Black holes

A black hole is an astronomical body so compact that its gravity prevents anything, including light, from escaping. Albert Einstein's theory of general relativity, which describes gravitation as the curvature of spacetime, predicts that any sufficiently compact mass will form a black hole. The boundary of no escape is called the event horizon. In general relativity, crossing a black hole's event horizon traps an object inside but produces no locally detectable change. General relativity also predicts that every black hole should have a central singularity, where the curvature of spacetime is infinite.

propagating spacetime ripple

thumb|upright=1.3|A wormhole visualized as a two-dimensional surface. Route (a) is the shortest path through normal space between points 1 and 2; route (b) is a shorter path through a wormhole.

boundary of a region of spacetime from which one cannot escape once entered

black hole with mass above 10⁵ solar masses, usually found at the centers of galaxies

radiation with a blackbody spectrum radiated from an event horizon

structure formed by diffuse material in orbital motion around a massive central body

distance from a massive body where the escape velocity equals the speed of light

contraction of an astronomical object due to the influence of its own gravity

black hole formed by a collapsed star

spherically symmetric static vacuum solution of Einstein’s field equations with zero cosmological constant

beam of ionized matter flowing along the axis of a rotating astronomical object

physical principle in which physics inside a bounded region is fully captured by physics at the boundary of the region

a hypothetical gravitational singularity without an event horizon

black hole on a quantum level or with quantum effects

alt=|thumb|Astronaut falling into a black hole (schematic illustration of the spaghettification effect) thumb|upright=1.3|Tidal forces acting on a spherical body in a non-homogeneous [[gravitational field. In this diagram, the gravitational force originates from a source to the right. It shows both the tidal field (thick red arrows) and the gravity field (thin blue arrows) exerted on the body's surface and center (label O) by a source (label S).]]

scientific question of whether information can disappear in a black hole

hypothetical type of black hole that formed soon after the Big Bang

upper bound to the mass of cold, nonrotating neutron stars

thumb|alt=|upright=1.3|An artist’s impression of a quasi-star, showing a black hole core residing in the massive photospheric envelope of the object

thumb|right|300px|At the ergospheres (shown here in violet for the outer and red for the inner one), the temporal metric coefficient gtt becomes negative, i.e., acts like a purely spatial metric component. Consequently, timelike or lightlike worldlines within this region must co-rotate with the inner mass. Kerr–Newman metric#Alternative .28Kerr.E2.80.93Schild.29 formulation|Cartesian projection, equatorial perspective.

exact solution for the Einstein field equations

standard surface gravity

area of physical study that seeks to reconcile the laws of thermodynamics with the existence of black hole event horizons

black hole with a mass range of 100 to 100000 solar masses

hypothetical object whose Schwarzschild radius is approximately the same as its Compton wavelength

hypothetical astronomical object heated by dark-matter annihilation

spherically symmetric metric with electric charge

black hole with angular momentum

thumb|A diagram comparing the structure of a classical black hole with a gravastar.

theorical process wherein energy can be extracted from a rotating black hole

theorem

system consisting of two black holes orbiting each other

conjecture that, in general relativity, there is no naked singularity (i.e. one visible from future null infinity) generically

process that leads to gradual decrease of the distance between two orbiting bodies

Upper limit on entropy that can be contained within a given finite region of space which has a finite amount of energy, in physics.

thumb |Artist's impression of the view of the sky from a planet orbiting inside the dust disk around the supermassive black hole in the center of the galaxy NGC 4261.

Turkish-American astronomer (born 1975)

spherical area or region of space where gravity is strong enough that massless particles are forced to travel in orbits

theorized concentration of light so intense that it forms an event horizon and becomes self-trapped

nonsingular electromagnetic or gravitational wave held together in a confined region by the gravitational attraction of its own field energy

pulling apart of a star by tidal forces when it gets too close to a supermassive black hole

brightest galaxy within a galaxy cluster

light-like boundary of the domain of validity of a Cauchy problem in general relativity

gravitational object composed of matter

cosmological model in which the observable universe is the interior of a black hole

black hole with maximal charge or angular momentum allowed for a given mass

black holes appearing from quantum spacetime fluctuations

general relativity model near the beginning of the universe

hypothetical phenomenon where an observer falling into a black hole encounters high-energy quanta at the event horizon

hypothetical astronomical object, theorized as a compact, exotic star, that exists within a black hole's event horizon, created when the energy density of a collapsing star reaches the Planck energy density

class of small, red galaxies

object composed of dark energy that outwardly resembles a black hole

Ring-shaped gravitational singularity of a rotating blackhole

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conjencture unifying entanglement and wormholes

compact object with an intrinsic magnetic field that collapses continuously without forming an event horizon

In astronomy, blitzars are a hypothetical type of neutron star, specifically pulsars that can rapidly collapse into black holes if their spinning slows down. Heino Falcke and Luciano Rezzolla proposed these stars in 2013 as an explanation for fast radio bursts.

acoustic analogue of a black hole where phonons cannot escape an analogue event horizon