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These black holes grow in step with the mass of stars in their host galaxy in a way not understood at present.

One idea is that jets, radiation and winds created by the quasars, shut down the formation of new stars in the host galaxy, a process called 'feedback'.

The jets that produce strong radio emission in some quasars at the centers of clusters of galaxies are known to have enough power to prevent the hot gas in those clusters from cooling and falling onto the central galaxy.

Quasars' luminosities are variable, with time scales that range from months to hours. This means that quasars generate and emit their energy from a very small region, since each part of the quasar would have to be in contact with other parts on such a time scale as to allow the coordination of the luminosity variations.

This would mean that a quasar varying on a time scale of a few weeks cannot be larger than a few light-weeks across.

The emission of large amounts of power from a small region requires a power source far more efficient than the nuclear fusion that powers stars.

Stellar explosions such as supernovas and gamma-ray bursts , and direct matter - antimatter annihilation, can also produce very high power output, but supernovae only last for days, and the universe does not appear to have had large amounts of antimatter at the relevant times.

Since quasars exhibit all the properties common to other active galaxies such as Seyfert galaxies , the emission from quasars can be readily compared to those of smaller active galaxies powered by smaller supermassive black holes.

The brightest known quasars devour solar masses of material every year. The largest known is estimated to consume matter equivalent to Earths per minute.

Quasar luminosities can vary considerably over time, depending on their surroundings. Since it is difficult to fuel quasars for many billions of years, after a quasar finishes accreting the surrounding gas and dust, it becomes an ordinary galaxy.

Radiation from quasars is partially 'nonthermal' i. Extremely high energies might be explained by several mechanisms see Fermi acceleration and Centrifugal mechanism of acceleration.

Quasars can be detected over the entire observable electromagnetic spectrum including radio , infrared , visible light , ultraviolet , X-ray and even gamma rays.

Most quasars are brightest in their rest-frame near-ultraviolet wavelength of A minority of quasars show strong radio emission, which is generated by jets of matter moving close to the speed of light.

When viewed downward, these appear as blazars and often have regions that seem to move away from the center faster than the speed of light superluminal expansion.

This is an optical illusion due to the properties of special relativity. Quasar redshifts are measured from the strong spectral lines that dominate their visible and ultraviolet emission spectra.

These lines are brighter than the continuous spectrum. They exhibit Doppler broadening corresponding to mean speed of several percent of the speed of light.

Fast motions strongly indicate a large mass. Emission lines of hydrogen mainly of the Lyman series and Balmer series , helium, carbon, magnesium, iron and oxygen are the brightest lines.

The atoms emitting these lines range from neutral to highly ionized, leaving it highly charged. This wide range of ionization shows that the gas is highly irradiated by the quasar, not merely hot, and not by stars, which cannot produce such a wide range of ionization.

Like all unobscured active galaxies, quasars can be strong X-ray sources. Radio-loud quasars can also produce X-rays and gamma rays by inverse Compton scattering of lower-energy photons by the radio-emitting electrons in the jet.

Quasars also provide some clues as to the end of the Big Bang 's reionization. More recent quasars show no absorption region but rather their spectra contain a spiky area known as the Lyman-alpha forest ; this indicates that the intergalactic medium has undergone reionization into plasma , and that neutral gas exists only in small clouds.

The intense production of ionizing ultraviolet radiation is also significant, as it would provide a mechanism for reionization to occur as galaxies form.

Quasars show evidence of elements heavier than helium , indicating that galaxies underwent a massive phase of star formation , creating population III stars between the time of the Big Bang and the first observed quasars.

Light from these stars may have been observed in using NASA 's Spitzer Space Telescope , [49] although this observation remains to be confirmed. The taxonomy of quasars includes various subtypes representing subsets of the quasar population having distinct properties.

Because quasars are extremely distant, bright, and small in apparent size, they are useful reference points in establishing a measurement grid on the sky.

Because they are so distant, they are apparently stationary to our current technology, yet their positions can be measured with the utmost accuracy by very-long-baseline interferometry VLBI.

The positions of most are known to 0. A multiple-image quasar is a quasar whose light undergoes gravitational lensing , resulting in double, triple or quadruple images of the same quasar.

As quasars are rare objects, the probability of three or more separate quasars being found near the same location is very low.

The first true triple quasar was found in by observations at the W. Keck Observatory Mauna Kea , Hawaii. When astronomers discovered the third member, they confirmed that the sources were separate and not the result of gravitational lensing.

The first quadruple quasar was discovered in When two quasars are so nearly in the same direction as seen from Earth that they appear to be a single quasar but may be separated by the use of telescopes, they are referred to as a "double quasar", such as the Twin Quasar.

This configuration is similar to the optical double star. Two quasars, a "quasar pair", may be closely related in time and space, and be gravitationally bound to one another.

These may take the form of two quasars in the same galaxy cluster. This configuration is similar to two prominent stars in a star cluster.

A "binary quasar", may be closely linked gravitationally and form a pair of interacting galaxies. This configuration is similar to that of a binary star system.

From Wikipedia, the free encyclopedia. This article is about the astronomical object. For other uses, see Quasar disambiguation. It is not to be confused with quasi-star.

Redshift , Metric expansion of space , and Universe. Reionization and Chronology of the Universe. Retrieved 4 July Retrieved 5 March Retrieved 6 December Explicit use of et al.

Most Distant Black Hole". The Publications of the Astronomical Society of the Pacific. Retrieved 3 October Publications of the Astronomical Society of the Pacific.

Retrieved 22 March Isodual theory of antimatter: Black hole models for active galactic nuclei , The University of Alabama. You Won't Feel a Thing".

Retrieved 20 November Relativity, Gravitation and Cosmology Illustrated ed. Archived from the original PDF on December 17, Retrieved December 30, Archived from the original PDF on February 2, Retrieved July 1, Barthel, Is every Quasar beamed?

Retrieved 26 October Retrieved 4 November Archived from the original on The Astrophysical Journal Letters. The Nature of Cosmological Ionizing Source".

News of light that may be from population III stars". Selection and Optical Properties of a Sample at 0. Retrieved 13 July Naval Observatory Astronomical Applications.

Annual Review of Astronomy and Astrophysics. Retrieved 19 June Discovery of a Physical Quasar Triplet". Monthly Notices of the Royal Astronomical Society.

Retrieved 9 February Gravitational singularity Penrose—Hawking singularity theorems Primordial black hole Gravastar Dark star Dark-energy star Black star Eternally collapsing object Magnetospheric eternally collapsing object Fuzzball White hole Naked singularity Ring singularity Immirzi parameter Membrane paradigm Kugelblitz Wormhole Quasi-star.

Black holes Most massive Nearest Quasars. Astronomy portal Space portal. Retrieved from " https: Active galaxy types Quasars Radio astronomy.

Because of the finite speed of light , when quasars are observed at great distances, they are observed as they were in the distant past.

Thus, the increasing density of quasars with distance means that they were more common in the past than they are now.

At earlier ages, the number density of quasars decreases sharply, corresponding to an era when the quasar population was still building up.

The most distant, and thus earliest, quasars known were formed less than a billion years after the big bang. Individual quasars appear as their central black holes begin to accrete gas at a high rate, possibly triggered by a merger with another galaxy, building up the mass of the central black hole.

The current best estimate is that quasar activity is episodic, with individual episodes lasting around a million years and the total quasar lifetime lasting around 10 million years.

At some point, quasar activity ceases completely, leaving behind the dormant massive black holes found in most massive galaxies. Indeed, in the current universe the remaining AGN population is made up predominantly of lower-luminosity Seyfert galaxies with relatively small supermassive black holes.

In the present-day universe there is a close relationship between the mass of a black hole and the mass of its host galaxy.

This is quite remarkable, since the central black hole accounts for only about 0. It is believed that the intense radiation, mass outflows, and jets from the black hole during its active quasar phase are responsible.

The radiation, outflows, and jets heat up and can even remove entirely the interstellar medium from the host galaxy.

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QSO, quasi-stellar radio source. Learn More in these related Britannica articles: The discovery of quasars quasi-stellar radio sources in the early s also told heavily against the steady-state theory.

Quasar s were first identified as strong radio sources that in visible light appear to be identified with small starlike objects. Further, they have large redshifts, which implies that they are….

Quasar s are objects whose spectra display very large redshifts, thus implying in accordance with the Hubble law that they lie at the greatest distances see above Determining astronomical distances.

They were discovered in but remained enigmatic for many years. They appear as starlike i. These cosmic objects have intense clouds of radio emission that extend hundreds of thousands of light-years away from a central energy source located in an active galactic nucleus AGN , or quasar.

Observations with high-resolution radio arrays show…. Luminosity , in astronomy, the amount of light emitted by an object in a unit of time.

The luminosity of the Sun is 3. Quasars active galaxies In active galactic nucleus classification of galaxies In galaxy: Other classification schemes and galaxy types history of astronomy In astronomy: The steady-state challenge luminosity In galaxy: Luminosity observational astronomy In astronomy: Study of other galaxies and related phenomena radio sources In radio and radar astronomy In radio source radio telescopes In radio telescope: Major applications of radio telescopes redshift In redshift View More.

Articles from Britannica Encyclopedias for elementary and high school students. Help us improve this article! Contact our editors with your feedback.

Introduction Discovery of quasars Finding quasars Physical structure of quasars Evolution of quasars. You may find it helpful to search within the site to see how similar or related subjects are covered.

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