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A quasar is an extremely luminous active galactic nucleus (AGN). It is pronounced KWAY-zar, 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 mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous accretion disc. Gas in the disc falling towards the black hole heats up because of friction and releases energy in the form of electromagnetic radiation. The radiant energy of quasars is enormous; the most powerful quasars have luminosities thousands of times greater than that of a galaxy such as the Milky Way. Usually, quasars are categorized as a subclass of the more general category of AGN. The redshifts of quasars are of cosmological origin.
A supermassive black hole is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions of times the mass of the Sun (M☉). Black holes are a class of astronomical objects that have undergone gravitational collapse, leaving behind spheroidal regions of space from which nothing can escape, not even light. Observational evidence indicates that almost every large galaxy has a supermassive black hole at its center. For example, the Milky Way has a supermassive black hole in its Galactic Center, corresponding to the radio source Sagittarius A*. Accretion of interstellar gas onto supermassive black holes is the process responsible for powering active galactic nuclei (AGNs) and quasars.
A blazar is an active galactic nucleus (AGN) with a relativistic jet directed very nearly towards an observer. Relativistic beaming of electromagnetic radiation from the jet makes blazars appear much brighter than they would be if the jet were pointed in a direction away from Earth. Blazars are powerful sources of emission across the electromagnetic spectrum and are observed to be sources of high-energy gamma ray photons. Blazars are highly variable sources, often undergoing rapid and dramatic fluctuations in brightness on short timescales. Some blazar jets exhibit apparent superluminal motion, another consequence of material in the jet traveling toward the observer at nearly the speed of light.
Cepheus is a constellation in the far northern sky, named after Cepheus, a king of Aethiopia in Greek mythology. It is one of the 48 constellations listed by the second century astronomer Ptolemy, and it remains one of the 88 constellations in the modern times.
Sagittarius A*, abbreviated Sgr A*, is the supermassive black hole at the Galactic Center of the Milky Way. It is located near the border of the constellations Sagittarius and Scorpius, about 5.6° south of the ecliptic, visually close to the Butterfly Cluster (M6) and Lambda Scorpii.
4C +37.11 or Galaxy 0402+379 is a radio galaxy and elliptical galaxy featuring binary supermassive black holes with the least separation of any directly observed binaries, as of 2006. The separation between the two is 24 light-years or 7.3 parsecs, with an orbital period of 30,000 years. The two supermassive black holes, about 750 million light years from earth, have a combined mass of about 15 billion M☉.
OJ 287 is a BL Lac object 3.5 billion light-years from Earth that has produced quasi-periodic optical outbursts going back approximately 120 years, as first apparent on photographic plates from 1891. Seen on photographic plates since at least 1887, it was first detected at radio wavelengths during the course of the Ohio Sky Survey. It is a supermassive black hole binary. The intrinsic brightness of the flashes corresponds to over a trillion times the Sun's luminosity, greater than the entire Milky Way galaxy's light output.
Gravitational waves are waves of the intensity of gravity generated by the accelerated masses of an orbital binary system that propagate as waves outward from their source at the speed of light. They were first proposed by Oliver Heaviside in 1893 and then later by Henri Poincaré in 1905 as waves similar to electromagnetic waves but the gravitational equivalent. Gravitational waves were later predicted in 1916 by Albert Einstein on the basis of his general theory of relativity as ripples in spacetime. Later he refused to accept gravitational waves. Gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation. Newton's law of universal gravitation, part of classical mechanics, does not provide for their existence, since that law is predicated on the assumption that physical interactions propagate instantaneously – showing one of the ways the methods of Newtonian physics are unable to explain phenomena associated with relativity.
NGC 4151 is an intermediate spiral Seyfert galaxy with weak inner ring structure located 15.8 megaparsecs from Earth in the constellation Canes Venatici. The galaxy was first mentioned by William Herschel on March 17, 1787; it was one of the six Seyfert galaxies described in the paper which defined the term. It is one of the nearest galaxies to Earth to contain an actively growing supermassive black hole. The black hole would have a mass on the order of 2.5 million to 30 million solar masses. It was speculated that the nucleus may host a binary black hole, with about 40 million and about 10 million solar masses respectively, orbiting with a 15.8-year period. This is, however, still a matter of active debate.
Gravitational-wave astronomy is an emerging branch of observational astronomy which aims to use gravitational waves to collect observational data about objects such as neutron stars and black holes, events such as supernovae, and processes including those of the early universe shortly after the Big Bang.
A binary black hole (BBH) is a system consisting of two black holes in close orbit around each other. Like black holes themselves, binary black holes are often divided into stellar binary black holes, formed either as remnants of high-mass binary star systems or by dynamic processes and mutual capture; and binary supermassive black holes, believed to be a result of galactic mergers.
The Event Horizon Telescope (EHT) is a large telescope array consisting of a global network of radio telescopes. The EHT project combines data from several very-long-baseline interferometry (VLBI) stations around Earth, which form a combined array with an angular resolution sufficient to observe objects the size of a supermassive black hole's event horizon. The project's observational targets include the two black holes with the largest angular diameter as observed from Earth: the black hole at the center of the supergiant elliptical galaxy Messier 87, and Sagittarius A* at the center of the Milky Way.
In astrophysics, an extreme mass ratio inspiral (EMRI) is the orbit of a relatively light object around a much heavier object, that gradually spirals in due to the emission of gravitational waves. Such systems are likely to be found in the centers of galaxies, where stellar mass compact objects, such as stellar black holes and neutron stars, may be found orbiting a supermassive black hole. In the case of a black hole in orbit around another black hole this is an extreme mass ratio binary black hole. The term EMRI is sometimes used as a shorthand to denote the emitted gravitational waveform as well as the orbit itself.
S5 0014+81 is a distant, compact, hyperluminous, broad-absorption-line quasar, or blazar, located near the high declination region of the constellation Cepheus, near the North Equatorial Pole.
PKS 1302-102 is a quasar in the Virgo constellation, located at a distance of approximately 1.1 Gpc. It has an apparent magnitude of about 14.9 mag in the V band with a redshift of 0.2784. The quasar is hosted by a bright elliptical galaxy, with two neighboring companions at distances of 3 kpc and 6 kpc. The light curve of PKS 1302-102 appears to be sinusoidal with an amplitude of 0.14 mag and a period of 1,884 ± 88 days, which suggests evidence of a supermassive black hole binary.
PSO J030947.49+271757.31, sometimes shortened to PSO J0309+27, is the most distant known blazar, as of 2020. It lies in Aries. The blazar has a redshift of 6.1, meaning its light took almost 13 billion years to reach Earth, when the universe was about 1 billion years old, and its present comoving distance is about 30 billion light-years. It was discovered by a team of researchers led by Silvia Belladitta, a Ph.D. student at the University of Insubria, working for the Italian National Institute for Astrophysics (INAF) in Milan, Italy.
GW190521 was a gravitational wave signal resulting from the merger of two black holes. It was possibly associated with a coincident flash of light; if this association is correct, the merger would have occurred near a third supermassive black hole. The event was observed by the LIGO and Virgo detectors on 21 May 2019 at 03:02:29 UTC, and published on 2 September 2020. The event was 17 billion light years away from Earth, within a 765 deg2 area towards Coma Berenices, Canes Venatici, or Phoenix.
SDSS J1430+2303 is a galaxy with an active galactic nucleus that has been claimed to be undergoing a periodic brightness variability that is speeding up. One explanation for the purported behavior is that it could be a supermassive black hole binary. Initial trajectory models suggested the pair could be merging either before the end of 2022 or, alternatively, within three years.
References
- ↑ O'Neill, S.; et al. (2022). "The Unanticipated Phenomenology of the Blazar PKS 2131–021: A Unique Supermassive Black Hole Binary Candidate". The Astrophysical Journal Letters. 926 (2): 2. doi:10.3847/2041-8213/ac504b. S2CID 242757503.
- ↑ DiCenza, Shawn (2022-03-24). "Astronomers Discover two Supermassive Black Holes Orbiting Each Other, Doomed to Collide in the Future". Universe Today. Retrieved 2022-03-29.
- ↑ "These Two Black Hole Behemoths Will Merge in 10,000 Years". Sky & Telescope. 2022-02-28. Retrieved 2022-03-29.
- ↑ "Colossal Black Holes Locked in Dance at Heart of Galaxy". California Institute of Technology. 2022-02-23. Retrieved 2022-03-29.
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