What is Quasars: Definition and 60 Discussions

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. 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...
  2. G

    B 83 quasars right up against the Event Horizon

    A few years ago I became intrigued by articles reporting the discovery of stars very close to the purported Big Bang; 400 million years seems an awful short time for a star to evolve. Then more recently the discovery of 2nd generation - hydrogen, carbon stars - in the same proximity, supposedly...
  3. StillLearningToronto

    Using a CCD camera to solve physics problems

    (Sorry for Length) 1. Homework Statement You have decided to use a CCD camera to check if a 16th magnitude quasar is variable. You can presume that all of the light of your quasar falls on one pixel. You know that a star with a magnitude of 0 would deliver 1 × 10^9 photons/second to one pixel...
  4. A

    Calculating the Feeding Rate of Supermassive Black Holes to Power Quasars

    Homework Statement Quasars arise when supermassive black holes swallow nearby gas, or even entire stars. Their masses are typically 10&7 solar masses, and their luminosities are typically around 10&39 W. Hide the children! Roughly how many stars must one of these monsters eat per year, in order...
  5. W

    I Quantum foam ruled out by distant quasars

    In this paper https://arxiv.org/pdf/1108.6005.pdf It is claimed that 'Our results indicate that most of the models of space-time foam consistent with the holographic principle and, consequently, with black hole entropy, can be ruled out for most of the values of the fluctuation amplitude...
  6. V

    B Conflicting thought on quasars and black holes

    After searching elsewhere online I could not find any information about this thought and hope someone may offer some insight. Black holes seem to be generally discussed as having a single entrance point from the event horizon and down into its singularity. I am confused by how quasars have...
  7. 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...
  8. A

    B Just how Powerful is Computer Science + Astrophysics?

    It seems that for a long time astronomy and cosmology have been based on observation and then speculation. Those two tasks are both very hard on their own, with the observation costing tons of money to be able to produce effective telescopes and observation methods. Speculation is even harder...
  9. M

    I Quasars & Redshifts: Measuring Redshifts & Jet Formation

    A Quasar's luminosity is believed to be due to particle jets streaming from it, presumably on the direction of its poles. Reading some of Fred Hoyle's theories (and Halton Arp's) on redshifts, I wondered whether the jets could be forming so close to the "surface" of a black hole that...
  10. wolram

    B What is the significance of the spooky alignment among quasars?

    https://www.sciencedaily.com/releases/2014/11/141119084506.htm Is this alignment spooky or is there some underlying pattern in the universe?
  11. O

    I Unraveling the Mystery: The Composition of Quasars

    So what exactly are quasars made up of?
  12. Miguel de Luis

    B Quasars & Fusion: Could They Generate Energy from Fusion?

    Could quasars be generating energy from fusion? I mean with all that material falling on it...
  13. patellar-myotatic

    A Quantify the mass of polar jets

    I would like a discussion to quantify just how much mass is ejected at the poles (including the mass equivalence of the photons) when jets form. In quasars the black hole presumably reaches over a Billion solar masses, where the mass is proportionate to the mass of the galaxy and is also related...
  14. J

    Astronomy time required to capture exposures problem

    Homework Statement If you have a large telescope that has a 5 meter diameter with a field of view of 1 foot by 1 foot, and a small telescope with a diameter of 1 meter with a field of view of 1 degree by 1 degree, and your trying to take images of 30 quasars that has a limiting visual magnitude...
  15. J

    Do quasars and blazars exist today?

    Do any quasars and blazars still exist today?
  16. ohwilleke

    Experimental Limits on Spin-Foam Effects From Quasars

    Both string theorists and loop quantum gravity theories have proposed that space-time may be something other than the perfectly smooth, perfectly local space of classical general relativity, which can potentially lead to path dependent phase alteration of light from a common source due to the...
  17. J

    Four random quasars in a straight line?

    http://news.nationalgeographic.com/2015/05/150315-quadruple-quasar-mystery-space-astronomy/National Geographic quoting Dr Hennawi, the lead author of the Science paper, says it is a ten million to one chance to find four quasars so close together. How much more unusual is it that in the first...
  18. N

    Schools Graduate School Guidance. I want to be a cosmologist

    I had a lot of trouble in my early undergraduate career and had received some really bad grades. I retook a lot of courses and after 6 years, I am finally graduating with good marks in my third and fourth year courses and I believe I have an overall good understanding of undergraduate physics. I...
  19. T

    Black Holes & Galaxies: How Do They Work Together?

    I have been thinking of how black holes help form galaxies and have come up with this idea. Now I will assume everyone who reads this knows about how black holes and quasars work. Now if you can imagine a quasar in the beginning, ie. Without the galaxy...
  20. R

    Were all galaxies quasars when they were young?

    My understanding is that quasars are galaxies that are billions of light years away. Thus we see them as they were billions of years ago when they were much younger than our own galaxy & other galaxies nearby to us. The immense energy they emit is generated by matter falling into the central...
  21. medgalis

    What Are Quasars & How Do They Work?

    I am really interested what are quasars and how do they work.
  22. SpiderET

    Did Quasars Play a Role in the Formation of Galaxies?

    Im wondering, if there is some theory, which is proposing that galaxies were formed from quasars? Or if not, are there some facts which are opposing such formation?
  23. T

    What speed do quasars eject matter out the galaxy?

    At what speed do quasars eject matter out the galaxy. I heard, I don't if I'm remembering correctly, that quasars can eject matter faster then the speed of light and I am very sure i got this information from the show "the universe" a couple years ago.
  24. P

    Inflation & Quasars energy and 'fast-forward effect' ?

    Having read the 'The bigger bang' book two times over, I am struck by the fact that the author seems to ask and answer the question of quasar energy emission without stating he is doing so or explaining why it would be wrong to assume he is doing so. In the beginning of the book, Lindsey...
  25. A

    Exploring the Possibility of Quasars Emitting Above Their Eddington Limit

    A study is showing that higher redshift quasars emit more and more above their Eddington limit. How is this possible? Shouldnt this be causing the accretion disk to fly apart?
  26. D

    Quasars as indicators of distance?

    I have been doing some thinking about quasars and have been wondering. Are we able to sue the redshift of a quasar to find out the distance of a galaxy? If we know the redshift at a galaxy can't we just use Vrecession= (c*(λ-λo))/(λo), then substitute this value into Vrecession=Hubble's...
  27. A

    Gamma Ray Bursters vs Quasars?

    Okay, so this may be a little bit of a trivial question, but I've read conflicting information and found myself confused as a result. I've read from several sources (wikipedia, books) that GRB's are the most luminous events known to occur in our universe. However, I've also read that...
  28. M

    Can quasars reactivate within an established galaxy?

    Is a quasar a one off phenomenon at the inception of a galaxy, or does a super massive black hole produce quasars repeatedly as a by-product when there is too much matter to be absorbed.
  29. Q

    Does the center of a quasar experience time dilation?

    I recently read that the center of a quasar does not or almost doesn't experience time dilation, can anybody help me understand this more? The text didn't help much.
  30. S

    Quasars with high redshift in nearby galaxies

    http://www.sciencedaily.com/releases/2005/01/050111115201.htm Please see this article. I've been trying to find the thread with 41 questions posted aces days ago. One of the questions was relating to high redshift objects like quasars appearing in near by galaxies. Someonevwanted a reference...
  31. L

    Exploring Quasars and Black Holes

    How a quasar beam can get out of a black hole if no light is suppose to be able to get out of the event horizon of a black hole. ? Is it because the beam is created outside of the event horizon ? From what I understand quasar is created because of excess of matter on the black hole correct me if...
  32. X

    Understanding Quasars & Blazars: Definition & Theory

    Hey guys I am a bit new to the astronomy scene and am trying to learn as much as I can about space and the universe. One thing that has confused me is quasars (and then blazars). Exact definitions of these is hard to find online, pages I've found always just start going into radio waves and how...
  33. F

    How did quasars form with such massive black holes?

    I was reading about quasars, and what I got from it was that quasars are extremely far away (3 billion + light years according to wikipedia), they were common in the early universe, and they have a supermassive black hole in the center of it. My question is how did these quasars get such...
  34. C

    Quasars - how do they emerge from black holes?

    According to everything I've read and heard (as a non-scientist), nothing can come out of a black hole. However, on a couple of documentaries I've seen on the Nat Geo channel in the last week, the astronomers talk about quasars as being massive jets that come out of black holes, because the...
  35. T

    Regarding quasars not showing signs of time dilation.

    Here's the article http://news.discovery.com/space/no-time-dilation-for-distant-quasars.html So the distant quasar is more red-shifted than the closer one, which means the farther one is traveling at a higher velocity, makes sense. My thought is if the quasar is "riding" if you will...
  36. B

    Can someone explain Pulsars and Quasars?

    I know that pulsars are Neutron stars that emit their energy through their poles, bit why do they emit it through their poles, and not their sides? And Quasars, I though that all mater that falls into a black hole never escapes, so how do we see the...''stuff'' leaving it?
  37. P

    Does Time Dilation Explain the Lack of Effects in Quasar Light Curves?

    On a paper published recently by Hawkins (not Hawking): Comments? Opinions? http://www.physorg.com/news190027752.html http://www3.interscience.wiley.com/journal/123345710/abstract?CRETRY=1&SRETRY=0
  38. S

    Quasars: Are We Measuring Them Wrong?

    Why is it that Quasars don't red-shift? Any ideas or speculations? http://www.physorg.com/news190027752.html Surely all the measurements across all these quasars can't all be wrong. Is it possible that the Big Bang theory is wrong? Is it possible that the universe is not expanding? If...
  39. R

    Are Quasars Still Present in Our Universe?

    Do any quasars presently exist in our universe? Or are all the quasars gone?
  40. K

    Seyfert Galaxies & Quasars: Redshift Differences Explained

    I have read on a NASA website amongst other places that "Many astronomers believe that Seyfert galaxies and high-energy quasars are basically the same type of objects, but we are simply viewing them differently". But on the same website it also says that "by measuring their redshifts, we find...
  41. T

    Quasars & Antimatter: Evidence of Abundance?

    We know it is implausible that the local observable universe contains a near-balanced distribution of matter and antimatter because we fail to observe predicted anomalies of high-energy radiation brought about by spontaneous annihilation from matter-antimatter collisions on the borders of such...
  42. O

    How much does dust affect light from high redshift quasars?

    As I understand it, the conclusion that our spatially flat universe is expanding at an accelerating rate is supported by observations of 'standard candles' (type S1a supernovae) which appear less bright than expected when their z exceeds about 0.3 --- . Robert Kirschner has discussed these...
  43. Jonathan Scott

    Quasars: A Different Perspective?

    It seems that there is overwhelming experimental evidence that at least some quasars must have significant intrinsic redshifts (as Arp has been suggesting for years). There is also some evidence from a gravitationally lensed quasar suggesting a significant intrinsic magnetic field. These...
  44. turbo

    SDSS Quasars & Cosmology: Challenges to Current Models

    SDSS is perhaps the most ambitious astronomical survey ever undertaken, and it has provided a wealth of new data. Unfortunately for cosmologists (or fortunately, if cosmologists are willing to re-group), some of the findings are quite inconsistent with their expectations. Scroll down to Nov 2...
  45. A

    How to measure the tangential component of velocity of receding starsor quasars?

    Hi all, How to measure the tangential component of velocity of receding starsor quasars? I ask this because i think the velocity determined by observing the red shift will give only the radial component...won't Thnx for replying...
  46. A

    How to measure the tangential component of velocity of receding starsor quasars?

    Hi all, How to measure the tangential component of velocity of receding starsor quasars? I ask this because the velocity determined by observing the red shift will give only the radial component... Thnx for replying...
  47. A

    What Are Quasars? Explained by Hubble Telescope

    Hi, people, Just to bump myself into the forum could someone address this question about Quasars The Hubble space telescope picks up light from these unimaginably distant energy sources called quasars, which came into being some1 billion years after the big bang or, about some 10/11 billion...
  48. F

    Measuring the temperature of quasars

    Can anyone tell me whether it's possible to measure the temperatures of Quasers from phenomenon such as redshift etc?? As quasers travel with speed comparable to that of light,so does the concept of relativistic temperature come into effect? Are there any research papers available on this?
  49. C

    Supermassive BHs: Forming Farthest Quasars

    I know I am way out of my league but I have a thought experiment concerning BHs and I am trying to fathom super massive BHs with the limited amount of time for them to form to create the farthest Quasars. In my thought experiment I envision a black hole not to be a point but the Planck length in...
  50. G

    How Far Away Are the Farthest Quasars in the Universe?

    I am just a layman who read that the farthest quasars (based on redshift) are about 13 billion light years away. Is that true? I also read that the age of the universe is less than 14 billion years and that the overall shape (from observations of background radiation) is that of a flat...