Simulated view of a black hole in front of the Milky Way. The hole has 10 solar masses and is viewed from a distance of 600 km. An acceleration of about 400 million g is necessary to sustain this distance constantly.^[1]

General relativity

Key topics

Introduction to... Mathematical formulation of...

Fundamental concepts

Special relativity Equivalence principle World line · Riemannian geometry

Phenomena

Kepler problem · Lenses · Waves Frame-dragging · Geodetic effect Event horizon · Singularity Black hole A black hole is an object with sufficient density that the force of gravity prevents anything from escaping from it except through quantum tunneling behavior. ... Image File history File links Download high resolution version (2560x2048, 1172 KB) Summary Description: A Black Hole of ten solar masses as seen from a distance of 600km with the Milky Way in the background (horizontal camera opening angle: 90°) Source: Gallery of Tempolimit Lichtgeschwindigkeit Date: 14. ... Image File history File links Download high resolution version (2560x2048, 1172 KB) Summary Description: A Black Hole of ten solar masses as seen from a distance of 600km with the Milky Way in the background (horizontal camera opening angle: 90°) Source: Gallery of Tempolimit Lichtgeschwindigkeit Date: 14. ... The term g force or gee force refers to the symbol g, the force of acceleration due to gravity at the earths surface. ... For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ... Newton’s conception and quantification of gravitation held until the beginning of the 20th century, when Albert Einstein extended the special relativity to form the general relativity (GR) theory. ... For a less technical introduction to this topic, please see Introduction to mathematics of general relativity. ... For a less technical and generally accessible introduction to the topic, see Introduction to special relativity. ... In the physics of relativity, the equivalence principle is applied to several related concepts dealing with gravitation and the uniformity of physical measurements in different frames of reference. ... In physics, the world line of an object is the unique path of that object as it travels through 4-dimensional spacetime. ... In differential geometry, Riemannian geometry is the study of smooth manifolds with Riemannian metrics, i. ... In general relativity, the Kepler problem involves solving for the motion of a particle of negligible mass in the external gravitational field of another body of mass M. This gravitational field is described by the Schwarzschild solution to the vacuum Einstein equations of general relativity, and particle motion is described... This article or section is in need of attention from an expert on the subject. ... In physics, a gravitational wave is a fluctuation in the curvature of spacetime which propagates as a wave, traveling outward from a moving object or system of objects. ... According to Albert Einsteins theory of general relativity, space and time get pulled out of shape near a rotating body in a phenomenon referred to as frame-dragging. ... The geodetic effect represents the effect of the curvature of spacetime, predicted by general relativity, on a spinning, moving body. ... For the science fiction film, see Event Horizon (film). ... A gravitational singularity (sometimes spacetime singularity) is, approximately, a place where quantities which are used to measure the gravitational field become infinite. ...

Equations

Linearized Gravity Post-Newtonian formalism Einstein field equations

Advanced theories

Kaluza-Klein Quantum gravity

Solutions

Schwarzschild Reissner-Nordström · Gödel Kerr · Kerr-Newman Kasner · Milne · Robertson-Walker It has been suggested that Weak-field approximation be merged into this article or section. ... The parameterized post-Newtonian formalism or PPN formalism is a tool used to compare classical theories of gravitation in the limit most important for everyday gravitational experiments: the limit in which the gravitational field is weak and generated by objects moving slowly compared to the speed of light. ... The Einstein field equations (EFE) or Einsteins equations are a set of ten equations in Einsteins theory of general relativity in which the fundamental force of gravitation is described as a curved spacetime caused by matter and energy. ... Kaluza-Klein theory (or KK theory, for short) is a model which sought to unify classical gravity and electromagnetism. ... This article does not cite any references or sources. ... It has been suggested that Deriving the Schwarzschild solution be merged into this article or section. ... In physics and astronomy, a Reissner-Nordström black hole, discovered by Gunnar Nordström and Hans Reissner, is a black hole that carries electric charge , no angular momentum, and mass . ... The Gödel solution is an exact solution of the Einstein field equation in which the stress-energy tensor contains two terms, the first representing the matter density of a homogeneous distribution of swirling dust particles, and the second associated with a nonzero cosmological constant (see lambdavacuum solution). ... In general relativity, the Kerr metric (or Kerr vacuum) describes the geometry of spacetime around a rotating massive body, such as a rotating black hole. ... The Kerr-Newman metric is a solution of Einsteins general relativity field equation that describes the spacetime geometry around a charged (), rotating () black hole of mass m. ... The Kasner metric is an exact solution to Einsteins theory of general relativity. ... Milnes model follows the description from special relativity of an observable universes spacetime diagram containing past and future light cones along with elsewhere in spacetime. ... // The Friedmann-Lemaître-Robertson-Walker (FLRW) metric is an exact solution of the Einstein field equations of general relativity and which describes a homogeneous, isotropic expanding/contracting universe. ...

Scientists

Einstein · Minkowski · Eddington Lemaître · Schwarzschild Robertson · Kerr · Friedman Chandrasekhar · Hawking · others “Einstein” redirects here. ... Hermann Minkowski. ... One of Sir Arthur Stanley Eddingtons papers announced Einsteins theory of general relativity to the English-speaking world. ... Father Georges-Henri Lemaître (July 17, 1894 – June 20, 1966) was a Belgian Roman Catholic priest, honorary prelate, professor of physics and astronomer. ... Karl Schwarzschild (October 9, 1873 - May 11, 1916) was a noted German Jewish physicist and astronomer, father of astrophysicist Martin Schwarzschild. ... Howard Percy Robertson (January 27, 1903 - August 26, 1961) was a scientist known for contributions related to cosmology and the uncertainty principle. ... Roy Patrick Kerr (1934- ) is a New Zealand born mathematician who is best known for discovering the famous Kerr vacuum, an exact solution to the Einstein field equation of general relativity, which models the gravitational field outside an uncharged rotating massive object, or even a rotating black hole. ... Alexander Alexandrovich Friedman or Friedmann (Александр Александрович Фридман) (June 16, 1888 – September 16, 1925) was a Russian cosmologist and mathematician. ... Chandrasekhar redirects here. ... Stephen William Hawking, CH, CBE, FRS, FRSA, (born 8 January 1942) is a British theoretical physicist. ... This is a partial list of persons who have made major contributions to the development of standard mainstream general relativity. ...

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A black hole is a region of space whose gravitational field is so powerful that nothing can escape it once it has fallen past a certain point, called the event horizon. The name comes from the fact that even electromagnetic radiation (i.e. light) is unable to escape, rendering the interior invisible. However, black holes can be detected if they interact with matter outside the event horizon, for example by drawing in gas from an orbiting star. The gas spirals inward, heating up to very high temperatures and emitting large amounts of radiation in the process.^[2][3][4] A gravitational field is a model used within physics to explain how gravity exists in the universe. ... For the science fiction film, see Event Horizon (film). ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... This article does not cite any references or sources. ... Radiation as used in physics, is energy in the form of waves or moving subatomic particles. ...

While the idea of an object with gravity strong enough to prevent light from escaping was proposed in the 18th century, black holes as presently understood are described by Einstein's theory of general relativity, developed in 1916. This theory predicts that when a large enough amount of mass is present within a sufficiently small region of space, all paths through space are warped inwards towards the center of the volume, forcing all matter and radiation to fall inwardly. Gravity is a force of attraction that acts between bodies that have mass. ... Einstein redirects here. ... For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ... This article or section is in need of attention from an expert on the subject. ... The hoop conjecture was proposed by Kip Thorne in 1972. ... In physics, the world line of an object is the unique path of that object as it travels through 4-dimensional spacetime. ...

While general relativity describes a black hole as a region of empty space with a pointlike singularity at the center and an event horizon at the outer edge, the description changes when the effects of quantum mechanics are taken into account. Research on this subject indicates that, rather than holding captured matter forever, black holes slowly leak a form of thermal energy called Hawking radiation.^[5][6][7] However, the final, correct description of black holes, requiring a theory of quantum gravity, is unknown. A gravitational singularity (sometimes spacetime singularity) is, approximately, a place where quantities which are used to measure the gravitational field become infinite. ... Fig. ... In physics, Hawking radiation (also known as Bekenstein-Hawking radiation) is a thermal radiation thought to be emitted by black holes due to quantum effects. ... This article does not cite any references or sources. ...

Sizes of black holes

Black holes can have any mass. Since gravity increases in inverse proportion to volume, any quantity of matter that is sufficiently compressed will become a black hole. However, when black holes form naturally, only a few mass ranges are realistic. This article is about matter in physics and chemistry. ...

Black holes can be divided into several size categories:

• Supermassive black holes that contain millions to billions of times the mass of the sun are believed to exist in the center of most galaxies, including our own Milky Way.
• Intermediate-mass black holes, whose size is measured in thousands of solar masses, may exist. Intermediate-mass black holes have been proposed as a possible power source for ultra-luminous X ray sources.
• Stellar-mass black holes have masses ranging from about 1.5-3.0 solar masses (the Tolman-Oppenheimer-Volkoff limit) to 15 solar masses. These black holes are created by the collapse of individual stars. Stars above about 20 solar masses may collapse to form black holes; the cores of lighter stars form neutron stars or white dwarf stars. In all cases some of the star's material is lost (blown away during the red giant stage for stars that turn into white dwarfs, or lost in a supernova explosion for stars that turn into neutron stars or black holes). NB: Supernovae Can Only Occur With Red Supergiants
• Micro black holes, which have masses at which the effects of quantum mechanics are expected to become very important. This is usually assumed to be near the Planck mass. Alternatively, the term micro black hole or mini black hole may refer to any black hole with mass much less than that of a star. Black holes of this type have been proposed to have formed during the Big Bang (primordial black holes), but no such holes have been detected as of 2007.

Astrophysicists expect to find stellar-mass and larger black holes, because a stellar mass black hole is formed by the gravitational collapse of a star of 20 or more solar masses at the end of its life, and can then act as a seed for the formation of a much larger black hole. Top: artists conception of a supermassive black hole drawing material from a nearby star. ... In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ... For the confectionery, see Milky Way bar. ... An Intermediate-mass black hole (IMBH) is a black hole whose mass is significantly more than stellar black holes (a few tens of the mass of Sun) yet far less than supermassive black holes (a few millions of the mass of Sun). ... An ultra-luminous X-ray source (ULX) is an astronomical source of X-rays that is not in the nucleus of a galaxy, and is more luminous than erg/s, assuming that it radiates isotropically. ... A stellar black hole is a black hole formed by the gravitational collapse of a massive star (3 or more solar masses) at the end of its lifetime. ... This article is in need of attention from an expert on the subject. ... For the Hugo Award-winning story by Larry Niven, see Neutron Star (story). ... This article or section does not adequately cite its references or sources. ... According to the Hertzsprung-Russell diagram, a red giant is a large non-main sequence star of stellar classification K or M; so-named because of the reddish appearance of the cooler giant stars. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... This article or section is in need of attention from an expert on the subject. ... Fig. ... The Planck mass is the natural unit of mass, denoted by mP. It is the mass for which the Schwarzschild radius is equal to the Compton length divided by π. ≈ 1. ... For other uses, see Big Bang (disambiguation). ... A black hole concept drawing by NASA A primordial black hole is a hypothetical type of black hole that is formed not by the gravitational collapse of a star but by the extreme density of matter present during the universes early expansion. ... 2007 is a common year starting on Monday of the Gregorian calendar. ... This article or section does not cite its references or sources. ...

Micro black holes might be produced by:

• The Big Bang, which produced pressures far larger than that of a supernova and therefore sufficient to produce primordial black holes without needing the powerful gravity fields of collapsing large stars.
• High-energy particle accelerators such as the Large Hadron Collider (LHC), if certain non-standard assumptions are correct (typically, an assumption of large extra dimensions). However, any black holes produced in such a manner will evaporate practically instantaneously, thus posing no danger to Earth.

A black hole is defined by the velocity that would have to be attained to escape from its gravitational pull, which is termed the escape velocity. Within some distance from a black hole, this velocity would be greater than the speed of light - in other words infinite energy would be required to accelerate away from the black hole. For example, the escape velocity of the Earth at the surface is equal to 11 km/s. For an object to escape the Earth's gravitational pull at the surface without applying additional energy (i.e. unpowered), ignoring the effects of drag, it must go at least 11 km/s, regardless of its mass or density. On the other hand, the escape velocity at the surface of a gravitational body is related to its density - the ratio of its mass to radius - since the velocity required diminishes as one moves away from the center of mass. It is theoretically possible for objects with very small masses to be so dense that light couldn't escape, within a correspondingly small radius, however black holes are usually postulated as objects on the scale of the mass of stars or much greater. For other uses, see Big Bang (disambiguation). ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... A black hole concept drawing by NASA A primordial black hole is a hypothetical type of black hole that is formed not by the gravitational collapse of a star but by the extreme density of matter present during the universes early expansion. ... A particle accelerator uses electric fields to propel charged particles to great energies. ... The Large Hadron Collider (LHC) is a particle accelerator and collider located at CERN, near Geneva, Switzerland (). Currently under construction, the LHC is scheduled to begin operation in May 2008. ... In particle physics, the ADD model, also known as the model with old large dimensions, is a scenario inspired by string theory to explain the weakness of gravity relatively to other forces in which the fields of the Standard Model are confined to a higher-dimensional membrane but gravity can... Kaluza-Klein theory (or KK theory, for short) is a model which sought to unify classical gravity and electromagnetism. ... For other uses, see Black hole (disambiguation). ... Space Shuttle Atlantis launches on mission STS-71. ... “Lightspeed” redirects here. ... This article is about Earth as a planet. ... An object falling through a gas or liquid experiences a force in direction opposite to its motion. ...

What makes it impossible to escape from black holes?

General relativity describes mass as changing the shape of spacetime, and the shape of spacetime as describing how matter moves through space. For objects much less dense than black holes, this results in something similar to Newton's laws of gravity: objects with mass attract each other, but it's possible to define an escape velocity which allows a test object to leave the gravitational field of any large object. For objects as dense as black holes, this stops being the case. The effort required to leave the hole becomes infinite, with no escape velocity defined. For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ... This article or section is in need of attention from an expert on the subject. ... For other uses of this term, see Spacetime (disambiguation). ... Isaac Newtons theory of universal gravitation (part of classical mechanics) states the following: Every single point mass attracts every other point mass by a force pointing along the line combining the two. ... Space Shuttle Atlantis launches on mission STS-71. ...

There are several ways of describing the situation that causes escape to be impossible. The difference between these descriptions is how space and time coordinates are drawn on spacetime (the choice of coordinates depends on the choice of observation point and on additional definitions used). One common description, based on the Schwarzschild description of black holes, is to consider the time axis in spacetime to point inwards towards the center of the black hole once the horizon is crossed.^[8] Under these conditions, falling further into the hole is as inevitable as moving forward in time. A related description is to consider the future light cone of a test object near the hole (all possible paths the object or anything emitted by it could take, limited by the speed of light). As the object approaches the event horizon at the boundary of the black hole, the future light cone tilts inwards towards the horizon. When the test object passes the horizon, the cone tilts completely inward, and all possible paths lead into the hole.^[9] Space has been an interest for philosophers and scientists for much of human history. ... A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ... For other uses of this term, see Spacetime (disambiguation). ... It has been suggested that Deriving the Schwarzschild solution be merged into this article or section. ... In special relativity, a light cone is the pattern describing the temporal evolution of a flash of light in Minkowski spacetime. ... “Lightspeed” redirects here. ... For the science fiction film, see Event Horizon (film). ...

Do black holes have "no hair"?

Main article: No hair theorem

The "No hair" theorem states that black holes have only 3 independent internal properties: mass, angular momentum and electric charge. It is impossible to tell the difference between a black hole formed from a highly compressed mass of normal matter and one formed from, say, a highly compressed mass of anti-matter, in other words, any information about infalling matter or energy is destroyed. This is the black hole information paradox. In astrophysics, the no-hair theorem states that black holes are completely characterized only by three externally observable parameters: mass, electrical charge, and angular momentum. ... In astrophysics, the no-hair theorem states that black holes are completely characterized only by three externally observable parameters: mass, electrical charge, and angular momentum. ... This gyroscope remains upright while spinning due to its angular momentum. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... Antimatter is matter that is composed of the antiparticles of those that constitute normal matter. ... This article or section cites very few or no references or sources. ...

The theorem only works in some of the types of universe which the equations of general relativity allow, but this includes four-dimensional spacetimes with a zero or positive cosmological constant, which describes our universe at the classical level. For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ... In physical cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: Λ) was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe. ... Classical Physics refers to the ideas and laws developed before Relativity and Quantum Theory. ...

Types of black holes

Despite the uncertainty about whether the "No Hair" theorem applies to our universe, astrophysicists currently classify black holes according to their angular momentum (non-zero angular momentum means the black hole is rotating) and electric charge: This gyroscope remains upright while spinning due to its angular momentum. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ...

(All black holes have non-zero mass, so mass cannot be used for this type of "yes" / "no" classification) It has been suggested that Deriving the Schwarzschild solution be merged into this article or section. ... In general relativity, the Kerr metric (or Kerr vacuum) describes the geometry of spacetime around a rotating massive body, such as a rotating black hole. ... In physics and astronomy, a Reissner-Nordström black hole, discovered by Gunnar Nordström and Hans Reissner, is a black hole that carries electric charge , no angular momentum, and mass . ... The Kerr-Newman metric is a solution of Einsteins general relativity field equation that describes the spacetime geometry around a charged (), rotating () black hole of mass m. ...

Physicists do not expect that black holes with a significant electric charge will be formed in nature, because the electromagnetic repulsion which resists the compression of an electrically charged mass is about 40 orders of magnitude greater (about 10⁴⁰ times greater) than the gravitational attraction which compresses the mass. So this article does not cover charged black holes in detail, but the Reissner-Nordström black hole and Kerr-Newman metric articles provide more information. Coulombs torsion balance In physics, Coulombs law is an inverse-square law indicating the magnitude and direction of electrostatic force that one stationary, electrically charged object of small dimensions (ideally, a point source) exerts on another. ... In physics and astronomy, a Reissner-Nordström black hole, discovered by Gunnar Nordström and Hans Reissner, is a black hole that carries mass , electric charge , and no angular momentum. ... The Kerr-Newman metric is a solution of Einsteins general relativity field equation that describes the spacetime geometry around a charged (), rotating () black hole of mass m. ...

On the other hand astrophysicists expect that almost all black holes will rotate, because the stars from which they are formed rotate. In fact most black holes are expected to spin very rapidly, because they retain most of the angular momentum of the stars from which they were formed but concentrated into a much smaller radius. The same laws of angular momentum make skaters spin faster if they pull their arms closer to their bodies. This gyroscope remains upright while spinning due to its angular momentum. ...

This article describes non-rotating, uncharged black holes first, because they are the simplest type.

Major features of non-rotating, uncharged black holes

Event horizon

This is the boundary of the region from which not even light can escape. An observer at a safe distance would see a dull black sphere if the black hole was in a pure vacuum but in front of a light background such as a bright nebula. The event horizon is not a solid surface, and does not obstruct or slow down matter or radiation which is traveling towards the region within the event horizon. Look up Vacuum in Wiktionary, the free dictionary. ... The Triangulum Emission Nebula NGC 604 The Pillars of Creation from the Eagle Nebula For other uses, see Nebula (disambiguation). ... For the science fiction film, see Event Horizon (film). ...

The event horizon is the defining feature of a black hole - it is black because no light or other radiation can escape from inside it. So the event horizon hides whatever happens inside it and we can only calculate what happens by using the best theory available, which at present is general relativity. For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ...

The gravitational field outside the event horizon is identical to the field produced by any other spherically symmetric object of the same mass. The popular conception of black holes as "sucking" things in is false: objects can maintain an orbit around black holes indefinitely provided they stay outside the photon sphere. (described below)

Singularity at a single point

According to general relativity, a black hole's mass is entirely compressed into a region with zero volume, which means its density and gravitational pull are infinite, and so is the curvature of space-time which it causes. These infinite values cause most physical equations, including those of general relativity, to stop working at the center of a black hole. So physicists call the zero-volume, infinitely dense region at the center of a black hole a "singularity". The infinity symbol ∞ in several typefaces. ... A gravitational singularity (sometimes spacetime singularity) is, approximately, a place where quantities which are used to measure the gravitational field become infinite. ...

The singularity in a non-rotating, uncharged black hole is a point, in other words it has zero length, width and height.

But there is an important uncertainty about this description: quantum mechanics is as well-supported by mathematics and experimental evidence as general relativity, and does not allow objects to have zero size - so quantum mechanics says the center of a black hole is not a singularity but just a very large mass compressed into the smallest possible volume. At present we have no well-established theory which combines quantum mechanics and general relativity; and the most promising candidate, string theory, also does not allow objects to have zero size. Fig. ... This article or section is in need of attention from an expert on the subject. ... Interaction in the subatomic world: world lines of pointlike particles in the Standard Model or a world sheet swept up by closed strings in string theory String theory is a model of fundamental physics whose building blocks are one-dimensional extended objects called strings, rather than the zero-dimensional point...

The rest of this article will follow the predictions of general relativity, because quantum mechanics deals with very small-scale (sub-atomic) phenomena and general relativity is the best theory we have at present for explaining large-scale phenomena such as the behavior of masses similar to or larger than stars.

A photon sphere

A non-rotating black hole's photon sphere is a spherical boundary of zero thickness such that photons moving along tangents to the sphere will be trapped in a circular orbit. For non-rotating black holes, the photon sphere has a radius 1.5 times larger than the radius of the event horizon. No photon is likely to stay in this orbit for long, for two reasons. First, it is likely to interact with any infalling matter in the vicinity (being absorbed or scattered). Second, the orbit is dynamically unstable; small deviations from a perfectly circular path will grow into larger deviations very quickly, causing the photon to either escape or fall into the hole. A photon sphere is a spherical region of space surrounding extremely massive objects such as black holes. ... For other uses, see tangent (disambiguation). ... Instability in systems is generally characterized by some of the outputs or internal states growing without bounds. ...

Other extremely compact objects such as neutron stars can also have photon spheres.^[10] This follows from the fact that light "captured" by a photon sphere does not pass within the radius that would form the event horizon if the object were a black hole of the same mass, and therefore its behavior does not depend on the presence of an event horizon. This article is about the celestial body. ... The Schwarzschild radius (sometimes inappropriately referred to as the gravitational radius[1]) is a characteristic radius associated with every mass. ...

Accretion disk

Space is not a pure vacuum - even interstellar space contains a few atoms of hydrogen per cubic centimeter.^[11] The powerful gravity field of a black hole pulls this towards and then into the black hole. The gas nearest the event horizon forms a disk and, at this short range, the black hole's gravity is strong enough to compress the gas to a relatively high density. The pressure, friction and other mechanisms within the disk generate enormous energy - in fact they convert matter to energy more efficiently than the nuclear fusion processes that power stars. As a result, the disk glows very brightly, although disks around black holes radiate mainly X-rays rather than visible light. Look up Vacuum in Wiktionary, the free dictionary. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ...

Accretion disks are not proof of the presence of black holes, because other massive, ultra-dense objects such as neutron stars and white dwarfs cause accretion disks to form and to behave in the same ways as those around black holes. This article is about the celestial body. ... A white dwarf is an astronomical object which is produced when a low to medium mass star dies. ...

Major features of rotating black holes

Main article: Rotating black hole

Two important surfaces around a rotating black hole. The inner sphere is the static limit (the event horizon). It is the inner boundary of a region called the ergosphere. The oval-shaped surface, touching the event horizon at the poles, is the outer boundary of the ergosphere. Within the ergosphere a particle is forced (dragging of space and time) to rotate and may gain energy at the cost of the rotational energy of the black hole (Penrose process).

Rotating black holes share many of the features of non-rotating black holes - inability of light or anything else to escape from within their event horizons, accretion disks, etc. But general relativity predicts that rapid rotation of a large mass produces further distortions of space-time in addition to those which a non-rotating large mass produces, and these additional effects make rotating black holes strikingly different from non-rotating ones. A rotating black hole (Kerr black hole or Kerr-Newman black hole) is a black hole that possesses angular momentum. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... A rotating black hole (Kerr black hole or Kerr-Newman black hole) is a black hole that possesses angular momentum. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... In special relativity and general relativity, time and three-dimensional space are treated together as a single four-dimensional pseudo-Riemannian manifold called spacetime. ...

Two event horizons

If two rotating black holes have the same mass but different rotation speeds, the inner event horizon of the faster-spinning black hole will have a larger radius and its outer event horizon will have a smaller radius than in the slower-spinning black hole. In the most extreme case the two event horizons have zero radius, the region hidden by them has zero size and therefore the object is not a black hole but a naked singularity. Many physicists think that some principle which has not yet been discovered prevents the existence of a naked singularity and therefore prevents a black hole from spinning fast enough to create one. blah blah blah, some people believe God made the universe and that is all there is. ... It has been suggested that Naked singularity be merged into this article or section. ...

Two photon spheres

General relativity predicts that a rotating black hole has two photon spheres, one for each event horizon. A beam of light traveling in a direction opposite to the spin of the black hole will circularly orbit the hole at the outer photon sphere. A beam of light traveling in the same direction as the black hole's spin will circularly orbit at the inner photon sphere. This beam will then split itself in two and both pieces will move into the Hole.

Ergosphere

A large, ultra-dense rotating mass creates an effect called frame-dragging, so that space-time is dragged around it in the direction of the rotation. According to Albert Einsteins theory of general relativity, space and time get pulled out of shape near a rotating body in a phenomenon referred to as frame-dragging. ... In special relativity and general relativity, time and three-dimensional space are treated together as a single four-dimensional pseudo-Riemannian manifold called spacetime. ...

Rotating black holes have an ergosphere, a region bounded by: A rotating black hole (Kerr black hole or Kerr-Newman black hole) is a black hole that possesses angular momentum. ...

• on the outside, an oblate spheroid which coincides with the event horizon at the poles and is noticeably wider around the "equator". This boundary is sometimes called the "ergosurface", but it is just a boundary and has no more solidity than the event horizon. At points exactly on the ergosurface, space-time is dragged around at the speed of light.
• on the inside, the outer event horizon.

Within the ergosphere space-time is dragged around faster than light - general relativity forbids material objects to travel faster than light (so does special relativity), but allows regions of space-time to move faster than light relative to other regions of space-time. An oblate spheroid is ellipsoid having a shorter axis and two equal longer axes. ... For a less technical and generally accessible introduction to the topic, see Introduction to special relativity. ...

Objects and radiation (including light) can stay in orbit within the ergosphere without falling to the center. But they cannot hover (remain stationary as seen by an external observer) because that would require them to move backwards faster than light relative to their own regions of space-time, which are moving faster than light relative to an external observer.

Objects and radiation can also escape from the ergosphere. In fact the Penrose process predicts that objects will sometimes fly out of the ergosphere, obtaining the energy for this by "stealing" some of the black hole's rotational energy. If a large total mass of objects escapes in this way the black hole will spin more slowly and may even stop spinning eventually. To meet Wikipedias quality standards, this article or section may require cleanup. ...

Ring-shaped singularity

General relativity predicts that a rotating black hole will have a ring singularity which lies in the plane of the "equator" and has zero width and thickness - but remember that quantum mechanics does not allow objects to have zero size in any dimension (their wavefunction must spread), so general relativity's prediction is only the best idea we have until someone devises a theory which combines general relativity and quantum mechanics. In general relativity the gravitational singularity at the centre of a rotating black hole (a Kerr black hole) is supposed to form a circle rather than a point. ... Fig. ... This article discusses the concept of a wavefunction as it relates to quantum mechanics. ... This article or section is in need of attention from an expert on the subject. ...

Possibility of escaping from a rotating black hole

Penrose diagrams of various Schwarzschild solutions. Time is the vertical dimension, space is horizontal, and light travels at 45° angles. Paths less than 45° to the horizontal are forbidden by special relativity, but rotating black holes allow for travel to future "universes"

Kerr's solution for the equations of general relativity predicts that: Image File history File links Size of this preview: 685 × 599 pixelsFull resolution (695 × 608 pixel, file size: 31 KB, MIME type: image/png) Penrose Diagrams of various Schwarzschild solutions I, the creator of this work, hereby release it into the public domain. ... Image File history File links Size of this preview: 685 × 599 pixelsFull resolution (695 × 608 pixel, file size: 31 KB, MIME type: image/png) Penrose Diagrams of various Schwarzschild solutions I, the creator of this work, hereby release it into the public domain. ... In theoretical physics, a Penrose diagram (named after Roger Penrose who invented them) is usually a two-dimensional diagram that captures the causal relations between different points in spacetime. ... In general relativity, the Kerr metric (or Kerr vacuum) describes the geometry of spacetime around a rotating massive body, such as a rotating black hole. ...

• The properties of space-time between the two event horizons allow objects to move only towards the singularity.
• But the properties of space-time within the inner event horizon allow objects to move away from the singularity, pass through another set of inner and outer event horizons, and emerge out of the black hole into another universe or another part of this universe without traveling faster than the speed of light.
• Passing through the ring shaped singularity may allow entry to a negative gravity universe.^[12]

If this is true, rotating black holes could theoretically provide the wormholes which often appear in science fiction. Unfortunately, it is unlikely that the internal properties of a rotating black hole are exactly as described by Kerr's solution^[13] and it is not currently known whether the actual properties of a rotating black hole would provide a similar escape route for an object via the inner event horizon. In special relativity and general relativity, time and three-dimensional space are treated together as a single four-dimensional pseudo-Riemannian manifold called spacetime. ... In special relativity and general relativity, time and three-dimensional space are treated together as a single four-dimensional pseudo-Riemannian manifold called spacetime. ... For other uses, see Universe (disambiguation). ... “Lightspeed” redirects here. ... A wormhole, also known as an Einstein-Rosen bridge, is a hypothetical topological feature of spacetime that is essentially a shortcut from one point in the universe to another point in the universe, allowing travel between them that is faster than it would take light to make the journey through... Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ...

Even if this escape route is possible, it is unlikely to be useful because a spacecraft which followed that path would probably be distorted beyond recognition by spaghettification. Click here for animated version Spaghettification is caused by the gravitational forces acting on the four objects. ...

What happens when something falls into a black hole?

This section describes what happens when something falls into a non-rotating, uncharged black hole. The effects of rotating and charged black holes are more complicated but the final result is much the same - the falling object is absorbed (unless rotating black holes really can act as wormholes). A wormhole, also known as an Einstein-Rosen bridge, is a hypothetical topological feature of spacetime that is essentially a shortcut from one point in the universe to another point in the universe, allowing travel between them that is faster than it would take light to make the journey through...

Spaghettification

An object in any very strong gravitational field feels a tidal force stretching it in the direction of the object generating the gravitational field. This is because the inverse square law causes nearer parts of the stretched object to feel a stronger attraction than farther parts. Near black holes, the tidal force is expected to be strong enough to deform any object falling into it; this is called spaghettification. Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... In physics, an inverse-square law is any physical law stating that some quantity is inversely proportional to the square of the distance from a point. ... Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... Click here for animated version Spaghettification is caused by the gravitational forces acting on the four objects. ...

The strength of the tidal force depends on how gravitational attraction changes with distance, rather than on the absolute force being felt. This means that small black holes cause spaghettification while infalling objects are still outside their event horizons, whereas objects falling into large, supermassive black holes may not be deformed or otherwise feel excessively large forces before passing the event horizon. Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... For the science fiction film, see Event Horizon (film). ... Top: artists conception of a supermassive black hole drawing material from a nearby star. ...

Before the falling object crosses the event horizon

An object in a gravitational field experiences a slowing down of time, called gravitational time dilation, relative to observers outside the field. The observer will see that physical processes in the object, including clocks, appear to run slowly. As a test object approaches the event horizon, its gravitational time dilation (as measured by an observer far from the hole) would approach infinity. A pocket watch, a device used to tell time Look up time in Wiktionary, the free dictionary. ... Gravitational time dilation is a consequence of Albert Einsteins theories of relativity and related theories which causes time to pass at different rates in regions of a different gravitational potential; the higher the local distortion of spacetime due to gravity, the slower time passes. ...

From the viewpoint of a distant observer, an object falling into a black hole appears to slow down, approaching but never quite reaching the event horizon: and it appears to become redder and dimmer, because of the extreme gravitational red shift caused by the gravity of the black hole. Eventually, the falling object becomes so dim that it can no longer be seen, at a point just before it reaches the event horizon. All of this is a consequence of time dilation: the object's movement is one of the processes that appear to run slower and slower, and the time dilation effect is more significant than the acceleration due to gravity; the frequency of light from the object appears to decrease, making it look redder, because the light appears to complete fewer cycles per "tick" of the observer's clock; lower-frequency light has less energy and therefore appears dimmer. For other topics related to Einstein see Einstein (disambig) In the general theory of relativity by Albert Einstein, the gravitational redshift or Einstein shift is the effect that clocks in a gravitational field tick slower when observed by a distant observer. ... FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ...

From the viewpoint of the falling object, distant objects may appear either blue-shifted or red-shifted, depending on the falling object's trajectory. Light is blue-shifted by the gravity of the black hole, but is red-shifted by the velocity of the infalling object. Blue shift is the opposite of redshift, the latter being much more noted due to its importance to modern astronomy. ... Redshift of spectral lines in the optical spectrum of a supercluster of distant galaxies (right), as compared with that of the Sun (left). ...

As the object passes through the event horizon

From the viewpoint of the falling object, nothing particularly special happens at the event horizon (apart from spaghettification due to tidal forces, if the black hole has relatively low mass). An infalling object takes a finite proper time to fall past the event horizon. Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... In relativity, proper time is time measured by a single clock between events that occur at the same place as the clock. ...

An outside observer, however, will never see an infalling object cross this surface. The object appears to halt just above the horizon, due to gravitational redshift, fading from view as its light is red-shifted and the rate at which it emits photons drops to approach zero. This doesn't mean that the object never crosses the horizon; instead, it means that light from the horizon-crossing event is delayed by a time that approaches infinity as the object approaches the horizon. The time of crossing depends on how the outside observer chooses to define space and time axes on spacetime near the horizon. This article or section is in need of attention from an expert on the subject. ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... For other uses of this term, see Spacetime (disambiguation). ...

Inside the event horizon

The object reaches the singularity at the center within a finite amount of proper time, as measured by the falling object. An observer on the falling object would continue to see objects outside the event horizon, blue-shifted or red-shifted depending on the falling object's trajectory. Objects closer to the singularity aren't seen, as all paths light could take from objects farther in point inwards towards the singularity. In relativity, proper time is time measured by a single clock between events that occur at the same place as the clock. ... Blue shift is the opposite of redshift, the latter being much more noted due to its importance to modern astronomy. ... Redshift of spectral lines in the optical spectrum of a supercluster of distant galaxies (right), as compared with that of the Sun (left). ...

The amount of proper time a faller experiences below the event horizon depends upon where they started from rest, with the maximum being for someone who starts from rest at the event horizon. A study in 2007 examined the effect of firing a rocket pack with the black hole, showing that this can only reduce the proper time of a person who starts from rest at the event horizon. However, for anyone else, a judicial burst of the rocket can extend the life time of the faller, but over doing it will again reduce the proper time experienced. However, this cannot prevent the inevitable collision with the central singularity.^[14]

Hitting the singularity

As an infalling object approaches the singularity, tidal forces acting on it approach infinity. All components of the object, including atoms and subatomic particles, are torn away from each other before striking the singularity. At the singularity itself, effects are unknown; a theory of quantum gravity is needed to accurately describe events near it. Regardless, as soon as an object passes within the hole's event horizon, it is lost to the outside universe. An observer far from the hole simply sees the hole's mass, charge, and angular momentum change to reflect the addition of the new object's matter. After the event horizon all is unknown. Anything that passes this point cannot be retrieved to study. Many people believe that the matter is extremely compacted. Stephen Hawking made a theory that the matter disappeared into the universe, defying the laws of physics. He later revised this theory to say that the disappearing matter was compensated by parallel universes without black holes, saying, in the end, the matter was not lost. Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... For other uses, see Atom (disambiguation). ... Helium atom (not to scale) Showing two protons (red), two neutrons (green) and a probability cloud (gray) of two electrons (yellow). ... This article does not cite any references or sources. ... ...

Formation and evaporation

Formation of stellar-mass black holes

Stellar-mass black holes are formed in two ways: A stellar black hole is a black hole formed by the gravitational collapse of a massive star (3 or more solar masses) at the end of its lifetime. ...

• As a direct result of the gravitational collapse of a star.
• By collisions between neutron stars.^[15] Although neutron stars are fairly common, collisions appear to be very rare. Neutron stars are also formed by gravitational collapse, which is therefore ultimately responsible for all stellar-mass black holes.

Stars undergo gravitational collapse when they can no longer resist the pressure of their own gravity. This usually occurs either because a star has too little "fuel" left to maintain its temperature, or because a star which would have been stable receives a lot of extra matter in a way which does not raise its core temperature. In either case the star's temperature is no longer high enough to prevent it from collapsing under its own weight (Charles's law explains the connection between temperature and volume). This article or section does not cite its references or sources. ... STARS can mean: Shock Trauma Air Rescue Society Special Tactics And Rescue Service, a fictional task force that appears in Capcoms Resident Evil video game franchise. ... This article or section does not cite its references or sources. ... Cross section of a red giant showing nucleosynthesis and elements formed Stellar nucleosynthesis is the collective term for the nuclear reactions taking place in stars to build the nuclei of the heavier elements. ... Wikibooks has more about this subject: Constructing school science lab equipment/Making Charles law tubes AARON IS SO COOL!!!!! Charles law (sometimes called the Law of Charles) is one of the gas laws. ...

The collapse transforms the matter in the star's core into a denser state which forms one of the types of compact star. Which type of compact star is formed depends on the mass of the remnant, i.e. of the matter left to be compressed after the supernova (if one happened - see below) triggered by the collapse has blown away the outer layers. Degenerate matter is matter which has sufficiently high density that the dominant contribution to its pressure arises from the Pauli exclusion principle. ... In astronomy, the term compact star (sometimes compact object) is used to refer collectively to white dwarfs, neutron stars, other exotic dense stars, and black holes. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ...

Only the largest remnants, those exceeding 1.4 solar masses (known as the Chandrasekhar limit), generate enough pressure to produce black holes, because singularities are the most radically transformed state of matter known to physics (if you can still call it matter) and the force which resists this level of compression, neutron degeneracy pressure, is extremely strong. Remnants exceeding 5 solar masses are produced by stars which were over 20 solar masses before the collapse (the rest of the mass is usually blown into space by the supernova triggered by the collapse). The Chandrasekhar limit, is the maximum mass possible for a white dwarf (one of the end stages of stars when they cool down) and is approximately 3 × 1030 kg, around 1. ... Degenerate matter is matter which has sufficiently high density that the dominant contribution to its pressure arises from the Pauli exclusion principle. ...

In stars which are too large to form white dwarfs, the collapse releases energy which usually produces a supernova, blowing the star's outer layers into space so that they form a spectacular nebula. But the supernova is a side-effect and does not directly contribute to producing a compact star. For example a few gamma ray bursts were expected to be followed by evidence of supernovae but this evidence did not appear,^[16][17] and one explanation is that some very large stars can form black holes fast enough to swallow the whole star before the supernova blast can reach the surface. This article or section does not adequately cite its references or sources. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... The Triangulum Emission Nebula NGC 604 The Pillars of Creation from the Eagle Nebula For other uses, see Nebula (disambiguation). ... In astronomy, gamma-ray bursts (GRBs) are flashes of gamma rays that last from seconds to hours, the longer ones being followed by several days of X-ray afterglow. ...

Formation of larger black holes

There are two main ways in which black holes of larger than stellar mass can be formed:

• Stellar-mass black holes may act as "seeds" which grow by absorbing mass from interstellar gas and dust, stars and planets or smaller black holes.
• Star clusters of large total mass may be merged into single bodies by their members' gravitational attraction. This will usually produce a supergiant or hypergiant star which runs short of "fuel" in a few million years and then undergoes gravitational collapse, produces a supernova or hypernova and spends the rest of its existence as a black hole.

Supergiants are the most massive stars. ... This article does not cite its references or sources. ... Cross section of a red giant showing nucleosynthesis and elements formed Stellar nucleosynthesis is the collective term for the nuclear reactions taking place in stars to build the nuclei of the heavier elements. ... This article needs additional references or sources for verification. ...

Formation of smaller black holes

No known process currently active in the universe can form black holes of less than stellar mass. This is because all present black hole formation is through gravitational collapse, and the smallest mass which can collapse to form a black hole produces a hole approximately 1.5-3.0 times the mass of the sun (the Tolman-Oppenheimer-Volkoff limit). Smaller masses collapse to form white dwarf stars or neutron stars. Sol redirects here. ... This article is in need of attention from an expert on the subject. ... This article or section does not adequately cite its references or sources. ... For the Hugo Award-winning story by Larry Niven, see Neutron Star (story). ...

There are still a few ways in which smaller black holes might be formed, or might have formed in the past:

• By evaporation of larger black holes. If the initial mass of the hole was stellar mass, the time required for it to lose most of its mass via Hawking evaporation is much longer than the age of the universe, so small black holes are not expected to have formed by this method yet.
• By the Big Bang, which produced sufficient pressure to form smaller black holes without the need for anything resembling a star. None of these hypothesized primordial black holes have been detected.
• By very powerful particle accelerators. In principle, a sufficiently energetic collision within a particle accelerator could produce a micro black hole. In practice, this is expected to require energies comparable to the Planck energy, which is vastly beyond the capability of any present, planned, or expected future particle accelerator to produce. Some variant models of the unification of the four fundamental forces allow the formation of black holes at much lower energies. This would allow production of extremely short-lived black holes in terrestrial particle accelerators. No conclusive evidence of this type of black hole production has been presented as of 2007.

In physics, Hawking radiation is thermal radiation emitted by black holes due to quantum effects. ... The age of the universe, in Big Bang cosmology, refers to the time elapsed between the Big Bang and the present day. ... For other uses, see Big Bang (disambiguation). ...