A quasar ( ) (also known as QSO or quasi-star-object ) is a very glowing active galaxy core (AGN). Most large galaxies contain supermassive central black holes with masses ranging from millions to billions of Sun's mass. In quasars and other AGN types, black holes are surrounded by gas accretion disks. When the gas in the accretion plate falls into the black hole, energy is released in the form of electromagnetic radiation. This radiation can be observed throughout the electromagnetic spectrum in radio, infrared, visible, ultraviolet, and X-ray, and gamma wavelength. The power emitted by quasars is enormous: the most powerful quasars have a luminosity that exceeds 10 watts, thousands of times larger than ordinary large galaxies like the Milky Way.
The term "quasars" originates as quasi-stellar contrast [air-like] radio sources , since the quasars were first identified during the 1950s as the source of the radio wave emission of unknown physical origin, and when identified in photographic images at visible wavelengths they resemble light dots like stars. High-resolution images of quasars, particularly from the Hubble Space Telescope, have shown that quasars occur in galaxy centers, and that some galaxies host quasars interact or interact with galaxies. Like other AGN categories, the observed properties of quasars depend on many factors including black hole mass, gas acceleration rate, disk accretion orientation relative to the observer, jet presence, and degree of blurring by gas and dust within the host galaxy.
Quasars are found over a very wide range (corresponding to a redshift from z & lt; 0.1 for the nearest quasar to z & gt; 7 for the most distant quasars known), and the quasar discovery survey has shown that quasar activity is more common in distant past. The peak period of quasar activity in the Universe relates to a redshift of about 2, or about 10 billion years ago. By 2017, the most distant quasars are ULAS J1342 0928 in redshift z = 7.54; the observed light of this quasar is emitted when the Universe is only 690 million years old. This supermassive black hole in quasars is the farthest black hole identified to date, and is thought to have a mass that is 800 million times the mass of our Sun.
Video Quasar
Naming
The term "quasars" was invented by the Hong-Yee Chiu-born US astrophysicist in May 1964, in Today's Physics, to describe certain confusing astronomical objects:
So far, the long name of the clumsy quasi-star radio source is used to describe these objects. Because the nature of these objects is completely unknown, it is difficult to prepare short, appropriate nomenclature for them so that their essential qualities are clear from their names. For convenience, a concise 'quasar' form will be used throughout this paper.
Maps Quasar
History of observation and interpretation
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Between 1917 and 1922, it became clear from work by Heber Curtis, Ernst ÃÆ' â € "pik and others, that some objects (" nebulae ") seen by astronomers are actually distant galaxies like our own galaxy. But when radio astronomy began in the 1950s, astronomers detected, among galaxies, a small number of anomalous objects with opposing explanatory properties.
Objects emit a large amount of radiation from many frequencies, but no source can be found optically, or in some cases only a vague object and such a point that is somewhat like a distant star. The spectral lines of these objects, which identify the chemical elements that are the object, are also very strange and challenging explanations. Some of them change their luminosity very quickly in the optical range and even faster in the X-ray range, indicating an upper limit on their size, probably no bigger than our own Solar System. This implies a very high power density. A lot of discussion about these objects. They are described as "quasi-stellar [ie: star-like] radio sources" , or "quasi-star objects" (QSOs), names that reflect their unknown nature, and this becomes shortened to "quasars".
Initial observation (1960s and earlier)
The first quasar (3C 48 and 3C 273) was discovered in the late 1950s, as a radio source in a radio survey of all the skies. They were first recorded as a radio source with no visible objects connected. Using a small telescope and Lovell Telescope as an interferometer, they proved to have very small angular sizes. Hundreds of these objects were recorded by 1960 and published in the Third Cambridge Catalog as astronomers observing the sky for their optical counterparts. In 1963, the exact identification of 3C 48 radio sources with optical objects was published by Allan Sandage and Thomas A. Matthews. Astronomers have detected what appears to be a faint blue star at a radio source location and obtains its spectrum, which contains many unknown broad emission lines. The spectrum of anomalies defies interpretation.
The British-Australian astronomer John Bolton made many preliminary observations of quasars, including a breakthrough in 1962. Another radio source, 3C 273, is predicted to undergo five occultations by the Moon. Measurements made by Cyril Hazard and John Bolton during one of the occultations using Parkes Radio Telescope enabled Maarten Schmidt to find a visible partner from a radio source and obtained an optical spectrum using the Hale 200 Telescope on Mount Palomar. This spectrum reveals the same strange emission line. Schmidt was able to demonstrate that this might be a commonly reduced-spectrum hydrogen spectrum of 15.8 percent - an extreme redshift that had not been seen in previous astronomy. If this is due to the physical movement of the "star", then 3C 273 is receding at high speed, about 47,000 km/sec, well beyond the known star velocity and opposing clear explanations. Nor will it help to extreme speed to explain the big radio emission 3C 273.
Although it raises many questions, Schmidt's invention quickly revolutionized the observations of quasars. The strange spectrum of 3C 48 was quickly identified by Schmidt, Greenstein and Oke as hydrogen and magnesium redshifted by 37%. Shortly after, the two quasar spectra again in 1964 and five again in 1965, were also confirmed as ordinary lights that had been moved to an extreme degree.
Although the observations and redshifts themselves are undoubtedly the correct interpretation is highly contested, and Bolton's suggestion that the radiation detected from the quasars is a regular spectral line from a source deeply redshifted away with extreme speed was not widely accepted at the time.
Development of physical understanding (1960s)
One of the major debate topics during the 1960s was how to interpret redshifted light and a relatively small size visible with quasars. Schmidt's discovery that quasar redshifts can be described as ordinary spectral lines are revived at enormous quantities, quickly raising more questions than can be answered.
Extreme red movements can imply large distances and velocities, but can also be due to extreme mass, or perhaps some unknown natural laws. Extreme speed and distance will also imply enormous power output, which has no explanation, and contradicts the traditional and dominant Steady State theory of the universe. The small size is confirmed by interferometry and by observing the velocity of the quasars as a whole varies in output, and by their inability to be seen even in the most powerful looking light telescope as something more than a point of light like a star. But if they are small, the power output becomes more difficult to explain. If quasars are very small and close to our galaxy, it will be easy to explain the obvious power output, but it is less easy to explain their red shift and the lack of detectable motion against the background of the universe.
Various explanations are submitted over time. It is suggested, for example, that the redshift of quasars is not due to space extension but rather to light coming out of deep gravity wells. But a star of mass sufficient to form such a well would become unstable and exceed Hayashi's limit. Quasars also exhibit prohibited spectrum emission lines previously only seen in hot density gas nebulae, which would be too diffuse to produce observed strength and enter deep gravity wells. There are also serious concerns about the idea of ​​distant cosmological quasars. One strong argument against them is that they imply energy far beyond the known energy conversion process, including nuclear fusion. At the present time, there are some suggestions that quasars are made of some form of stable antimatter that is hitherto unknown and this might explain their brilliance. Others speculate that quasars are the ends of the white holes of wormholes, or chain reactions of many supernovas.
Schmidt notes that redshift is also associated with the expansion of the universe, as codified in Hubble's law. If the redshift measured is due to expansion, then the object must be very far away. In this case, it must have a very high luminosity, just outside the visible object to this day. This extreme luminosity will also explain the large radio signals. Schmidt concludes the quasars very far, very bright objects.
Schmidt's explanation for high redshift was not widely accepted at the time. Another explanation offered is that it is the gravity redshift being measured; this will require a large object that also explains the high luminosity. A star large enough to produce a measurable redshift would far exceed the Hayashi limit. Several other mechanisms are also proposed, each with their own problems.
The main concern is the enormous amount of energy these things must emit, if the distance is far away. There is no general accepted mechanism that can explain this. The correct explanation, that it is because of the material in the accretion of disks that fall into supermassive black holes, was only suggested in 1964 by Salpeter and Yakov Zel'dovich, and even then it was rejected by many astronomers, since the existence of black holes is still widely seen as theoretical and too exotic in the 1960s, and since it has not been confirmed that many galaxies (including our galaxy) have supermassive black holes at their center. The strange spectral lines in their radiation, and the rate of change seen in some quasars, also suggest to many astronomers and cosmologists that they are relatively small and therefore may be light, massive and not far away; therefore their redshifts are not due to distance or speed, and must be due to some other reason or unknown process, which means that quasars are not really strong objects or at extreme distances, as their redshifted lights are implied. A common alternative explanation is that redshifts are caused by extreme mass (redshifting gravity explained by general relativity) and not by extreme speed (explained by special relativity). In 1984, it was stated that "one of the few statements [about Galactic Nuclei Active] for a general agreement is that the power supply is primarily gravity", with the cosmological origin of the redshift taken as granted.
Finally, starting from around the 1970s, many lines of evidence (including the first X-Ray space observatory, knowledge of black holes and modern models of cosmology) gradually show that quasar redshifts are original, and because of space extensions, quasars are actually just as powerful and as close as suggested by Schmidt and some other astronomers, and that their energy source is the material of the accretion disk that falls into a supermassive black hole. These include important evidence of optics and X-Ray viewing galaxies hosted quasars, finding an intervening 'absorption path' explaining various spectral anomalies, observations of gravitational lens, Peterson and Gunn 1971 found that galaxies containing quasars show the same red shift as quasars, and Christianity's 1973 findings that "fuzzy" around many quasars are consistent with host galaxies that are less luminous.
This model also fits with other observations that show many or even most galaxies have large central black holes. This will also explain why quasars are more common in the early universe: when quasars pull material from their accretion disks, there will be a point where there is less material nearby, and energy production falls or vanishes as quasars become more commonplace types of galaxies.
The mechanism of energy production of accretion discs was eventually modeled in the 1970s, and black holes were also directly detected (including evidence suggesting that supermassive black holes can be found at the center of our own galaxy and many others), which resolves concerns that the quasars are too bright to be results from very distant objects or that matching mechanisms can not be confirmed to exist in nature. In 1987, "well received" that this was the correct explanation for quasars, and the cosmological distance and quasar energy output were accepted by almost all researchers.
Modern observations (the 1970s onwards)
It has been found that not all quasars have strong radio emissions; actually only about 10% are "radio-loud". Therefore the name 'QSO' (quasi-star object) is used (other than "quasar") to refer to these objects, including 'radio-hard' and 'radio-quiet' classes. The discovery of quasars has major implications for the field of astronomy in the 1960s, including drawing physics and astronomy more closely.
In 1979 the effect of gravitational lens predicted by Einstein's Theory of Relativity was confirmed by observation for the first time with the image of a double quasar 0957 561.
Current understanding
It is now known that quasars are distant but very luminous objects, so that every light reaching the Earth changes color because of the expansion of the metric space.
Quasars inhabit the center of active galaxies, and are one of the brightest, strongest and energetic objects known in the universe, emitting up to 1,000 times the Milky Way's energy output, which contains 200-400 billion stars. This radiation is emitted across the electromagnetic spectrum, almost uniformly, from X-rays to far-infrared with peaks in ultraviolet-optical bands, with some quasars also being a powerful source of radio emissions and gamma rays. With high-resolution imaging of ground-based telescopes and the Hubble Space Telescope, the "host galaxy" surrounding the quasars has been detected in some cases. These galaxies are usually too dim to be seen against the glare of quasars, except with special techniques. Most quasars, with the exception of 3C 273 whose average magnitude seems to be 12.9, can not be seen with a small telescope.
Quasars are believed - and in many cases confirmed - to be supported by the increment of matter into supermassive black holes in the nuclei of distant galaxies. Light and other radiation can not escape from within the horizon of the black hole event, but the energy produced by the quasars is produced outside the black hole, by the gravitational pressure and the great friction within the material closest to the black. hole, as it orbits and falls into. The large luminosity of quasars results from the accretion discs from the center of supermassive black holes, which can convert between 6% and 32% of the mass of objects into energy, compared to only 0.7% for the nuclear fusion process of the pp chains that dominate energy. production in stars like the Sun. The middle mass of 10 5 to 10 9 solar masses has been measured in quasars by using echo mapping. Several dozen large galaxies nearby - including our own Milky Way galaxy, which has no active center and shows no activity similar to quasars, are confirmed to contain similar supermassive black holes in their nucleus (galactic center), so it now thinks that all galaxies large have this kind of black hole, but only a small part that has enough material in the right orbit at its center, becomes active and radiation power in this way. This is the activity of black holes that are seen as quasars.
It also explains why quasars are more common in the early universe, because this energy production ends when supermassive black holes spend all the gas and dust nearby. This means that it is possible that most galaxies, including the Milky Way, have gone through an active stage, appearing as quasars or some other active galaxy class that depends on the mass of the black hole and the level of accretion, and are now silent as they lack the supply of material to be inserted into the black hole center them to produce radiation.
Problems that befall the black hole may not fall directly, but will have some angular momentum around the black hole which will cause problems to collect into the accretion disk. Quasars can also be switched on or rekindled when normal galaxies join and black holes are infused with fresh material sources. In fact, it has been suggested that quasars can form when the Andromeda Galaxy collides with our own Milky Way galaxy in about 3-5 billion years.
In the 1980s, an integrated model was developed in which quasars are classified as a special type of active galaxy, and consensus appears that in many cases it is only the angle of view that distinguishes them from other active galaxies, such as blazars and radio galaxies.
The mechanism of change in brightness may involve relativistic exposure of an astrophysical jet pointing almost directly at the Earth. The highest known Redshift quota (as of June 2011) is ULAS J1120 0641, with a redshift of 7,085, which corresponds to a distance of about 29 billion light years from Earth (this distance is far greater than the distance that light can travel through 13.8 billion years universe because the space itself has also evolved).
Properties
More than 200,000 quasars are known, mostly from the Sloan Digital Sky Survey. All observed quasar spectra have redshifts between 0.056 and 7.085. Applying Hubble's law to these redshifts, it can be shown that they are between 600 million to 28.85 billion light-years (in terms of the approaching distance). Because of the great distances to the farthest quasars and the limited speed of light, they and the surrounding spaces appear when they exist in the very early universe.
The quasar's power comes from supermassive black holes that are believed to exist in the core of most galaxies. The shift of Doppler stars near the galactic nuclei suggests that they revolve around an incredible mass with a very steep gravity gradient, indicating a black hole.
Although the quasars seem faded when viewed from the Earth, they are seen from a great distance, being the brightest objects in the known universe. The brightest quasar in the sky is 3C 273 in the constellation Virgo. It has an average apparent magnitude of 12.8 (bright enough to be seen through a medium size amateur telescope), but has an absolute magnitude of -26.7. From a distance of about 33 light years, this object will shine in the sky as bright as our sun. The luminosity of this quasar, therefore, is about 4 trillion (4 ÃÆ'â € "10 12 ) times from the Sun, or about 100 times that of the galaxy's giant light like the Milky Way. This assumes quasars radiate energy in all directions, but the active galactic nucleus is believed to radiate exclusively in the direction of its jet. In a universe containing hundreds of billions of galaxies, most of which have an active nucleus of billions of years ago, but only seen today, it is statistically certain that thousands of energy jets should be directed to Earth, some more directly than others. In many cases, the more likely the quasar gets brighter, the more directly its jet is directed to Earth.
Quasar hyperluminous APM 08279 5255, when it was discovered in 1998, gives an absolute magnitude of -32.2. High-resolution imaging with the Hubble Space Telescope and 10m Keck Telescope revealed that the system is gravitantly lit. A study of the gravitational lens of this system indicates that the emitted light has been magnified by a factor of ~ 10. It is still much more luminous than the nearest quasars such as 3C 273.
Quasars are much more common in the early universe than they are today. This discovery by Maarten Schmidt in 1967 is a strong early evidence against Steady State cosmology Fred Hoyle, and supports the cosmology of Big Bang. Quasars show the location where a large black hole grows rapidly (through accretion). These black holes grow a step with the mass of stars in their host galaxy in a way that is not understood today. One idea is the jet, radiation, and wind created by quasars, turning off the formation of new stars in the host galaxy, a process called 'feedback'. The jets that produce strong radio emissions in some quasars in galaxy group centers are known to have sufficient power to prevent hot gases in the groups from cooling down and falling into the center of the galaxy.
Quasars luminosity varies, with time scales ranging from month to hour. This means that quasars generate and radiate their energy from a very small area, since every part of the quasar must come into contact with another part of the time scale to allow for coordination of luminosity variations. This means that quasars that vary on a time scale of several weeks can not be greater than a few light weeks. Emissions of large quantities of electricity from small areas require a much more efficient resource than nuclear fusion that moves stars. Conversion of potential energy of gravity into radiation by infalling into black holes converts between 6% and 32% of mass to energy, compared to 0.7% for mass conversion into energy in stars like our sun. This is the only known process that can produce high strength for a very long period of time. (Stellar explosions such as supernovae and gamma-ray bursts, and the annihilation of antimatter materials can also produce very high output power, but supernovae only last for days, and the universe does not seem to have much antimatter in the relevant amount of time..
Since quasars show all the common properties for other active galaxies such as Seyfert galaxies, emissions from quasars can be easily compared to small active galaxies backed by smaller supermassive black holes. To create luminosity 10 40 Ã, watt (typical brightness of quasars), super-massive black holes must consume materials equivalent to 10 stars per year. The brightest quasar known to devour 1000 solar masses of material every year. The largest known is estimated to consume material equivalent to 600 Earth per minute. The luminosity of quasars may vary over time, depending on the environment. Because it is difficult to fill the quasars for billions of years, once the quasars have finished milling the surrounding gases and dust, they become ordinary galaxies.
Radiation from quasars is partially 'nonhermal' (ie, not due to black body radiation), and about 10 percent are observed to also have jets and lobes like radio galaxies that also carry significant (but poorly understood) amounts of energy in the form of moving particles at relativistic speeds. High energy can be explained by several mechanisms (see Fermi acceleration and centrifugal acceleration mechanism). Quasars can be detected across the observable electromagnetic spectrum including radio, infrared, visible light, ultraviolet, X-rays and even gamma rays. Most quasars are the brightest in their near resting framework of ultraviolet waves from the Lyman-alpha 121.6 nm emission line of hydrogen, but due to the overwhelming redshifts of these sources, that peak luminosity has been observed as far as the red as 900.0m, near the infrared. A small number of quasars show strong radio emissions, generated by the jets of matter moving near the speed of light. When viewed down, these appear as blazars and often have areas that seem to move away from the center faster than the speed of light (superluminal expansion). This is an optical illusion because of the properties of special relativity.
Quasar redshifts are measured from a strong spectral line that dominates their visible and ultraviolet emission spectrum. These lines are brighter than the continuous spectrum. They show Doppler expansion according to an average speed of a few percent of the speed of light. Rapid movement shows very large masses. The hydrogen emission lines (mainly from the Lyman series and the Balmer series), helium, carbon, magnesium, iron and oxygen are the brightest lines. The atoms emitting these lines range from neutral to highly ionized, leaving them highly charged. These various ionisations show that the gas is highly irradiated by quasars, not just heat, and not by stars, which can not produce various ionisations.
Like all active galaxies that are not disguised, quasars can be powerful sources of X-rays. Hard-radio quasars can also produce X-rays and gamma rays by Compton's invers that scatter low-energy photons by radio-transmitting electrons in jets.
Iron quasar shows a strong emission line generated from low ionization iron (FeII), such as IRAS 18508-7815.
The spectral lines, reionization, and early universe
Quasars also gives some clues about the end of Big Bang reionization. The oldest known quasars (redshift = 6) feature the Gunn-Peterson trough and have a recharge area in front of them indicating that the intergalactic medium at the time was neutral. Newer quotas show no absorption area but their spectrum contains a pointed 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.
Quasars show evidence of elements heavier than helium, suggesting that the galaxy undergoes a major phase of star formation, creating a III star population between the time of Big Bang and the first observed quasars. The light from these stars may have been observed in 2005 using NASA's Spitzer Space Telescope, although this observation remains to be confirmed.
Quasar subtype
The taxonomy of quasars includes various subtypes that represent a subset of different quasar populations.
- Radio-hard quasars are quasars with powerful jets that are a powerful source of radio wavelength emissions. It makes up about 10% of the entire population of quasars.
- Quiet radio quasar is a quasar that lacks powerful jets, with relatively weaker radio emissions than the harsh radio population. The majority of quasars (about 90%) are radio-quiet.
- The wide absorption apparatus (BAL) is a quasar whose spectrum shows a broad blue-width absorption line relative to the remaining frame of the quasars, resulting from a gas flowing out of the active nucleus toward the observer. Extensive absorption channels are found in about 10% quasars, and BAL quasars are usually radio-quiet. In the ultraviolet spectrum of the break framework of the BAL quasars, broad absorption lines can be detected from ionized carbon, magnesium, silicon, nitrogen, and other elements.
- Type 2 (or Type II) quasar is a quasar where the accretion disk and the broad emission line are severely obscured by solid gases and dust. They are higher luminosity fellow type 2 Seyfert galaxies.
- Red Quasar is a quasar with optical colors that are redder than ordinary quasars, which are considered as a result of moderate dust extinction levels in a quasar host galaxy. Infrared surveys have shown that red quasars make up the bulk of the total quasar population.
- Optical Variable Query Optimally (OVV) is a hard-radio quasar where jets are directed to the observer. The relativist smile of emission generates a strong and fast quasar variability. OvV quasars are also considered a type of blazar.
- The weak emission line quota is a quasar that has very dim emission lines in the ultraviolet/optical spectrum.
Roles in the cellular reference system
Because quasars are very far, bright, and small in clear size, they are useful reference points in building measurement boxes in the sky. The International Celestial Reference System (ICRS) system is based on hundreds of extra-galactic radio sources, mostly quasars, distributed across the sky. Because they are so remote, they appear to be stationary for our current technology, but their position can be measured with the highest accuracy by very long baseline interferometry (VLBI). The most recognizable position to 0.001 arcsecond or better, which is the order of magnitude more precise than the best optical measurements.
Many quasars
The multi-image quasar is a quasar whose light experiences a gravitational lens, producing a double image, three or four times that of the same quasar. The first gravitational lens to be discovered was a quasar double Q0957 561 (or Twin Quasar) in 1979. The grouping of two or more quasars can be generated from alignment of probabilities, physical closeness, near real physical interaction, or the effects of gravity bending the light of a single quasar into two or more picture.
Since quasars are rare objects, the possibility of three or more separate quasars found near the same location is very low. The first true three quasars were discovered in 2007 by observations at W. M. Keck Observatory Mauna Kea, Hawaii. LBQS 1429-008 (or QQQ J1432-0106) was first observed in 1989 and found as a double quasar; itself a rare occurrence. When astronomers find a third member, they assert that the sources are separate and not the result of the gravitational lens. This triple quasar has a red shift of z = 2.076, which is equivalent to 10.5 billion light years. The components are separated by an estimated 30-50 kpc, which is characteristic of interacting galaxies. An example of a triple quasar formed by lensing is PG1115 08.
In 2013, the second true quasar triplet QQQ J1519 0627 was found with a red shift of 1.51 (about 9 billion light-years) by a team of international astronomers led by Farina of Insubria University, the entire system accommodated by either in 25 (ie, 200 kpc in projected distance). The team accessed data from observations collected at the La Silla Observatory with the New Technology Telescope (NTT) from the European Southern Observatory (ESO) and at the Calar Alto Observatory with a 3.5m telescope from Centro Astronomico Hispano. n (CAHA).
The first quadruple quasar was discovered in 2015.
When two quasars are almost in the same direction as seen from Earth, they appear to be like single quasars but may be separated by the use of telescopes, they are referred to as "double quasars", such as Twin Quasar. These are two different quasars, and not the same quasars as the gravitational lens. This configuration is similar to an optical double star. Two quasars, "quasar pair", may be closely related in space and time, and are gravitational bound each other. This can take the form of two quasars in the same cluster of galaxies. This configuration is similar to the two leading stars in the star cluster. A "binary quasars", may be closely related gravitatively and form a pair of interacting galaxies. This configuration is similar to a binary star system.
See also
- The active galactic core
- Seyfert Galaxy
- List of quasars
References
External links
- 3C 273: Star Stars Varied
- SKY-MAP.ORG SDSS quasar image 3C 273
- Expanding Quasar Out of Image Gallery
- Quasar Spectra Gallery from SDSS
- SDSS Advanced Student Project: Quasars
- Black Hole: Interactive interactive multimedia Web site Gravity Without Stopping Attractive about the physics and astronomy of the black hole of the Space Telescope Science Institute
- Research Sheds New Light on Quasars (SpaceDaily) July 26, 2006
- Audio: Fraser Cain/Pamela L. Gay - Astronomy Cast. Quasars - July 2008
- Merrifield, Michael; Copland, Ed. "z ~ 1.3 - Large unreasonable structures [in the universe]". Sixty Symbols . Brady Haran for the University of Nottingham. Ã,
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