An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A → binary system consisting of two → black holes in close orbit around each other. Same as → black hole binary.

→ binary; → black; → hole.

A → dual supermassive black hole whose components are separated by a few parsecs.

→ binary; → supermassive; → black; → hole.

A fantastically → compact object, predicted by the theory of → general relativity, whose → gravity is so powerful that not even light can escape from it. A black hole forms when matter → collapses to → infinite  → density, producing a → singularity of infinite → curvature in the fabric of → space-time. Each black hole is surrounded by an → event horizon, at which the → escape velocity is the → speed of light. The → Schwarzschild radius for the Sun is about 3 km and for the Earth about 1 cm. There is observational evidence for black holes on a remarkable range of scales in the Universe: → stellar black hole, → intermediate-mass black hole, → primordial black hole, → mini black hole, → supermassive black hole, → Schwarzschild black hole, → Kerr black hole.

Historically, the Newtonian concept of such a celestial body appeared at the end of the 18th century when light was shown to have particle characteristics. In fact the English geologist John Mitchell (1724-1793) and French mathematician and astronomer Pierre Simon Laplace (1749-1827), independently, suggested that regions of space, where gravitational attraction was so strong that not even light could escape, may exist in the Universe. However, the term black hole was coined in 1967 by the Princeton physicist John A. Wheeler (1911-2008); → black; → hole.

A → binary system in which each component is a → black hole. The binary's evolution can be divided into three stages: → inspiral, → merger, and → ringdown.

→ black; → hole; → binary.

An object that seems likely to be a → black hole, but waits for more observational confirmations.

→ black; → hole; → candidate.

A spherical volume of hot plasma over a broader → accretion disk around a → black hole. The observation of energetic X-ray emission from black holes, which is inconsistent with → thermal emission from an accretion disk, is attributed to the presence of a putative hot corona. It has been widely postulated that the → hard X-rays are the product of → inverse Compton scattering of seed photons from accretion disks by hot ccoronae (See, e.g., F.L. Vieyro et al., 2010, arXiv:1005.5398 and R. C. Reis & J. M. Miller, 2013, arXiv:1304.4947).

→ black; → hole; → corona.

The collision of two → black holes in a → binary black hole system once they come so close that they cannot escape each other's gravity. They will merge in an extremely violent event to become one more massive black hole. The merger would produce tremendous energy and send massive ripples, called → gravitational waves, through the → space-time fabric of the Universe. Such an event (called GW150914) was first detected by the → Laser Interferometer Gravitational-Wave Observatory (LIGO) on September 14, 2015. The initial black hole masses were 36 and 29 Msun which gave a final black hole mass of 62 Msun, with 3 Msun radiated in gravitational waves. The event happened at a distance of 1.3 billion → light-years from Earth (Abbott et al., 2016, Phys. Rev. Lett. 116, 061102). Black hole merger is preceded by → inspiral and followed by → ringdown.

→ black; → hole; → merger.

The acceleration of gravity at the → event horizon of a → black hole. For a → Schwarzschild back hole it is given by κ = GM/R_Sch² = c⁴/(4GM).

→ black; → hole; → surface; → gravity.

A gravitationally lensed image of a → black hole as seen by a distant observer if the black hole is in front of a bright background. According to → general relativity, photons circling the black hole slightly inside the boundary of the → photon sphere will fall down into the → event horizon, while photons circling just outside will escape to infinity. The shadow appears therefore as a rather sharp boundary between bright and dark regions and arises from a deficit of those photons that are captured by the event horizon. Because of this, the diameter of the shadow does not depend on the photons energy, but uniquely on the → angular momentum of the black hole. In a pioneering study, Bardeen (1973) calculated the shape of a dark area of a → Kerr black hole, that is, its "shadow" over a bright background appearing, for instance, in the image of a bright star behind the black hole.

→ black; → hole; → shadow.

The outcome of a → merger process between two galaxies, each with its own central → supermassive black hole (SMBH), resulting in a remnant galaxy hosting two SMBHs. Simulations of → galaxy mergers show there should be lots of dual → active galactic nuclei (AGN) visible at less than 10 kpc separations. As of 2015 more than 100 known dual supermassive black holes have been found. See also → binary supermassive black hole.

→ dual; → supermassive; → black; → hole.

A → black hole with a mass in the range 10²-10⁴ solar masses. IMBHs may form as the result of multiple → mergers of smaller objects in the centers of dense stellar clusters in the present universe, assuming → mass loss from → stellar winds is not significant. They may also arise from the evolution of → very massive stars early in the history of the Universe, forming black hole "seeds" in the centers of massive halos (the precursors of the galaxies we see today) early in the history of the Universe, to redshifts z > 10. Currently the best observational evidence for IMBHs comes from models of ultraluminous X-ray sources (See, e.g., J. M. Centrella et al. 2010, astro-ph/1010.5260).

→ intermediate; → mass; → black; → hole.

A → black hole that possesses only mass (not electric charge) and rotates about a central axis. It has an → ergosphere and a → stationary limit.

Named after the New Zealand mathematician Roy P. Kerr (1934-) who, in 1963, was the first to solve the → field equationss of Einstein's theory of → general relativity for a situation of this kind; → black hole.

A rotating charged black hole. Compare with the → Kerr black hole and the → Reissner-Nordstrom black hole.

Named after Roy P. Kerr and Ezra T. Newman (1929-) who in 1963 independently found this solution to Einstein's → field equations; → black; → hole.

A black hole with a mass between millions and billions of solar masses residing in galactic nuclei. The mass of this type of black holes represents about 0.2% of the bulge mass. When matter is swallowed by the black hole, this gives rise to the tremendous energetic phenomena observed in quasars and active galactic nuclei.

→ massive; → black hole.

A black hole of mass as low as 10^-6 gram supposed to have formed in the early Universe following the Big Bang event. Same as primordial black hole.

Mini a shortening of → minimum; → black hole.

A black hole formed following the Big Bang event due to incredibly violent turbulence that squeezed concentrations of matter to high densities. These black holes, first suggested by Stephen Hawking, are expected to have a mass comparable to that of a mountain and a size as small as an atom. Same as → mini black hole.

→ primordial; → black hole.

A type of electrically charged → black hole that is spherically symmetric and non-rotating. Another type of such objects is the → Kerr-Newman black hole.

Named after the German physicist Hans Jacob Reissner (1874-1967) in 1916 and the Finnish Gunnar Nordstrom (1881-1923) in 1918 independently worked out solutions different from those of Schwarzschild; → black hole.

A black hole that possesses angular momentum, as first postulated by Roy C. Kerr in 1963. Opposite of a stationary black hole. → ergosphere.

→ rotating; → black hole.

A → black hole with zero → angular momentum (non-rotating) and zero electric charge derived from Karl Schwarzschild 1916 exact solution to Einstein's vacuum → field equations.

Karl Schwarzschild (1873-1916), German mathematical physicist, who carried out the first relativistic study of black holes. → black hole.

A → black hole with zero → angular momentum, that does not rotate.

→ stationary; → black hole.