by particles bend towards the mass. At the event horizon of a black hole, this deformation becomes so strong that there are no paths that lead away from the black hole. To a distant observer, clocks near a black hole would appear to tick more slowly than those farther away from the black hole. Due to this effect, known as gravitational time dilation , an object falling into

7081-450: The production of free electrons and positrons in the collision between atomic nuclei and energetic gamma rays , temporarily reduces the internal radiation pressure supporting a supermassive star 's core against gravitational collapse . This pressure drop leads to a partial collapse, which in turn causes greatly accelerated burning in a runaway thermonuclear explosion, resulting in the star being blown completely apart without leaving

7178-417: The progenitors. These stars are not sufficiently massive to expel their envelopes simply by stellar winds, and they would be stripped by mass transfer to a binary companion. Helium giants are increasingly favoured as the progenitors of type Ib supernovae, but the progenitors of type Ic supernovae is still uncertain. One proposed mechanism for producing gamma-ray bursts is induced gravitational collapse , where

7275-509: The radio source known as Sagittarius A* , at the core of the Milky Way galaxy, contains a supermassive black hole of about 4.3 million solar masses. The idea of a body so big that even light could not escape was briefly proposed by English astronomical pioneer and clergyman John Michell in a letter published in November 1784. Michell's simplistic calculations assumed such a body might have

7372-426: The rate of energy production. This increases the energy of the gamma rays that are produced, making them more likely to interact, and so increases the rate at which energy is absorbed in further pair production. As a result, the stellar core loses its support in a runaway process, in which gamma rays are created at an increasing rate; but more and more of the gamma rays are absorbed to produce electron–positron pairs, and

7469-403: The red shift of the spectral lines would be so great that the spectrum would be shifted out of existence. Thirdly, the mass would produce so much curvature of the spacetime metric that space would close up around the star, leaving us outside (i.e., nowhere)." In 1931, Subrahmanyan Chandrasekhar calculated, using special relativity, that a non-rotating body of electron-degenerate matter above

7566-506: The same density as the Sun, and concluded that one would form when a star's diameter exceeds the Sun's by a factor of 500, and its surface escape velocity exceeds the usual speed of light. Michell correctly noted that such supermassive but non-radiating bodies might be detectable through their gravitational effects on nearby visible bodies. Scholars of the time were initially excited by the proposal that giant but invisible 'dark stars' might be hiding in plain view, but enthusiasm dampened when

7663-430: The same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the order of billionths of a kelvin for stellar black holes , making it essentially impossible to observe directly. Objects whose gravitational fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace . In 1916, Karl Schwarzschild found

7760-414: The same values for these properties, or parameters, are indistinguishable from one another. The degree to which the conjecture is true for real black holes under the laws of modern physics is currently an unsolved problem. These properties are special because they are visible from outside a black hole. For example, a charged black hole repels other like charges just like any other charged object. Similarly,

7857-478: The shape of the object or distribution of charge on it is evenly distributed along the horizon of the black hole, and is lost to outside observers. The behaviour of the horizon in this situation is a dissipative system that is closely analogous to that of a conductive stretchy membrane with friction and electrical resistance —the membrane paradigm . This is different from other field theories such as electromagnetism, which do not have any friction or resistivity at

7954-406: The singularities would not appear in generic situations. This view was held in particular by Vladimir Belinsky , Isaak Khalatnikov , and Evgeny Lifshitz , who tried to prove that no singularities appear in generic solutions. However, in the late 1960s Roger Penrose and Stephen Hawking used global techniques to prove that singularities appear generically. For this work, Penrose received half of

8051-429: The star that repulses the inward pressure and returns the star to equilibrium. It is thought that stars of this size undergo a series of these pulses until they shed sufficient mass to drop below 100 solar masses, at which point they are no longer hot enough to support pair-creation. Pulsing of this nature may have been responsible for the variations in brightness experienced by Eta Carinae in 1843 , though this explanation

8148-415: The star's core remains stable. By random fluctuation, the sudden heating and compression of the core can generate gamma rays energetic enough to be converted into an avalanche of electron-positron pairs. This reduces the pressure. When the collapse stops, the positrons find electrons and the pressure from gamma rays is driven up, again. The population of positrons provides a brief reservoir of new gamma rays as

8245-460: The star's surface. Instead, spacetime itself is curved such that the geodesic that light travels on never leaves the surface of the "star" (black hole). In 1915, Albert Einstein developed his theory of general relativity , having earlier shown that gravity does influence light's motion. Only a few months later, Karl Schwarzschild found a solution to the Einstein field equations that describes

8342-436: The star. Rotation, however, is expected to be a universal feature of compact astrophysical objects. The black-hole candidate binary X-ray source GRS 1915+105 appears to have an angular momentum near the maximum allowed value. That uncharged limit is allowing definition of a dimensionless spin parameter such that Black holes are commonly classified according to their mass, independent of angular momentum, J . The size of

8439-480: The strong force raised the estimate to approximately 1.5  M ☉ to 3.0  M ☉ . Observations of the neutron star merger GW170817 , which is thought to have generated a black hole shortly afterward, have refined the TOV limit estimate to ~2.17  M ☉ . Oppenheimer and his co-authors interpreted the singularity at the boundary of the Schwarzschild radius as indicating that this

8536-432: The term for its brevity and "advertising value", and it quickly caught on, leading some to credit Wheeler with coining the phrase. The no-hair theorem postulates that, once it achieves a stable condition after formation, a black hole has only three independent physical properties: mass, electric charge, and angular momentum; the black hole is otherwise featureless. If the conjecture is true, any two black holes that share

8633-418: The term has been applied to a variety of objects, not all of which meet the standard definition; for example ASASSN-15lh . In 2023, the observation of the highly energetic, non-quasar transient event AT2021lwx was published with an extremely strong emission from mid-infrared to X-ray wavelengths and an overall energy of 1.5 10  Joule . This object is not thought to be a hypernova; instead, it

8730-518: The total mass inside a sphere containing a black hole can be found by using the gravitational analogue of Gauss's law (through the ADM mass ), far away from the black hole. Likewise, the angular momentum (or spin) can be measured from far away using frame dragging by the gravitomagnetic field , through for example the Lense–Thirring effect . When an object falls into a black hole, any information about

8827-419: The visible outburst substantially more luminous than a standard supernova. The jets also beam high energy particles and gamma rays directly outward and thereby produce x-ray or gamma-ray bursts; the jets can last for several seconds or longer and correspond to long-duration gamma-ray bursts, but they do not appear to explain short-duration gamma-ray bursts. The mechanism for producing the stripped progenitor,

8924-446: The wavelike nature of light became apparent in the early nineteenth century, as if light were a wave rather than a particle, it was unclear what, if any, influence gravity would have on escaping light waves. The modern theory of gravity, general relativity, discredits Michell's notion of a light ray shooting directly from the surface of a supermassive star, being slowed down by the star's gravity, stopping, and then free-falling back to

9021-484: The work of Werner Israel , Brandon Carter , and David Robinson the no-hair theorem emerged, stating that a stationary black hole solution is completely described by the three parameters of the Kerr–Newman metric : mass , angular momentum , and electric charge. At first, it was suspected that the strange features of the black hole solutions were pathological artefacts from the symmetry conditions imposed, and that

9118-470: Was able to trace GRB 970508 to a faint galaxy roughly 6 billion light years away. From analyzing the spectroscopic data for both the GRB 970508 and its host galaxy, Bloom et al. concluded in 1998 that a hypernova was the likely cause. That same year, hypernovae were hypothesized in greater detail by Polish astronomer Bohdan Paczyński as supernovae from rapidly spinning stars. The usage of the term hypernova from

9215-503: Was associated with GRB 980425 . Its spectrum showed no hydrogen and no clear helium features, but strong silicon lines identified it as a type Ic supernova. The main absorption lines were extremely broadened and the light curve showed a very rapid brightening phase, reaching the brightness of a type Ia supernova at day 16. The total ejected mass was about 10  M ☉ and the mass of nickel ejected about 0.4  M ☉ . All supernovae associated with GRBs have shown

9312-451: Was the boundary of a bubble in which time stopped. This is a valid point of view for external observers, but not for infalling observers. The hypothetical collapsed stars were called "frozen stars", because an outside observer would see the surface of the star frozen in time at the instant where its collapse takes it to the Schwarzschild radius. Also in 1939, Einstein attempted to prove that black holes were impossible in his publication "On

9409-632: Was used in print by Life and Science News magazines in 1963, and by science journalist Ann Ewing in her article " 'Black Holes' in Space", dated 18 January 1964, which was a report on a meeting of the American Association for the Advancement of Science held in Cleveland, Ohio. In December 1967, a student reportedly suggested the phrase "black hole" at a lecture by John Wheeler ; Wheeler adopted

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