Many translated example sentences containing "quasar" – German-English dictionary and search engine for German translations. Many translated example sentences containing "quasar" – German-English dictionary and search engine for German translations. Ein Quasar (abgek. auch QSO für Quasi-stellar object) ist der aktive Kern einer Galaxie, der im sichtbaren Bereich des Lichtes nahezu punktförmig (wie ein.
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Quasars this young can reveal information about how galaxies evolved over time. Quasars emit energies of millions, billions, or even trillions of electron volts.
This energy exceeds the total of the light of all the stars within a galaxy. The brightest objects in the universe , they shine anywhere from 10 to , times brighter than the Milky Way.
For instance, if the ancient quasar 3C , one of the brightest objects in the sky, was located 30 light-years from Earth, it would appear as bright as the sun in the sky.
However, quasar 3C , the first quasar to be identified , is 2. It is one of the closest quasars.
Studying quasars has long been a challenge, because of their relationship to the hard-to-measure mass of their supermassive black holes. A new method has begun to weigh the largest of black holes in bulk.
Quasars are part of a class of objects known as active galactic nuclei AGN. Other classes include Seyfert galaxies and blazars. All three require supermassive black holes to power them.
Blazars, like their quasar cousins, put out significantly more energy. Many scientists think that the three types of AGNs are the same objects, but with different perspectives.
While the jets of quasars seem to stream at an angle generally in the direction of Earth, blazars may point their jets directly toward the planet.
The first quasars 3C 48 and 3C were discovered in the late s, as radio sources in all-sky radio surveys.
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 Another radio source, 3C , was predicted to undergo five occultations by the Moon.
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 Hale Telescope on Mount Palomar.
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.
Although the observations and redshifts themselves were not doubted, their correct interpretation was heavily debated, and Bolton's suggestion that the radiation detected from quasars were ordinary spectral lines from distant highly redshifted sources with extreme velocity was not widely accepted at the time.
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, and conflicted with the traditional and predominant Steady State theory of the universe.
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. Schmidt concluded that 3C could either be an individual star around 10km wide within or near to our galaxy, or a distant active galactic nucleus.
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 was due to matter in an accretion disc falling into an supermassive black hole, was only suggested in by Salpeter and Yakov Zel'dovich ,  and even then it was rejected by many astronomers, because the existence of black holes was still widely seen as theoretical and too exotic, in the s, 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 general relativity but rather to light escaping a deep gravitational well special 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.
The uncertainty was such that even as late as , it was stated that "one of the few statements [about Active Galactic Nuclei] to command general agreement has been that the power supply is primarily gravitational",  with the cosmological origin of the redshift being taken as given.
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 that suggest many or even most galaxies have a massive central black hole.
It would also explain why quasars are more common in the early universe: 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,  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, including 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 which reaches the Earth is redshifted due to the metric expansion of space.
Quasars inhabit the center of active galaxies, and are among the most luminous, powerful, and energetic objects known in the universe, emitting up to a thousand times the energy output of the Milky Way , which contains — billion stars.
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.
Most quasars, with the exception of 3C whose average apparent magnitude is 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 .
Light and other radiation cannot escape from within the event horizon of a black hole, but 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 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 that 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 fact, it has been suggested that a quasar could form when the Andromeda Galaxy collides with our own Milky Way galaxy in approximately 3—5 billion years.
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 are known, 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  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. Then in the s, astronomers started to agree on the active galaxy theory as the source of quasars.
That, in fact, several different kinds of objects: And that some mechanism was causing galaxies to blast out jets of radiation from their cores.
Gas and dust likely form a torus around the central black hole, with clouds of charged gas above and below. When material gets too close, it forms an accretion disk around the black hole.
It heats up to millions of degrees, blasting out an enormous amount of radiation. The magnetic environment around the black hole forms twin jets of material which flow out into space for millions of light-years.
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