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Astronomen haben den bislang entferntesten Quasar entdeckt – das Licht Im Zentrum des Quasars befindet sich ein Schwarzes Loch mit Ein Quasar ist der aktive Kern einer Galaxie, der im sichtbaren Bereich des Lichts nahezu punktförmig erscheint und sehr große Energiemengen in anderen Wellenlängenbereichen ausstrahlt. Quasar vs. QSO. Klären wir zunächst die Namen: Quasar ist ein Kunstwort aus quasi-stellare Radioquelle, d.h. Quasare sind radio-laut (hohe Radioleuchtkraft).

Quasar Quasare, Schwarze Löcher und das Alter des Universums

Ein Quasar ist der aktive Kern einer Galaxie, der im sichtbaren Bereich des Lichts nahezu punktförmig erscheint und sehr große Energiemengen in anderen Wellenlängenbereichen ausstrahlt. Quasar vs. QSO. Klären wir zunächst die Namen: Quasar ist ein Kunstwort aus quasi-stellare Radioquelle, d.h. Quasare sind radio-laut (hohe Radioleuchtkraft). Ein Quasar ist ein akkreditierendes Schwarzes Loch im Zentrum einer Galaxie, ein Schwarzes Loch mit einer großen Menge Gas um es herum. • Quasare sind. Doch gibt es Hinweise, dass Quasare entstehen, weil Gase im Zentrum einer Galaxie von einem schwarzen Loch verschlungen werden. [1] Leuchtende Galaxien. Astronomen haben den bislang entferntesten Quasar entdeckt – das Licht Im Zentrum des Quasars befindet sich ein Schwarzes Loch mit Was ist ein Quasar und was macht so ein Objekt? Wie hat man die Entfernung bestimmt? Und hat diese Entdeckung Konsequenzen für unser. Ein Quasar besteht vermutlich aus einem Schwarzen Loch umgeben von einer Scheibe leuchtender Materie. Entdeckung und Namensgebung. Fotografische.

Quasar

Doch gibt es Hinweise, dass Quasare entstehen, weil Gase im Zentrum einer Galaxie von einem schwarzen Loch verschlungen werden. [1] Leuchtende Galaxien. Ein Quasar ist ein akkreditierendes Schwarzes Loch im Zentrum einer Galaxie, ein Schwarzes Loch mit einer großen Menge Gas um es herum. • Quasare sind. Astronomen haben den bislang entferntesten Quasar entdeckt – das Licht Im Zentrum des Quasars befindet sich ein Schwarzes Loch mit

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Applying Hubble's law to these redshifts, it can be shown that they are between million [46] and Because of the great distances to the farthest quasars and the finite velocity of light, they and their surrounding space appear as they existed in the very early universe.

The power of quasars originates from supermassive black holes that are believed to exist at the core of most galaxies.

The Doppler shifts of stars near the cores of galaxies indicate that they are rotating around tremendous masses with very steep gravity gradients, suggesting black holes.

Although quasars appear faint when viewed from Earth, they are visible from extreme distances, being the most luminous objects in the known universe.

It has an average apparent magnitude of In a universe containing hundreds of billions of galaxies, most of which had active nuclei billions of years ago but only seen today, it is statistically certain that thousands of energy jets should be pointed toward the Earth, some more directly than others.

In many cases it is likely that the brighter the quasar, the more directly its jet is aimed at the Earth. Such quasars are called blazars.

Quasars were much more common in the early universe than they are today. This discovery by Maarten Schmidt in was early strong evidence against Steady-state cosmology and in favor of the Big Bang cosmology.

Quasars show the locations where massive black holes are growing rapidly by accretion. 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 10 Earths per second.

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 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 , [56] 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 grouping of two or more quasars on the sky can result from a chance alignment, where the quasars are not physically associated, from actual physical proximity, or from the effects of gravity bending the light of a single quasar into two or more images by gravitational lensing.

When two quasars appear to be very close to each other as seen from Earth separated by a few arcseconds or less , they are commonly referred to as a "double quasar".

When the two are also close together in space i. As quasars are overall rare objects in the universe, the probability of three or more separate quasars being found near the same physical location is very low, and determining whether the system is closely separated physically requires significant observational effort.

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.

A multiple-image quasar is a quasar whose light undergoes gravitational lensing , resulting in double, triple or quadruple images of the same quasar.

From Wikipedia, the free encyclopedia. Active galactic nucleus containing a supermassive black hole. This article is about the astronomical object.

For other uses, see Quasar disambiguation. It is not to be confused with quasi-star. Main articles: Redshift , Metric expansion of space , and Universe.

Play media. Main articles: Reionization and Chronology of the Universe. Astronomy portal Space portal. ESO Science Release. Retrieved 4 July Bibcode : Natur.

February Accretion Power in Astrophysics Third ed. Bibcode : apa.. Retrieved The Astrophysical Journal. Bibcode : ApJ The Astronomical Journal.

Bibcode : AJ Retrieved 6 December Gemini Observatory. The Astrophysical Journal Letters. Physics Today. Bibcode : PhT Archived from the original on The Publications of the Astronomical Society of the Pacific.

Bibcode : PASP.. Retrieved 3 October European Space Agency. Astrophysical Journal. Physics: Imagination and Reality.

Jodrell Bank Observatory. Shields The Discovery Of Quasars". Publications of the Astronomical Society of the Pacific.

Chandrasekhar Greenstein ; M. Schmidt Gray That's weird! Golden, Colo. Dordrecht: Springer. Bibcode : itaa.

Energy Source". October The University of Alabama. Jun 20, Science News. Retrieved 20 November Altri progetti. Da Wikipedia, l'enciclopedia libera.

Disambiguazione — Se stai cercando altri significati, vedi Quasar disambigua. Barthel, Is every Quasar beamed?

Altri progetti Wikizionario Wikimedia Commons. Portale Fisica. Portale Oggetti del profondo cielo. Categorie : Oggetti astronomici Cosmologia Quasar.

Menu di navigazione Strumenti personali Accesso non effettuato discussioni contributi registrati entra. Namespace Voce Discussione. Visite Leggi Modifica Modifica wikitesto Cronologia.

Wikimedia Commons. Lo stesso argomento in dettaglio: 3C Lo stesso argomento in dettaglio: TON

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The power radiated by quasars is enormous; the most powerful quasars have luminosities thousands of times greater than a galaxy such as the Milky Way.

The redshifts of quasars are of cosmological origin. The term quasar originated as a contraction of quasi-stellar [star-like] radio source — because quasars were first identified during the s as sources of radio-wave emission of unknown physical origin — and when identified in photographic images at visible wavelengths, they resembled faint, star-like points of light.

High-resolution images of quasars, particularly from the Hubble Space Telescope , have demonstrated that quasars occur in the centers of galaxies, and that some host galaxies are strongly interacting or merging galaxies.

Quasars are found over a very broad range of distances, and quasar discovery surveys have demonstrated that quasar activity was more common in the distant past.

The peak epoch of quasar activity was approximately 10 billion years ago. The supermassive black hole in this quasar, estimated at million solar masses , is the most distant black hole identified to date.

The term "quasar" was first used in an article by Chinese-American astrophysicist Hong-Yee Chiu in May , in Physics Today , to describe certain astronomically-puzzling objects: [12].

So far, the clumsily long name "quasi-stellar radio sources" is used to describe these objects. Because the nature of these objects is entirely unknown, it is hard to prepare a short, appropriate nomenclature for them so that their essential properties are obvious from their name.

For convenience, the abbreviated form "quasar" will be used throughout this paper. Between and , it became clear from work by Heber Curtis , Ernst Öpik and others, that some objects " nebulae " seen by astronomers were in fact distant galaxies like our own.

But when radio astronomy commenced in the s, astronomers detected, among the galaxies, a small number of anomalous objects with properties that defied explanation.

The objects emitted large amounts of radiation of many frequencies, but no source could be located optically, or in some cases only a faint and point-like object somewhat like a distant star.

The spectral lines of these objects, which identify the chemical elements of which the object is composed, were also extremely strange and defied explanation.

Some of them changed their luminosity very rapidly in the optical range and even more rapidly in the X-ray range, suggesting an upper limit on their size, perhaps no larger than our own Solar System.

They were described as "quasi-stellar [meaning: star-like] radio sources" , or "quasi-stellar objects" QSOs , a name which reflected their unknown nature, and this became shortened to "quasar".

Using small telescopes and the Lovell Telescope as an interferometer, they were shown to have a very small angular size.

In , a definite identification of the radio source 3C 48 with an optical object was published by Allan Sandage and Thomas A. Astronomers had detected what appeared to be a faint blue star at the location of the radio source and obtained its spectrum, which contained many unknown broad emission lines.

The anomalous spectrum defied interpretation. British-Australian astronomer John Bolton made many early observations of quasars, including a breakthrough in Measurements taken by Cyril Hazard and John Bolton during one of the occultations using the Parkes Radio Telescope allowed Maarten Schmidt to find a visible counterpart to the radio source and obtain an optical spectrum using the inch 5.

This spectrum revealed the same strange emission lines. Schmidt was able to demonstrate that these were likely to be the ordinary spectral lines of hydrogen redshifted by Although it raised many questions, Schmidt's discovery quickly revolutionized quasar observation.

Shortly afterwards, two more quasar spectra in and five more in were also confirmed as ordinary light that had been redshifted to an extreme degree.

An extreme redshift could imply great distance and velocity but could also be due to extreme mass or perhaps some other unknown laws of nature.

Extreme velocity and distance would also imply immense power output, which lacked explanation. The small sizes were confirmed by interferometry and by observing the speed with which the quasar as a whole varied in output, and by their inability to be seen in even the most powerful visible-light telescopes as anything more than faint starlike points of light.

But if they were small and far away in space, their power output would have to be immense and difficult to explain.

Equally, if they were very small and much closer to our galaxy, it would be easy to explain their apparent power output, but less easy to explain their redshifts and lack of detectable movement against the background of the universe.

Schmidt noted that redshift is also associated with the expansion of the universe, as codified in Hubble's law. If the measured redshift was due to expansion, then this would support an interpretation of very distant objects with extraordinarily high luminosity and power output, far beyond any object seen to date.

This extreme luminosity would also explain the large radio signal. He stated that a distant and extremely powerful object seemed more likely to be correct.

Schmidt's explanation for the high redshift was not widely accepted at the time. A major concern was the enormous amount of energy these objects would have to be radiating, if they were distant.

In the s no commonly accepted mechanism could account for this. The currently accepted explanation, that it is due to matter in an accretion disc falling into a supermassive black hole , was only suggested in by Edwin Salpeter and Yakov Zel'dovich , [23] and even then it was rejected by many astronomers, because in the s, the existence of black holes was still widely seen as theoretical and too exotic, and because it was not yet confirmed that many galaxies including our own have supermassive black holes at their center.

The strange spectral lines in their radiation, and the speed of change seen in some quasars, also suggested to many astronomers and cosmologists that the objects were comparatively small and therefore perhaps bright, massive and not far away; accordingly that their redshifts were not due to distance or velocity, and must be due to some other reason or an unknown process, meaning that the quasars were not really powerful objects nor at extreme distances, as their redshifted light implied.

A common alternative explanation was that the redshifts were caused by extreme mass gravitational redshifting explained by general relativity and not by extreme velocity explained by special relativity.

Various explanations were proposed during the s and s, each with their own problems. It was suggested that quasars were nearby objects, and that their redshift was not due to the expansion of space special relativity but rather to light escaping a deep gravitational well general relativity.

This would require a massive object, which would also explain the high luminosities. However, a star of sufficient mass to produce the measured redshift would be unstable and in excess of the Hayashi limit.

One strong argument against them was that they implied energies that were far in excess of known energy conversion processes, including nuclear fusion.

There were some suggestions that quasars were made of some hitherto unknown form of stable antimatter regions and that this might account for their brightness.

Eventually, starting from about the s, many lines of evidence including the first X-ray space observatories , knowledge of black holes and modern models of cosmology gradually demonstrated that the quasar redshifts are genuine and due to the expansion of space , that quasars are in fact as powerful and as distant as Schmidt and some other astronomers had suggested, and that their energy source is matter from an accretion disc falling onto a supermassive black hole.

This model also fits well with other observations suggesting that many or even most galaxies have a massive central black hole.

It would also explain why quasars are more common in the early universe: as a quasar draws matter from its accretion disc, there comes a point when there is less matter nearby, and energy production falls off or ceases, as the quasar becomes a more ordinary type of galaxy.

The accretion-disc energy-production mechanism was finally modeled in the s, and black holes were also directly detected including evidence showing that supermassive black holes could be found at the centers of our own and many other galaxies , which resolved the concern that quasars were too luminous to be a result of very distant objects or that a suitable mechanism could not be confirmed to exist in nature.

By it was "well accepted" that this was the correct explanation for quasars, [31] and the cosmological distance and energy output of quasars was accepted by almost all researchers.

Hence the name "QSO" quasi-stellar object is used in addition to "quasar" to refer to these objects, further categorised into the "radio-loud" and the "radio-quiet" classes.

The discovery of the quasar had large implications for the field of astronomy in the s, including drawing physics and astronomy closer together.

It is now known that quasars are distant but extremely luminous objects, so any light that reaches the Earth is redshifted due to the metric expansion of space.

This radiation is emitted across the electromagnetic spectrum, almost uniformly, from X-rays to the far infrared with a peak in the ultraviolet optical bands, with some quasars also being strong sources of radio emission and of gamma-rays.

With high-resolution imaging from ground-based telescopes and the Hubble Space Telescope , the "host galaxies" surrounding the quasars have been detected in some cases.

Quasars are believed—and in many cases confirmed—to be powered by accretion of material into supermassive black holes in the nuclei of distant galaxies, as suggested in by Edwin Salpeter and Yakov Zel'dovich.

The energy produced by a quasar is generated outside the black hole, by gravitational stresses and immense friction within the material nearest to the black hole, as it orbits and falls inward.

Central masses of 10 5 to 10 9 solar masses have been measured in quasars by using reverberation mapping.

Several dozen nearby large galaxies, including our own Milky Way galaxy, that do not have an active center and do not show any activity similar to a quasar, are confirmed to contain a similar supermassive black hole in their nuclei galactic center.

Thus it is now thought that all large galaxies have a black hole of this kind, but only a small fraction have sufficient matter in the right kind of orbit at their center to become active and power radiation in such a way as to be seen as quasars.

This also explains why quasars were more common in the early universe, as this energy production ends when the supermassive black hole consumes all of the gas and dust near it.

This means that it is possible that most galaxies, including the Milky Way, have gone through an active stage, appearing as a quasar or some other class of active galaxy that depended on the black-hole mass and the accretion rate, and are now quiescent because they lack a supply of matter to feed into their central black holes to generate radiation.

The matter accreting onto the black hole is unlikely to fall directly in, but will have some angular momentum around the black hole, which will cause the matter to collect into an accretion disc.

Quasars may also be ignited or re-ignited when normal galaxies merge and the black hole is infused with a fresh source of matter. In the s, unified models were developed in which quasars were classified as a particular kind of active galaxy , and a consensus emerged that in many cases it is simply the viewing angle that distinguishes them from other active galaxies, such as blazars and radio galaxies.

More than quasars have been found [45] , most from the Sloan Digital Sky Survey. All observed quasar spectra have redshifts between 0.

Applying Hubble's law to these redshifts, it can be shown that they are between million [46] and Because of the great distances to the farthest quasars and the finite velocity of light, they and their surrounding space appear as they existed in the very early universe.

The power of quasars originates from supermassive black holes that are believed to exist at the core of most galaxies.

The Doppler shifts of stars near the cores of galaxies indicate that they are rotating around tremendous masses with very steep gravity gradients, suggesting black holes.

Although quasars appear faint when viewed from Earth, they are visible from extreme distances, being the most luminous objects in the known universe.

It has an average apparent magnitude of In a universe containing hundreds of billions of galaxies, most of which had active nuclei billions of years ago but only seen today, it is statistically certain that thousands of energy jets should be pointed toward the Earth, some more directly than others.

In many cases it is likely that the brighter the quasar, the more directly its jet is aimed at the Earth. Such quasars are called blazars.

Quasars were much more common in the early universe than they are today. This discovery by Maarten Schmidt in was early strong evidence against Steady-state cosmology and in favor of the Big Bang cosmology.

Quasars show the locations where massive black holes are growing rapidly by accretion. 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 10 Earths per second.

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 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.

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