Quasar Definition and 61 Threads

A quasar (; also known as a quasi-stellar object, abbreviated QSO) is an extremely luminous active galactic nucleus (AGN), in which a supermassive black hole with mass ranging from millions to billions of times the mass of the Sun is surrounded by a gaseous accretion disk. As gas in the disk falls towards the black hole, energy is released in the form of electromagnetic radiation, which can be observed across the electromagnetic spectrum. 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. Usually, quasars are categorized as a subclass of the more general category of AGN. 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 1950s 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. As with other categories of AGN, the observed properties of a quasar depend on many factors, including the mass of the black hole, the rate of gas accretion, the orientation of the accretion disk relative to the observer, the presence or absence of a jet, and the degree of obscuration by gas and dust within the host galaxy.
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.More than a million quasars have been found. The nearest known quasar is about 600 million light-years away (Markarian 231).
The record for the most distant known quasar keeps changing. In 2017, the quasar ULAS J1342+0928 was detected at redshift z = 7.54. Light observed from this 800 million solar mass quasar was emitted when the universe was only 690 million years old. In 2020, the quasar Pōniuāʻena was detected from a time only 700 million years after the Big Bang, and with an estimated mass of 1.5 billion times the mass of our Sun. In early 2021, the quasar J0313-1806, with a 1.6 billion solar-mass black hole, was reported at z = 7.64, 670 million years after the Big Bang. In March 2021, PSO J172.3556+18.7734 was detected and has since been called the most distant known radio-loud quasar discovered.

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  1. H

    I "Quasar clocks" and time running slower long ago

    Regarding the new "quasar clock" data showing that time ran more slowly (~5-fold) shortly after the Big Bang: is it all based on the periodic variation in luminosity at various wavelengths of some quasars (and presumably explained by the special relativistic time dilation effect from "spatial...
  2. S

    I Conservation of energy in quasar outflows?

    I found this article* about the behavior of quasar outflows in cosmology and how they can create a magnetic field. In section 2.1.4., the authors say that when a quasar produces a "wave" or an outflow, the material will be emitted with energy coming from both the quasar itself and the Hubble...
  3. Robert Friz

    I What Mechanism Creates the Jet Emanating From a Quasar?

    Given that a quasar is a super massive black hole with an accretion disk rotating at some significant percentage of the speed of light, what is the mechanism that generates the enormously luminous jet that emanates from the "poles" of the black hole that has become a quasar? a. The magnetic...
  4. C

    I What powers the quasar magnetic beams that power jets?

    I am reading up on quasars because I am interested in the magnetic beams that emanate from their poles, accelerating material. I read that the magnetic beams are generated by the orbiting debris the quasar is consuming. Sorry, that doesn't sound right to me. I assumed the black hole core is...
  5. C

    I Material source of the quasar redshift

    When I see discussions about quasar redshift, exactly what are they talking about? I assume a quasar is similar to a black hole, so emits little radiation from the main mass. The light from a quasar comes principally from its jets of accelerated material, no? Which means the jet pointed...
  6. S

    B We see a quasar 13 billion light years away. What does this mean?

    Summary: If the furthest quasars we can see are let's say 13 billion light years away from us, then does this mean that the distance between us and that quasar was 13 billion light years at 13 billion years ago? To anyone educated in physics this might be a silly question but to me this is...
  7. S

    I Would we know if the Milky Way were a quasar?

    AIUI, a quasar is simply a black hole at the core of a galaxy that shoots out an enormous amount of energy along the axis of circulation. Since we are far from that axis, we cannot look into the Milky Way's core from that vantage point.
  8. FelixLudi

    I Possibility of a quasar jet laser impacting Earth directly

    I understand quasars as black holes with an accretion disk and occassional jets of mass being shot out of the black hole from it's top and bottom. (Correct me if I'm wrong) If so, what is the actual possibility for that type of quasar to be rotated so heavily that it rotates on a horizontal...
  9. StillLearningToronto

    Calculating Quasar Variability Using CCD Camera and Magnitude Comparison

    Homework Statement You have decided to use a CCD camera to check if a 16th magnitude quasar is variable. With your telescope/camera combination, you know that a star with a magnitude of 0 would deliver 1 × 109 photons/second to one pixel, so this allows you to work out the photons/second from...
  10. E

    I Understanding the Ly-α Forest for EnSlavingBlair

    Hi, I'm currently trying to wrap my head around how the Ly-α forest works. This is what I have so far; A distant quasar produces these Ly-α photons, which occur when a hydrogen's electron drops from n=2 to n=1, and has a wavelength of around 121nm (depending on the exact transition). This...
  11. quasarLie

    A Does a Quasar Have Proper Motion?

    Hello, Does quasars has a proper motion? I searched in different article and sometimes they are considered as objects having a proper motion and other times not. So I want some clarification. in which case can we say that a quasar has a proper motion? Thanks
  12. quasarLie

    B Exploring Quasar Spectral Energy Distribution

    Hello, What do you think about this article? https://arxiv.org/abs/1502.05850 Why and how do we mesure the Spectral Energy Distribution for quasars? Thanks
  13. S

    A New high-redshift quasar age issue

    Does the new quasar http://news.bbc.co.uk/2/hi/science/nature/649059.stm indicate a challenge for models of quasars? Some of the ritz-type models do provide explanations for these, e.g., http://faculty.washington.edu/devasia/Physics/Devasia_cosmology.pdf It provides potential explanations to...
  14. A

    I Quasar Number Densities and Lifetimes

    From deep galaxy counts, it is estimated that there are about 40 billion galaxies in the observable universe (not including probable multitudes of dwarf galaxies too faint to observe). Assuming that the mean age of these galaxies is 10 Gyr, and that each one goes through an AGN episode once...
  15. S

    I The error bars of redshift drift

    Dear all, I am reading the paper "Cosmic dynamics in the era of Extremely Large Telescopes " by Liske et al. about redshift. I get the physical meaning of redshift drift, but when it comes to the error bars, I am confused. - Aren't the error bars given in equation (15) ? - Isn't this function...
  16. A

    A Lyman-alpha forest: why not Lyman-beta?

    Hello everyone! We observe the so-called Lyman-alpha forest in the spectrum of distant quasars and it is said that these multiple absorption lines are due to the presence of intergalactic HI clouds that absorb light at the wavelenght of 1216 A , the Lyman-alpha transition. My question is the...
  17. A

    I Quasars: What Metric Should You Use?

    Hello I just got interested into quasars and I have a question:What metric do you use for quasars?
  18. P

    I Quasar Brightness: A Case of Light-Days or Light-Years?

    The video: When Astrophysicists detected Quasars, they thought that they could not be more than a few light-days across as they were changing their brightness in just a few days. If we assume that they are light-years long, then the change in brightness from the other side would be observed...
  19. J

    What is the Concept of Singularity in Relation to Black Holes?

    I'm looking for help in understanding the meaning, nature and/or concept of singularity as such applies to the mechanics of a black hole ...
  20. M

    Solving Gravitational Lensing Homework for Hubble Constant

    Homework Statement A quasar at redshift 0.3 is gravitationally lensed into two images by an elliptical galaxy at redshift 0.18. The two images of the quasar are separated from the center of the galaxy by 1.1 and 1.6 arcseconds, on opposite sides. One of the quasar images flares up in intensity...
  21. S

    The 'Huge-LQG' quasar 'structure' does not violate homogeneity

    There was some excitement a few months ago about the discovery of the Huge-LQG quasar structure, claimed to be the "largest structure in the Universe", which was said to violate the cosmological principle and the assumption of homogeneity of the Universe. Some previous threads on this topic on...
  22. A

    Quasar is a huge source of energy

    I know that the quasar is a huge source of energy, it can produce energy and light more that glaxies do ; so the question is how that can be possible and the quasar is a super massive Black hole which absorb every thing even Light couldn't escape ?! My Friend tell me when the Black Hole is...
  23. J

    What is the Connection Between Quasars and Black Holes?

    Ive looked on a good number of websites, including the pedia, and i still feel like i didnt get a straight answer. What exactly is a quasar. Is it a black hole in the center of a galaxy? What is the physical makeup of a quasar?
  24. Astronuc

    Largest Structure in Universe: 4B Light-Years Long LQG

    Largest Structure in Universe Discovered http://news.yahoo.com/largest-structure-universe-discovered-093416167.html "An international team led by academics from the University of Central Lancashire (UCLan) has found the largest known structure in the universe. The team, led by Dr Roger...
  25. B

    Quasar Mass-Luminosity, High Mass Turnoff Evolution and a Synchronization Puzzle

    Quasar Mass-Luminosity High Mass Turnoff Evolution and a Synchronization Puzzle It is unusual that a generation of researchers has the opportunity to completely rewrite, to replace major established scientific theories. The observation that quasars are turning on and off, at a specific mass...
  26. B

    Quasar Turn On z<1 Quasar Clustering

    Based on assumptions concerning the quasar mechanism it was assumed that quasars are turned on due to mergers. Observationally for z<1 where it is possible to determine if the quasar's associated galaxy is or is not merging it has been found that the quasar turn on does not correlate with...
  27. I

    Is a black hole a quasar or blazar?

    Hi, Is Sagittarius A* the black hole a quasar or a blazar? As far as I've understood, AGNs are quasars, blazars or seyfert galaxies. Can someone please explain how the shockwaves/knots in the jets emitted by black holes can be detected?? Thanks :)
  28. M

    Can quasar gets converted into pulsar?

    Quasars are galaxies which are very active at centre pulsars are dense stars... Since pulsars rotate very fast it can be a quasar gone crazy?
  29. I

    How to Calculate the Length of a Quasar Jet?

    Hi there, I have got a real quick question. From where am I supposed to calculate the length of the jet ? http://i42.tinypic.com/w72929.jpg
  30. D

    Hard evidence for quasar lensing

    Hello, could someone point out to me 1) Ironclad evidence of correlated light curves - and I mean a correlation that is beyond doubt - among lensed quasars 2) Morphological correspondence - e.g. corresponding jets - in images of lensed quasars. I can find sketchy cases which may be...
  31. Dotini

    Most Distant Quasar a Theory Problem?

    http://www.physorg.com/news/2011-06-astronomers-universe-distant-quasar.html The quasar that has just been found, named ULAS J1120+0641, is seen as it was only 770 million years after the Big Bang (redshift 7.1). It took 12.9 billion years for its light to reach us. These observations...
  32. TrickyDicky

    Cosmological principle and quasar distribution

    Our cosmology model follows the cosmological principle according to which we are not in a privileged place in the universe and there is homogeneity, but if you take a look at the distribution of quasars in the universe there seems to be a "quasar spherical void" roughly one billion lightyears...
  33. QuarkCharmer

    Real Quasar Image: Gamma Radiation Burst on Science Channel Program

    I saw a real image of a quasar bursting out gamma radiation on a science channel program and I am having trouble finding the image, or any like it on the internet. All I can find are CG rendered things, and IR/UV images. The photo that I am referring to looked a bit like the Hubble deep field...
  34. Drakkith

    What is the difference between the left and right pictures of a Quasar Core?

    So I was looking some stuff up on Quasars on Wikipedia and noticed this picture. http://upload.wikimedia.org/wikipedia/commons/a/ab/2003-03-b-web.jpg It says that this is a Quasar Core. What exactly is the difference between the left and right pictures here? Did they block out the light...
  35. K

    Quasar Alignment to Cosmic Strings

    A very interesting but speculative paper was published in the Physical Review and arXiv recently about the possibility of the former existence of Cosmic Strings at the point of Electroweak energies. Robert Poltis and Dejan Stojkovic http://prl.aps.org/abstract/PRL/v105/i16/e161301...
  36. S

    Find speed of quasar from observed and actual wavelength readings

    1. Astronomers on Earth observe a feature at 442 nm in the spectrum of a distant quasar. However, it is known that this feature corresponds to 581 nm in the rest frame of the quasar. Calculate the speed of the quasar. Enter your answer as a fraction of the speed of light, positive if the quasar...
  37. U

    What does light emitted by quasar convey?

    people say that light emitted by quasar states that it is moving away from us? why? is it related to doppler effect? if so please explain.
  38. S

    Anomalous Quasar Observations 200k Light Year Jet? And So On.

    If Astronomers stated that they had using the Hubble telescope found a remote island on the Earth with 1000 meter tall Homo sapiens we would based on scientific knowledge and logic concerning the biological limits of animal structure (any land based animal that moves on the surface of the earth)...
  39. S

    Explaining Quasar Feedback for the Struggling

    can anyone explain quasar feedback.. having some trouble.
  40. P

    What's the most distant observed star which is not a supernova or quasar?

    I hear that large telescopes can resolve the Andromeda galaxy into individual stars. Is it possible to do the same for galaxies outside our local group? Also, have we observed any stars which sit in deep inter-galactic space, far from any galaxies?
  41. C

    Comparing Quasar Varying Timescales to Black Hole S Radius

    Homework Statement If a quasar varies on a time scale of four months, how does the maximum size of the emitting region compare with the Schwarzschild radius for a 109 MSun black hole? Homework Equations The Attempt at a Solution Calculating the S radius of the black hole is...
  42. T

    A non-technical explanation for FTL quasar motions

    A non-technical explanation for "FTL" quasar motions I was trying to think of an accurate but non-technical explanation for quasar motions that seem to be faster than light, and I came up with one. A have a friend in Atlanta and he sends me a book via UPS. That book takes three days to get...
  43. N

    Recent research relevant to quasar evolution

    The https://www.physicsforums.com/showthread.php?t=282116" in the Cosmology section kicks off with a reference to a late 2005 Space Telescope Science Institute (STScI) conference presentation on some recent research results on high-z quasars, from the SDSS. Much of the discussion in that...
  44. marcus

    Observing Quasar Accretion Disks: Scientists See Standard Cosmology at Work

    Nice picture of quasar accretion disk---pat on back for standard cosmology in Nature The 24 July issue of Nature reports some beautiful observational work, using a polarized light filter. Actually able to SEE the hot blue accretion disk whirling around a supermassive black hole at the center of...
  45. Jorrie

    Cause of Quasar Wind: The Mystery

    I've scanned some literature, but could not find a description of the mechanism that causes the "thin vertical wind"* from the accretion disk of a quasar. Can someone please explain or point me to an accessible paper? *Elvis M., 2000, Astrophysical Journal 545, 63
  46. T

    Gravitational Redshift Contribution to Quasar Redshift: Explaining Hubbles Law

    Does anyone know how much percentage of the total redshift of a quasar is contributed by Gravitational redshift considering light from the Quasar is emitted by heavy active galactic nuclei ? If there is a significant contribution from gravitational redshift then how will the Hubbles law hold...
  47. T

    Exploring Quasar Energy Theories

    What are the available theories to explain the amount of energy concentrated in quasars? And what are possible problems in those theories? I don't have any background in this, I'm just trying to ascertain whether the philosophy of technology book I'm reading is still up to date. Thanks.
  48. B

    Double Lobed Radio Galaxies &amp; Seyfert Galaxies: Similar Energy Sources?

    What would be some arguments that show that double lobed radio galaxies and seyfert galaxies have similar energy sources? I mean i know they are powered by black holes right? are there energy arguments i can make though? thanks
  49. N

    Is the Quasar in NGC 7319 Really Inside the Galaxy?

    [Moderator note: this thread has been created by splitting out posts related to 'the quasar "in" NGC 7319', in the https://www.physicsforums.com/showthread.php?t=113862".] Ah, the quasar that shines through a 'hole' in a galaxy! Those galaxies, they sure look 'solid', don't they? Who'd'a...
  50. Chronos

    Quasar Anomalies: Lack of Time Dilation in Variability

    I am very disturbed by the lack of time dilation in the variability of quasar v redshift studies. http://www.arxiv.org/abs/astro-ph/0105073 Title: Time Dilation and Quasar Variability Authors: M.R.S. Hawkins The timescale of quasar variability is widely expected to show the effects of time...
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