outline
Outline or outlining may refer to:
* Outline (list), a document summary, in hierarchical list format
* Code folding, a method of hiding or collapsing code or text to see content in outline form
* Outline drawing, a sketch depicting the outer edge ...
is provided as an overview of and topical guide to black holes:
Black hole
A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...
– mathematically defined region of
spacetime
In physics, spacetime is a mathematical model that combines the three dimensions of space and one dimension of time into a single four-dimensional manifold. Spacetime diagrams can be used to visualize relativistic effects, such as why differen ...
exhibiting such a strong gravitational pull that no particle or electromagnetic radiation can escape from inside it. The theory of
general relativity
General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...
predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of the region from which no escape is possible is called the event horizon. Although crossing the event horizon has enormous effect on the fate of the object crossing it, it appears to have no locally detectable features. In many ways a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is on the order of billionths of a kelvin for black holes of stellar mass, making it essentially impossible to observe.
What ''type'' of thing is a black hole?
A black hole can be described as all of the following:
*
Astronomical object
An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often us ...
Schwarzschild metric
In Einstein's theory of general relativity, the Schwarzschild metric (also known as the Schwarzschild solution) is an
exact solution to the Einstein field equations that describes the gravitational field outside a spherical mass, on the assumpti ...
– In Einstein's theory of general relativity, the Schwarzschild solution, named after Karl Schwarzschild, describes the gravitational field outside a spherical, uncharged, non-rotating mass such as a star, planet, or black hole.
*
Rotating black hole
A rotating black hole is a black hole that possesses angular momentum. In particular, it rotates about one of its axes of symmetry.
All celestial objects – planets, stars (Sun), galaxies, black holes – spin.
Types of black holes
There a ...
– black hole that possesses spin angular momentum.
*
Charged black hole
A charged black hole is a black hole that possesses electric charge. Since the electromagnetic repulsion in compressing an electrically charged mass is dramatically greater than the gravitational attraction (by about 40 orders of magnitude), it is ...
– black hole that possesses electric charge.
* Virtual black hole – black hole that exists temporarily as a result of a quantum fluctuation of spacetime.
Types of black holes, by size
*
Micro black hole
Micro black holes, also called mini black holes or quantum mechanical black holes, are hypothetical tiny (<1 )
– predicted as tiny black holes, also called quantum mechanical black holes, or mini black holes, for which quantum mechanical effects play an important role. These could potentially have arisen as
primordial black hole
Primordial black holes (also abbreviated as PBH) are hypothetical black holes that formed soon after the Big Bang. Due to the extreme environment of the newly born universe, extremely dense pockets of sub-atomic matter had been tightly packed to ...
s.
*
Extremal black hole
In theoretical physics, an extremal black hole is a black hole with the minimum possible mass that is compatible with its electric charge, charge and angular momentum.
The concept of an extremal black hole is theoretical and none have thusfar bee ...
– black hole with the minimal possible mass that can be compatible with a given charge and angular momentum.
** Black hole electron – if there were a black hole with the same mass and charge as an electron, it would share many of the properties of the electron including the magnetic moment and Compton wavelength.
*
Stellar black hole
A stellar black hole (or stellar-mass black hole) is a black hole formed by the gravitational collapse of a star. They have masses ranging from about 5 to several tens of solar masses. The process is observed as a hypernova explosion or as a gam ...
– black hole formed by the gravitational collapse of a massive star. They have masses ranging from about three to several tens of solar masses.
* Intermediate-mass black hole – black hole whose mass is significantly more than stellar black holes yet far less than supermassive black holes.
* Supermassive black hole – largest type of black hole in a galaxy, on the order of hundreds of thousands to billions of solar masses.
*
Quasar
A quasar is an extremely Luminosity, luminous active galactic nucleus (AGN). It is pronounced , and sometimes known as a quasi-stellar object, abbreviated QSO. This emission from a galaxy nucleus is powered by a supermassive black hole with a m ...
– very energetic and distant active galactic nucleus.
** Active galactic nucleus – compact region at the centre of a galaxy that has a much higher than normal luminosity over at least some portion, and possibly all, of the electromagnetic spectrum.
**
Blazar
A blazar is an active galactic nucleus (AGN) with a relativistic jet (a jet composed of ionized matter traveling at nearly the speed of light) directed very nearly towards an observer. Relativistic beaming of electromagnetic radiation from the ...
– very compact quasar associated with a presumed supermassive black hole at the center of an active, giant elliptical galaxy.
Specific black holes
*
List of black holes
This list of black holes (and stars considered probable candidates) is organized by mass (including black holes of undetermined mass); some items in this list are galaxies or star clusters that are believed to be organized around a black hole. M ...
– incomplete list of black holes organized by size; some items in this list are galaxies or star clusters that are believed to be organized around a black hole.
Black hole exploration
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Rossi X-ray Timing Explorer
The Rossi X-ray Timing Explorer (RXTE) was a NASA satellite that observed the time variation of astronomical X-ray sources, named after physicist Bruno Rossi. The RXTE had three instruments — an All Sky Monitor, the High-Energy X-ray Timing ...
– satellite that observes the time structure of astronomical X-ray sources, named after Bruno Rossi.
Formation of black holes
*
Stellar evolution
Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is cons ...
– process by which a star undergoes a sequence of radical changes during its lifetime.
*
Gravitational collapse
Gravitational collapse is the contraction of an astronomical object due to the influence of its own gravity, which tends to draw matter inward toward the center of gravity. Gravitational collapse is a fundamental mechanism for structure formatio ...
– inward fall of a body due to the influence of its own gravity.
*
Neutron star
A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...
– type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event.
* Compact star – white dwarfs, neutron stars, other exotic dense stars, and black holes.
** Quark star – hypothetical type of exotic star composed of quark matter, or strange matter.
**
Exotic star
An exotic star is a hypothetical compact star composed of exotic matter (something not made of electrons, protons, neutrons or muons), and balanced against gravitational collapse by degeneracy pressure or other quantum properties. Exotic stars incl ...
– compact star composed of something other than electrons, protons, and neutrons balanced against gravitational collapse by degeneracy pressure or other quantum properties.
*
Tolman–Oppenheimer–Volkoff limit The Tolman–Oppenheimer–Volkoff limit (or TOV limit) is an upper bound to the mass of cold, nonrotating neutron stars, analogous to the Chandrasekhar limit for white dwarf stars. If the mass of the said star reaches the limit it will collapse to ...
– upper bound to the mass of stars composed of neutron-degenerate matter.
*
White dwarf
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes fro ...
– also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter.
*
Supernova
A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...
– stellar explosion that is more energetic than a nova.
* Hypernova – also known as a Type Ic Supernova, refers to an immensely large star that collapses at the end of its lifespan.
* Gamma-ray burst – flashes of gamma rays associated with extremely energetic explosions that have been observed in distant galaxies.
Properties of black holes
*
Accretion disk
An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is typically a star. Friction, uneven irradiance, magnetohydrodynamic effects, and other fo ...
– structure (often a circumstellar disk) formed by diffused material in orbital motion around a massive central body, typically a star. Accretion disks of black holes radiate in the X-ray part of the spectrum.
* Black hole thermodynamics – area of study that seeks to reconcile the laws of thermodynamics with the existence of black hole event horizons.
*
Schwarzschild radius
The Schwarzschild radius or the gravitational radius is a physical parameter in the Schwarzschild solution to Einstein's field equations that corresponds to the radius defining the event horizon of a Schwarzschild black hole. It is a characteristic ...
– distance from the center of an object such that, if all the mass of the object were compressed within that sphere, the escape speed from the surface would equal the speed of light.
*
M–sigma relation
The M–sigma (or ''M''–''σ'') relation is an empirical correlation between the stellar velocity dispersion ''σ'' of a galaxy bulge and the mass M of the supermassive black hole at its center.
The ''M''–''σ'' relation was first presented i ...
– empirical correlation between the stellar velocity dispersion of a galaxy bulge and the mass M of the supermassive black hole at
* Event horizon – boundary in spacetime beyond which events cannot affect an outside observer.
* Quasi-periodic oscillation – manner in which the X-ray light from an astronomical object flickers about certain frequencies.
*
Photon sphere
A photon sphere or photon circle is an area or region of space where gravity is so strong that photons are forced to travel in orbits, which is also sometimes called the last photon orbit. The radius of the photon sphere, which is also the lower ...
– spherical region of space where gravity is strong enough that photons are forced to travel in orbits.
*
Ergosphere
file:Ergosphere_and_event_horizon_of_a_rotating_black_hole_(no_animation).gif, 300px, In the ergosphere (shown here in light gray), the component ''gtt'' is negative, i.e., acts like a purely spatial metric component. Consequently, timelike or ligh ...
– region located outside a rotating black hole.
* Hawking radiation – black-body radiation that is predicted to be emitted by black holes, due to quantum effects near the event horizon.
*
Penrose process
The Penrose process (also called Penrose mechanism) is theorised by Sir Roger Penrose as a means whereby energy can be extracted from a rotating black hole. The process takes advantage of the ergosphere --- a region of spacetime around the black ho ...
– process theorised by Roger Penrose wherein energy can be extracted from a rotating black hole.
* Bondi accretion – spherical accretion onto an object.
*
Spaghettification
In astrophysics, spaghettification (sometimes referred to as the noodle effect) is the vertical stretching and horizontal compression of objects into long thin shapes (rather like spaghetti) in a very strong, non-homogeneous gravitational field ...
– vertical stretching and horizontal compression of objects into long thin shapes in a very strong gravitational field, and is caused by extreme tidal forces.
* Gravitational lens – distribution of matter between a distant source and an observer, that is capable of bending the light from the source, as it travels towards the observer.
Timeline of black hole physics
Timeline of black hole physics
Pre-20th century
* 1640 — Ismaël Bullialdus suggests an inverse-square gravitational force law
* 1676 — Ole Rømer demonstrates that light has a finite speed
* 1684 — Isaac Newton writes do ...
– Timeline of black hole physics
*
John Michell
John Michell (; 25 December 1724 – 21 April 1793) was an English people, English natural philosophy, natural philosopher and clergyman who provided pioneering insights into a wide range of scientific fields including astronomy, geology, opti ...
– geologist who first proposed the idea "dark stars" in 1783
** Dark star
*
Pierre-Simon Laplace
Pierre-Simon, marquis de Laplace (; ; 23 March 1749 – 5 March 1827) was a French scholar and polymath whose work was important to the development of engineering, mathematics, statistics, physics, astronomy, and philosophy. He summarized ...
– early mathematical theorist (1796) of the idea of black holes
*
Albert Einstein
Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...
– in 1915, arrived at the theory of general relativity
*
Karl Schwarzschild
Karl Schwarzschild (; 9 October 1873 – 11 May 1916) was a German physicist and astronomer.
Schwarzschild provided the first exact solution to the Einstein field equations of general relativity, for the limited case of a single spherical non-r ...
– described the gravitational field of a point mass in 1915
*
Subrahmanyan Chandrasekhar
Subrahmanyan Chandrasekhar (; ) (19 October 1910 – 21 August 1995) was an Indian-American theoretical physicist who spent his professional life in the United States. He shared the 1983 Nobel Prize for Physics with William A. Fowler for "... ...
– in 1931, using special relativity, postulated that a non-rotating body of electron-degenerate matter above a certain limiting mass (now called the Chandrasekhar limit at 1.4 solar masses) has no stable solutions.
* David Finkelstein – identified the Schwarzschild surface as an event horizon
* Roy Kerr – In 1963, found the exact solution for a rotating black hole
Models of black holes
* Gravitational singularity – or spacetime singularity is a location where the quantities that are used to measure the gravitational field become infinite in a way that does not depend on the coordinate system.
**
Penrose–Hawking singularity theorems
The Penrose–Hawking singularity theorems (after Roger Penrose and Stephen Hawking) are a set of results in general relativity that attempt to answer the question of when gravitation produces singularities. The Penrose singularity theorem is ...
– set of results in general relativity which attempt to answer the question of when gravitation produces singularities.
*
Primordial black hole
Primordial black holes (also abbreviated as PBH) are hypothetical black holes that formed soon after the Big Bang. Due to the extreme environment of the newly born universe, extremely dense pockets of sub-atomic matter had been tightly packed to ...
– hypothetical type of black hole that is formed not by the gravitational collapse of a large star but by the extreme density of matter present during the universe's early expansion.
* Gravastar – object hypothesized in astrophysics as an alternative to the black hole theory by Pawel Mazur and Emil Mottola.
* Dark star (Newtonian mechanics) – theoretical object compatible with Newtonian mechanics that, due to its large mass, has a surface escape velocity that equals or exceeds the speed of light.
*
Dark-energy star
A dark-energy star is a hypothetical compact astrophysical object, which a minority of physicists think might constitute an alternative explanation for observations of astronomical black hole candidates.
The concept was proposed by physicist G ...
*
Black star (semiclassical gravity)
A black star is a gravitational object composed of matter. It is a theoretical alternative to the black hole concept from general relativity. The theoretical construct was created through the use of semiclassical gravity theory. A similar stru ...
– gravitational object composed of matter.
*
Magnetospheric eternally collapsing object
The magnetospheric eternally collapsing object (MECO) is an alternative model for black holes initially proposed by Indian scientist Abhas Mitra in 1998 and later generalized by American researchers Darryl J. Leiter and Stanley L. Robertson. A pro ...
– proposed alternatives to black holes advocated by Darryl Leiter and Stanley Robertson.
*
Fuzzball (string theory)
Fuzzballs are theorized by some superstring theory scientists to be the true quantum description of black holes. The theory attempts to resolve two intractable problems that classic black holes pose for modern physics:
# The information par ...
– theorized by some superstring theory scientists to be the true quantum description of black holes.
*
White hole
In general relativity, a white hole is a hypothetical region of spacetime and singularity that cannot be entered from the outside, although energy-matter, light and information can escape from it. In this sense, it is the reverse of a black ho ...
– hypothetical region of spacetime which cannot be entered from the outside, but from which matter and light have the ability to escape.
*
Naked singularity
In general relativity, a naked singularity is a hypothetical gravitational singularity without an event horizon. In a black hole, the singularity is completely enclosed by a boundary known as the event horizon, inside which the curvature of spacet ...
– gravitational singularity without an event horizon.
* Ring singularity – describes the altering gravitational singularity of a rotating black hole, or a Kerr black hole, so that the gravitational singularity becomes shaped like a ring.
* Immirzi parameter – numerical coefficient appearing in loop quantum gravity, a nonperturbative theory of quantum gravity.
*
Membrane paradigm
In black hole theory, the black hole membrane paradigm is a simplified model, useful for visualising and calculating the effects predicted by quantum mechanics for the exterior physics of black holes, without using quantum-mechanical principles or ...
– useful "toy model" method or "engineering approach" for visualising and calculating the effects predicted by quantum mechanics for the exterior physics of black holes, without using quantum-mechanical principles or calculations.
*
Kugelblitz (astrophysics)
A kugelblitz is a theoretical astrophysical object predicted by general relativity. It is a concentration of heat, light or radiation so intense that its energy forms an event horizon and becomes self-trapped. In other words, if enough radiation ...
– concentration of light so intense that it forms an event horizon and becomes self-trapped: according to general relativity, if enough radiation is aimed into a region, the concentration of energy can warp spacetime enough for the region to become a black hole.
*
Wormhole
A wormhole (Einstein-Rosen bridge) is a hypothetical structure connecting disparate points in spacetime, and is based on a special Solutions of the Einstein field equations, solution of the Einstein field equations.
A wormhole can be visualize ...
– hypothetical topological feature of spacetime that would be, fundamentally, a "shortcut" through spacetime.
*
Quasi-star
A quasi-star (also called black hole star) is a hypothetical type of extremely massive and luminous star that may have existed early in the history of the Universe. Unlike modern stars, which are powered by nuclear fusion in their cores, a ...
– hypothetical type of extremely massive star that may have existed very early in the history of the Universe.
* Black hole neural network
Issues pertaining to black holes
* No-hair theorem – postulates that all black hole solutions of the Einstein-Maxwell equations of gravitation and electromagnetism in general relativity can be completely characterized by only three ''externally'' observable classical parameters: mass, electric charge, and angular momentum.
* Black hole information paradox – results from the combination of quantum mechanics and general relativity.
*
Cosmic censorship hypothesis The weak and the strong cosmic censorship hypotheses are two mathematical conjectures about the structure of gravitational singularities arising in general relativity.
Singularities that arise in the solutions of Einstein's equations are typically ...
– two mathematical conjectures about the structure of singularities arising in general relativity.
*
Nonsingular black hole models A nonsingular black hole model is a mathematical theory of black holes that avoids certain theoretical problems with the standard black hole model, including information loss and the unobservable nature of the black hole event horizon.
Avoiding ...
– mathematical theory of black holes that avoids certain theoretical problems with the standard black hole model, including information loss and the unobservable nature of the black hole event horizon.
*
Holographic principle
The holographic principle is an axiom in string theories and a supposed property of quantum gravity that states that the description of a volume of space can be thought of as encoded on a lower-dimensional boundary to the region — such as a ...
– property of quantum gravity and string theories which states that the description of a volume of space can be thought of as encoded on a boundary to the region—preferably a light-like boundary like a gravitational horizon.
*
Black hole complementarity
Black hole complementarity is a conjectured solution to the black hole information paradox, proposed by Leonard Susskind, Larus Thorlacius, and Gerard 't Hooft.
Overview
Ever since Stephen Hawking suggested information is lost in an evaporating ...
– conjectured solution to the black hole information paradox, proposed by Leonard Susskind and Gerard 't Hooft.
Black hole metrics
*
Schwarzschild metric
In Einstein's theory of general relativity, the Schwarzschild metric (also known as the Schwarzschild solution) is an
exact solution to the Einstein field equations that describes the gravitational field outside a spherical mass, on the assumpti ...
– describes the gravitational field outside a spherical, uncharged, non-rotating mass such as a star, planet, or black hole.
* Kerr metric – describes the geometry of empty spacetime around an uncharged, rotating black hole (axially symmetric with an event horizon which is topologically a sphere)
*
Reissner–Nordström metric
In physics and astronomy, the Reissner–Nordström metric is a static solution to the Einstein–Maxwell field equations, which corresponds to the gravitational field of a charged, non-rotating, spherically symmetric body of mass ''M''. T ...
– static solution to the Einstein-Maxwell field equations, which corresponds to the gravitational field of a charged, non-rotating, spherically symmetric body of mass ''M''.
* Kerr-Newman metric – solution of the Einstein–Maxwell equations in general relativity, describing the spacetime geometry in the region surrounding a charged, rotating mass.
Astronomical objects including a black hole
*
Hypercompact stellar system A hypercompact stellar system (HCSS) is a dense cluster of stars around a supermassive black hole that has been ejected from the center of its host galaxy. Stars that are close to the black hole at the time of the ejection will remain bound to the ...
– dense cluster of stars around a supermassive black hole that has been ejected from the centre of its host galaxy.
Stanford Encyclopedia of Philosophy
The ''Stanford Encyclopedia of Philosophy'' (''SEP'') combines an online encyclopedia of philosophy with peer-reviewed publication of original papers in philosophy, freely accessible to Internet users. It is maintained by Stanford University. Eac ...
Black hole
A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...
Black hole
A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...