Talk:Quasar

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[edit] Quasars in the Milky Way Galaxy

Remove entry about quasar being in the Milky Way galactic way. The link cites an ancient paper that claims two quasars with right ascension is the same as the galactic center. Nothing about declination. In any case the galactic center is very well resolved and there is no quasar there. Roadrunner 21:45, 22 Feb 2004 (UTC)

It's not ancient, it's from the seventies, and it states only tiny deviation in right ascension and no observed deviation in declination. That means, in layman's terms, it's in the same place. - Plautus satire 21:56, 22 Feb 2004 (UTC)
If you want I'll cite other papers showing how commonly quasars are determined to be in our galaxy. - Plautus satire 21:57, 22 Feb 2004 (UTC)
A paper written in 1979 is ancient. A paper on quasars in 1995 is old. Things move fast in this field.
Yes, things move fast when divorced from reality. - Plautus satire 02:14, 23 Feb 2004 (UTC)
You can easily look up the coordinates of both 3C345 and NRAO 512 in the NASA Extragalactic Database.....
And what are the coordinates of the "galactic center"? - Plautus satire 02:16, 23 Feb 2004 (UTC)

http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?search_type=Obj_id&objid=337495&objname=1&img_stamp=YES

http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=nrao+512&extend=yes&out_csys=Galactic&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES

They are nowhere near the galactic center. I'm not sure what the web page is trying to say, but to say that quasars have been detected near the galactic center is false. Roadrunner 22:04, 22 Feb 2004 (UTC)
The above discussion is based on error in the use of the term declination. It does not mean radial distance. It is an angular coordinate relative to the celestial equator. Right ascension and declination are 2-d sky coordinates. Two objects with the same such coordinates are along the same line of sight from earth. -- Decumanus 22:08, 22 Feb 2004 (UTC)
Yup. And 3C345 and NRAO 512 aren't even in the same direction as the Galactic center. They have the about the same RA, but the Dec is at least 10 degrees off. Roadrunner 22:15, 22 Feb 2004 (UTC)
FYI. This is the location of the galactic center.....

http://chandra.harvard.edu/photo/2003/0203long/

Interestingly, the quasar you say is not near the galactic center is in that picture. Thank you for finding this image. - Plautus satire 04:38, 23 Feb 2004 (UTC)

Roadrunner 22:19, 22 Feb 2004 (UTC)

[edit] Research sources

If that guy tries to revert this page again, its being protected. -_- WhisperToMe 21:54, 22 Feb 2004 (UTC)

About Plautus. He seems to be well meaning, but he seems to get all his information about astronomy from fringe websites which attempt to argue that mainstream astronomers are blind idiots, who are too stupid to recognize the truth of simple arguments. This gives him a very unbalanced view about what astronomers believe and why they believe it. Roadrunner 22:19, 22 Feb 2004 (UTC)
Attempting to argue mainstream astronomers are blind fools? You mean like Galileo did? Relying on facts is balanced. Relying on fantastical, unprovable notions is not. - Plautus satire 02:12, 23 Feb 2004 (UTC)

Plautus apparently thinks that if a website contains the words "laser star" then it supports his theory. Here's the kind of "laser star" that was being talked about: http://home.erin.utoronto.ca/~jbonham/adaptive_optics.pdf (has wrong date due to resaving.) silsor 22:27, Feb 22, 2004 (UTC)

I apologize for trying to protect this citation. I had posted it based on a summary I wrote of the page over the last year at some point. I've been bookmarking web sites as long as I've been using the internet, so it's impossible for me to be sure my index summaries are 100%, but it's interesting that site is talking about laser guide stars, like the laser guide stars they use at the Starfire beamed energy weapons range in New Mexico, the lab that destroyed the Columbia with their missile defense laser cannon. <- another hotly-contested issue to say the least, it's difficult to get facts into the Columbia entry, let alone "other theories". Apparently the CAIB is given the floor there. - Plautus satire 02:12, 23 Feb 2004 (UTC)
If you want to list the papers that argue that quasars are galactic, be my guest. My prediction is that they are either ancient, or that they come from a rather small number of "usual" suspects, which can be listed.
Something to be aware of
1. There is a publication bias in favor of fringe papers. Any paper that suggests any possibility that quasars are not galactic that isn't totally nonsense will probably get published. Any paper that rebuts it will not. The former is at least original, whereas a paper that punches holes in the argument and reinforces the conventional wisdom has nothing new to offer. For example, you probably won't find a rebuttal to Arp's ideas published recently, because the rebuttals are so well known in the community, that there's no point writing a paper.
A publication bias in favor of fringe paper? Can you demonstrate this bias in some fashion or is that your personal prejudice? - Plautus satire 02:12, 23 Feb 2004 (UTC)
2. The reason I'm a stickler about "naming names" in fringe theories is that once you do, it becomes totally obvious that fringe theories contradict each other as much as they do to standard ideas. For example, Vashini's ideas and Arp's are totally incompatible, and finding quasars within the Milky Way would kill Arp's theories (he argues that quasars are galactic). Sure our current ideas about how the universe works has holes and inconsistencies, but something that you quickly figure out is that the holes and inconsistencies are smaller than alternate ideas. Roadrunner 22:31, 22 Feb 2004 (UTC)

Roadrunner 22:19, 22 Feb 2004 (UTC)

This is dead wrong. Arp said galaxies spawn galaxies. He studied galaxies and he predicted galaxies spawn other galaxies, not that all quasars are galaxies. He also said that galaxies spawn quasars. (sources for these claims: One Hundred Publications of Halton Arp) The other author you tried to mention (Varshni, but then why bother spelling his name correctly, I've been told there is no objective accurate spelling of any proper names in the WTC demolition talk page) states that quasars are stars that lase and presents overwhelming evidence that this is the case. He further identifies no fewer than thirty quasars whose positions have been calculated and which reside within our galaxy, ergo quasars are not all extremely distant. He also cites evidence that "classical" quasar hypotheses make the same predictions based on random noise as they do actual observations (85% identical predictions to those based on random nonsense data) (sources: Laser Star Astrophysics - support for each claim is one or two links from main page in most cases, read it all, you will learn from it- Plautus satire 02:12, 23 Feb 2004 (UTC)

[edit] Proper motion of quasars

Shapiro et al. (1979) have used very-long-baseline interferometry to obtain some evidence on the relative proper motion of two quasars, 3C 345 and NRAO 512. These two quasars are separated by half a degree, and were observed repeatedly with very-long-baseline interferometers over a period of four years. These two sources have approximately the same right ascension as the galactic center. No relative proper motion in declination was detected with the upper bound being under 0.0002 arcsec/yr. this result is fully consistent with our expectations. We note that the measured value gives the relative value of only the declination component of the proper motion, which for one particular pair could even be zero. More such studies would be highly desirable.[1]

The use of the above abstract as a citation here is based on error in the use of the term declination. It does not mean radial distance. It is an angular coordinate relative to the celestial equator. Right ascension and declination are 2-d sky coordinates. Two objects with the same such coordinates are along the same line of sight from earth. -- Decumanus 22:08, 22 Feb 2004 (UTC)
And the quasars in question have approximately the same coordinates as the galactic center. What part of that is so hard to understand? - Plautus satire 04:50, 23 Feb 2004 (UTC)
Read it again: "These two quasars are separated by half a degree, and were observed repeatedly with very-long-baseline interferometers over a period of four years. These two sources have approximately the same right ascension as the galactic center. No relative proper motion in declination was detected with the upper bound being under 0.0002 arcsec/yr. this result is fully consistent with our expectations. We note that the measured value gives the relative value of only the declination component of the proper motion, which for one particular pair could even be zero."
Proper motion in this sense is defined in the two-dimensional celestial plane. -- Decumanus 04:28, 23 Feb 2004 (UTC)
You seem to be redefining proper motion so that it's sole definition is "Decumanus is right." - Plautus satire 04:31, 23 Feb 2004 (UTC)That's right, it does not mean "Decumanus is right," it means the motion on a hypothetically flat plane (the sky). = Plautus satire 04:53, 23 Feb 2004 (UTC)
This is the defintion of proper motion used by astronomers. -- Decumanus 04:33, 23 Feb 2004 (UTC)
The definition of proper motion used by astronomers is "Decumanus is right?" I don't think this is what you meant, can you clarify what you do mean? - Plautus satire 04:42, 23 Feb 2004 (UTC)
As it turns out, we have an article on it. silsor 04:44, Feb 23, 2004 (UTC)

Varshni (1974) has shown that quasar redshift is merely an empty number without physical significance, quasars are stars within the galaxy. However, despite the overwhelming amount of contradictory data, the astronomical community still persists in assuming that the redshift is a valid distance indicator from which they incorrectly deduce that quasars are extra-galactic. The gross overestimation of quasar distance has led to spurious paradoxical properties such as superluminal motion, one of four paradoxes of Kellermann (1972), which we now discuss:[2]

What recent published articles have used Varshni's paper as a reference? -- Decumanus 02:37, 23 Feb 2004 (UTC)
Here is a paper on supersymetry citing Varshni: Solving Schrödinger equation for two dimensional potentials using supersymmetry - This works was part of the communication presented at the VIII International Conference of Symmetry in Physics (1995), Duba/Russia.
Here is a paper on semiconductors citing Varshni The Rate of Radiative Recombination in the Nitride Semiconductors and Alloys - This article was received on Monday, June 3, 1996 and accepted on Monday, December 30, 1996.
Web document citing Varshni on gallium-arsenide, of all things. Is there nothing this man doesn't know? Tpyoed "V.P. Varshni" for "Y.P.", interestingly.
PDF - Design methods of low-voltage curvature-corrected bipolar bandgap ...
I assure you, this man is quite mainstream, and not considered a crank by any but the ignorant. - Plautus satire 03:52, 23 Feb 2004 (UTC)
Varshni citing his own research in his own paper in 1982: PROPER MOTION AND DISTANCES OF QUASARS
Varshni again citing his own research in his own paper in 1983: The quasar PKS 0237-233 - Chance coincidences and the alleged CO redshift systems
Varshni again citing his own research in his own paper in 1988: THE QUASAR Q0051-279 AS A STAR
Varshni collaborating with J. Talbot in 1999: Proper Motion of the quasar Ton 202
You seem to think this man is dead or something. He's still researching and teaching in Ottowa. - Plautus satire 04:20, 23 Feb 2004 (UTC)
What recent particles cite Varshni's paper on quasars as a reference? -- Decumanus 04:14, 23 Feb 2004 (UTC)
Varshni citing his own research in his own paper in 1982: PROPER MOTION AND DISTANCES OF QUASARS
Varshni again citing his own research in his own paper in 1983: The quasar PKS 0237-233 - Chance coincidences and the alleged CO redshift systems
Varshni again citing his own research in his own paper in 1988: THE QUASAR Q0051-279 AS A STAR
Varshni collaborating with J. Talbot in 1999: Proper Motion of the quasar Ton 202
You seem to think this man is dead or something. He's still researching and teaching in Ottowa. - Plautus satire 04:20, 23 Feb 2004 (UTC)
What recent published articles by authors other than Varshni and his students cite Varshni's paper on quasars as a reference? -- Decumanus 04:14, 23 Feb 2004 (UTC)
Are you saying J. Talbot is a student of Varshni? Do you have some evidence to support this claim? - Plautus satire 18:40, 23 Feb 2004 (UTC)

[edit] Varshni's credentials

Yatendra Varshni

EDUCATION: B.Sc. (University of Allahabad, India), M.Sc. (University of Allahabad, India), Ph.D. (University of Allahabad, India)

RESEARCH AREAS: Properties of various types of screened potentials which are used in different areas of physics. Applications of screened potentials in atomic physics. Properties of an expanding plasma with cooling. Population inversion and laser action in such plasmas. X-ray laser. Applications. Quasars.

Yatendra Varshni, Department of Physics, Macdonald Hall, 150 Louis Pasteur, Ottawa, Ontario, Canada, K1N 6N5, PHONE NUMBER: 613-562-5800 ext. 6769, FAX: 613-562-5190 E-MAIL: ypvsj@physics.uottawa.ca [3]

[edit] What is the name of the redshift scale?

What is the name of this scale on which redshift is measured? I haven't been able to find it, only numbers, does it even have a name or is it just "redshift scale"? - Plautus satire 20:16, 25 Feb 2004 (UTC)

Assuming this is a genuine question, I believe the shift is the Doppler effect. It may have something to do with Edwin Hubble also, but as I recall it's primarily associated with Doppler. Jwrosenzweig 20:20, 25 Feb 2004 (UTC)
So it's the Doppler scale? Why isn't this scale named in the entry? If you aren't going to name the scale you have to delete that meaningless, dangling number. (Not you, but anyone, one, people in general.) - Plautus satire

The redshift is simply the difference of observed and rest wavelegth divided by rest wavelength. Thats' it. What causes it depends on the object, so in nearby objects is doppler, but it far away objects is usually cosmological, but some claim in some cases is actually general relativity. So putting "Doppler scale" or something similar would be just plain wrong. Redshift is a number, quasars have redshift between zero and six point something so far. Is a reader doesn't know what redshift is, that is what the links are for. --AstroNomer 04:04, Mar 18, 2004 (UTC)

This whole discussion about quasars is rather slanted for lack of common understanding of basics on part of the two main points of view.

The redshift-distance 'scale' is called Hubble's Law, which is seen most clearly in a 'Hubble Diagram' and is commonly expressed in units of km/s/Mpc (kilometers per second per megaparsec), implying that space is expanding.

The term 'redshift' was never used by Hubble, who actually measured 'radial velocity'. 'Radial velocity' is called a 'redshift' in Big Bang cosmology, because the theory relies on an exclusive Doppler interpretation of radial velocity as evidence of the Big Bang. However this is also a misuse of the term 'redshift', as it is referring specifically to the measure of the expansion of space (in km/s/Mpc) between us and the object, not a measure of actual velocity. Ironically, Hubble himself disagreed with this interpretation:

"Such a condition would imply that we occupy a unique position in the universe, ... But the unwelcome supposition of a favored location must be avoided at all costs ... is intolerable ... moreover, it represents a discrepancy with the theory because the theory postulates homogeneity." ("The Observational Approach to Cosmology", Hubble 1937)

Stated objectively, a measure of 'redshift' means we observe that photons from distant objects in space lose energy as they travel the cosmos (causing a 'redshift' in the wavelength of the photon). Hubble thought that this energy was lost due to means other than the expansion of space as required by the Big Bang, but was never able to find such a mechanism. Today there are several known mechanisms which cause this effect, leaving the cosmological debate wide open. -- Akira-no-Baka (20 Oct 2005)

[edit] Highest redshift quasar

The article says 'which is significant because it implies a maximum distance-more distant quasars should be easily observable if they existed' - is this actually the case and can anyone give a reference for that? The z=6.4 quasar was discovered relatively recently in Sloan. If it had been discovered some time ago then I think you could make a case that any more distant quasars would now have been found, but I'm not convinced you can say that now. EddEdmondson 10:40, 18 Jun 2004 (UTC)

I second the request for references. Please provide links to a few before reverting, as the request has been outstanding for a year.. --Christopher Thomas 16:58, 30 Mar 2005 (UTC)

Hi, I removed the bit about the highest redshift being significant. I'm an astronomer with the SDSS, the survey that formed the basis for finding these high-redshift quasars, and it's not significant. The only reason there is a maximum to the redshift of known quasars is that it's hard to find them using current telescopes and cameras and analysis techniques. The way the current high-redshift quasars are found is by looking for objects that have only been detected in the longest-wavelength 'z' filter of the 5 SDSS filter passbands u, g, r, i, z. Some of the z-band only detections are just image defects, some are cool stars, and a few of them are high-redshift quasars. They do not have any emission at shorter wavelengths because a) the Lyman-alpha emission line is redshifted into the z-band, and it has the shortest wavelength among the strong emission lines that quasars usually have, and b) because absorption by Hydrogen along the line of sight from us to the quasar is eating up flux. To find even higher-redshift quasars, you would need to extend this 'dropout' technique to even longer wavelengths; however, the quasars get fainter at higher redshifts, and the Lyman-alpha line moves to even longer wavelengths, so that you would need to use a camera that is similarly sensitive as the SDSS camera, but observes at longer wavelengths, and can cover a similar area as the SDSS (it plowed through a quarter of the night sky to find 6 quasars at z>6...). Such a camera doesn't exist yet.

So sometimes the reason that nothing is found is not that there's nothing there, but just that the something is hard to spot even if you know it's there. Higher-redshift quasars will be found eventually. More quasars at the same redshift will also be found eventually. Sebastian Jester

I've updated the quasar with the highest known redshift to be CFHQS J2329-0301, z=6.43, discovery published in December 2007. Apetre (talk) 02:42, 8 April 2008 (UTC)

[edit] I'm worried about wikipedia...

This is clearly very OT here... this is the same SDSS guy who wrote the comments about the highest-redshift objects. I checked back to see how the quasar entry had evolved. I want to say that I'm a bit shocked at the incoherence and inaccuracy of the article's content, it certainly has not improved. For example, who cares who thought which quasar was the most luminous if they later turned out to be less luminous? And besides, SDSS has found (or re-found) several quasars that are more luminous than 3C273.

If every wikipedia entry has the same ratio between "what's in the article" and "what an average person who has happened to study the subject matter knows" as the quasar entry, I'm very troubled about how useful the whole thing is. In other words, wikipedia is *a* source of information, but it can never be considered as an authoritative source, because I'll never know whether the latest edit made the entry more accurate, or less.

Of course, I could write a completely new entry that would represent what I think is important about quasars, but if someone else can just edit it back to what it is now, why bother?

Hence, I personally feel it's a waste of my time to contribute anything about quasars to wikipedia because I'd either have to risk that my contribution disappears completely, or have to check back once a week to make sure that nobody has added (obvious or subtle) nonsense. There are more efficient ways to educate the public about your speciality than allowing the public to alter your description of what you know. And there are better ways for the public to learn about quasars than going to wikipedia and hoping that some benevolent person in the know has removed the latest addition of nonsense.

So, please blast me for being off-topic, and off-spirit, but as far as I'm concerned, wikipedia is much ado about nonsense.

Sebastian Jester


Please don't give up on it! Your changes are never lost, but saved in version control and someone discovering a messed-up page can read the previous edition, and you can "revert" it. It would be nice if you did check it once a month (not once a week), but you'll do that anyway when adding new discoveries on the subject, right? You can "watch" the page and have it noted that a change was made, so you don't have to actually keep reading it. That is how quality pages can exist. Długosz
So just checking back on the state of this wiki page... the fact that it's listed as being "controversial" means I just can't change my mind. Controversial amongst whom? The astronomically uneducated half of people who regularly edit this page... Who cares? SJ 22:28, 10 April 2008 (UTC) —Preceding unsigned comment added by 78.42.129.139 (talk)
I don't see anything "controversial" in this page (or any tags to that effect), except the very small (and I'd say, relevant) note in the introduction. I've cleaned up a few of the non-science links at the end. If you have some suggestions on how to make it better, please post them here, or make the changes. It could certainly be improved, but I'd say the article isn't too bad, as far as our current understanding of quasars goes. - Parejkoj (talk) 20:33, 11 April 2008 (UTC)

[edit] Reverting supermassive black hole theory

I reverted this edit by User:Distantbody, which was later reverted by User:Andromachi, but Andromachi's edit was, itself, reverted by User:Raul654, presumably because Adromachi is a banned user/vandal (confused yet?). However, I removed the supermassive black hole explanation as an uncited theory: Distantbody's edit summary suggests some sort of sensationalism without citation of a source. --Deathphoenix 16:51, 13 December 2005 (UTC)

Thanks - you beat me to it. I agree with your reasons. - Avenue 01:33, 14 December 2005 (UTC)
While making a good edit, Distantbody also inserted the theory again. I did some further research and have yet to see the theory mentioned. Quasars and supermassive black holes have been mentioned somewhat (most notably here), but I have yet to see an actual peer-reviewed publication where a group of scientists discuss this theory. Since Wikipedia is not a source of original research, this theory needs to be given a full peer-reviewed document before it can be mentioned here. --Deathphoenix 15:38, 22 December 2005 (UTC)
Google for "active galaxy" and "active galactic nuclei" instead of "quasar" for mechanism papers. See also active galaxy. The edit that was reverted looked redundant, as opposed to factually incorrect - the article already discusses supermassive black holes under "Quasar emission generation". This mechanism is the only plausible one found to date that explains why quasars can vary so quickly (indicating a size of light-hours or smaller), while still producing so much energy. --Christopher Thomas 19:29, 22 December 2005 (UTC)
Thanks for the info. --Deathphoenix 20:21, 22 December 2005 (UTC)


[edit] Request for arguments against gravitational redshift

I have moved the following request by User:70.32.171.199 out of the body of the article.

[OK this is a comment from an anonymous reader. This last sentence makes a lot of sense -- why isn't the redshift due to light escaping a deep gravitational well? -- then the author doesn't go on to pursue this point but instead switches to additional reasons why people don't like the traditional view of what quasars are. Someone please flesh out why in the 60's the idea of the redshift on quasars as being from light escaping a gravitation gradient was rejected. Thanks!]

For context, it came after these sentences:

One great topic of debate during the 1960s was whether quasars were nearby objects or distant objects as implied by their redshift. It was suggested, for example, that the redshift of quasars was not due to the Doppler effect but rather to light escaping a deep gravitational well.

I have also attempted to address their request. -- Avenue 13:51, 26 December 2005 (UTC)

Actualy "frame dragging" is prooved by gravity probe B, Frame dragging ocurse when a massive object rotates, (even around earth) altough the earth doesn't have that much gravity force compared to a rotating blackhole. This might well be just someting close to blackhole the light escapes but redshifted by frame dragging, not that kind of a bad idea

[edit] Can we agree that no one knows what the heck Quasars are?

Honestly, this article is confusing to a layman because it doesn't directly state the obvious. That no one knows what a Quasar is to begin with. The closest explaination, about material being fed into a supermassive black hole is a crock of shit. Lengis 17:06, 12 August 2006 (UTC)

The purpose of Wikipedia's science-related articles is to describe topics as presently understood by the scientific community. While you may feel that the explanation of quasars as being active galactic nuclei is a "crock of shit", most scientists appear to disagree with you. --Christopher Thomas 17:14, 12 August 2006 (UTC)
The problem is, most scientists wouldn't agree actually, because that's not how science works. All scientific theories are taken with a great deal of skepticism, and in this case, the theory stated is a last resort because there are no other credible explainations availible due to our lack of understanding, and technological level. Lengis 18:54, 12 August 2006 (UTC)
I think you missed his point Christopher Thomas. All scientific theories aren't scientific fact, and this article is case in point. The amount of factual evidence that states quasars are galactic nuclei is incredibly soft, being the only explaination currently avalible due to limited understanding. This article states that theory as if it's fact, which shouldn't be done. The fact is, it could be anything. It could be an alien structure created by a level 3 kardashev civilization for all we know. I will change the article to reflect this skepticism. Malamockq 15:15, 18 August 2006 (UTC)
I have a Ph.D. is astrophysics from Caltech, and my thesis concerned the demographics of quasars and other AGN. There is no serious doubt among people working in the field that AGN are caused by supermassive black holes at the centers of galaxies. While all scientific knowledge is subject to revision, there is no particular controversy about this issue at this time, and it doesn't need to be shrouded in caveats. -- Coneslayer 18:33, 18 August 2006 (UTC)
There's no controversy because there are no other explainations possible due to our limited understanding. But the current explaination is weak at best. And the revisions never stated there was controversy, just a general lack of complete understanding. This theory in particular, since the evidence is incredibly light. Ambiguity must be emphasized in this article. We don't know what quasars are, accept it. Malamockq 20:04, 18 August 2006 (UTC)
Provide credible sources showing that the "explanation is weak" and that the "evidence is incredibly light." As I said, I have worked in this field, and have never heard such claims; the standard AGN model is just that--the standard. Your own doubts on the subject are original research and lack verifiability. -- Coneslayer 20:17, 18 August 2006 (UTC)
No, it isn't original research. The fact that I brought up the objection and not Malamockq, should have clued you into that. As for sources, http://evolution-facts.org/Ev-V1/1evlch01d.htm and I quote, "No one knows what they are". Skepticism is valid in this case. Lengis 03:18, 19 August 2006 (UTC)
An anti-evolution web site is not considered a reliable source for scientific information about astrophysics. Peer-reviewed astrophysics journal articles are considered reliable sources for this type of information. --Christopher Thomas 04:27, 19 August 2006 (UTC)
Ah yes, I wasn't aware that was an anti-evolution website. Here's a better source. http://darwin.nap.edu/books/0309033349/html/12.html I will revert the changes you made and cite the new source. Lengis 18:44, 20 August 2006 (UTC)
This reference comes from the early 1980s. As is described in the article, much of the evidence for the current view of quasars was gathered more recently than that. Look at astrophysics publications from the late 1990s onwards. --Christopher Thomas 19:51, 20 August 2006 (UTC)
I'm afraid at this point, you are fillibustering, and already reached a non-inclusive stance, regardless of the evidence I provide. Additionally you have violated the 3 revert rule. Lengis 00:49, 21 August 2006 (UTC)
  • correction*, you WILL violate the 3RR after this, so I'm warning you now. I've provided adequate source material which validates my inclusion. Lengis 00:52, 21 August 2006 (UTC)
I fail to see how insisting on including elements of the last 23 years of research is "filibustering". Furthermore, you appear to misunderstand WP:3RR, which forbids three reversions within a 24-hour period. --Christopher Thomas 01:35, 21 August 2006 (UTC)
Yes, requesting a more recent reference is perfectly reasonable here. And it's actually making more than 3 reversions which is prohibited. -- Avenue 01:52, 21 August 2006 (UTC)
One way of perhaps diffusing this is to change the wording of the first sentence in the last paragraph of the intro to the following:"Though the exact nature of quasars is currently unknown, the current scientific consensus holds that the most plausible explanation is that quasars are powered by accretion of material... [etc.]". My limited understanding of it is that most astrophysicists do believe that this model is (by far) the most plausible. I think that stating that the consensus is that quasars are that, though, oversteps it by half a step. I'm no expert at this but the few times that I've heard professional astrophysicists lecture on quasars to laymen (and undergraduates) they took extra pains to emphasize that their knowledge of them was unconfirmed, in a way that they didn't take those pains when it came to most other things. Just my two cents as someone who just showed up to this dispute. I think the "known to man" addition overstates it much (I don't know who else we would be referring to "known" in this context but man). --Fastfission 03:23, 21 August 2006 (UTC)
I'm not sure it's an overstatement to say that as far as science knows, they are AGNs, as it's not only considered the most plausible explanation - to the best of my knowledge, it's considered the _only_ plausible explanation at present by the vast majority of astrophysicists. If a lurking astrophysicist wants to point me to publications about alternatives that are considered plausible by the majority of the community, I'll happily backtrack on this, but the rapidity of source variation requires quasars to be extremely compact, and the fact that they've been observed to display very strong redshift and, in many cases, have been observed to correlate with optically-visible galaxies makes a pretty strong case. My impression is that any uncertainty is in the precise mechanism of relativistic jet production and the precise nature of black holes, not in the association of quasars with AGNs or the production of jets and associated emissions themselves. --Christopher Thomas 03:35, 21 August 2006 (UTC)
Chris is right. Quasar controversies are over, even though they lasted decades. The only oddballs out still pursuing alternatives are those people angry at the Big Bang. See nonstandard cosmologies for more. --ScienceApologist 06:34, 21 August 2006 (UTC)
I had a science professor who stated quite bluntly that we didn't know what quasars were. He said we knew the effects, and we observed what they emit, but we don't know what they are. Christopher Thomas, it's not so much as there are publications on alternative theories, it's just there isn't sufficient data to conclude indefintely that quasars are just stellar mass being fed into a super massive black hole. Malamockq 17:11, 21 August 2006 (UTC)
I would say that your "science professor" was not particularly knowledgable (or up-to-date) about the field. Once again, by the time I started working on quasars in the late-1990s, there was no dispute within the astronomical community about the link between black holes, AGN, and quasars. Whatever doubt there had been was quashed by the discovery that SMBHs are ubiquitous, even in normal galaxies like the Milky Way. -- Coneslayer 17:19, 21 August 2006 (UTC)
Just because everyone says something doesn't mean it's true. Let's say, that Wikipedia got shutdown. One hundred years later, everyone believes that Wikipedia never existed. Does that mean that Wikipedia didn't exist? No. Wikipedia existed. Same thing with quasars. If everyone thinks they are super massive black holes, does it mean that's how they work? No. Instead of finding the "Correct" answer, we should explain that it is not known for sure how quasars work, and then show the different theories. --Andrew Hampe Talk 01:50, 23 May 2007 (UTC)
Exactly what do you consider "unbalanced" about the Quasar emission generation section? It reads "The best explanation for quasars is that they are powered by supermassive black holes." Do you think there is a better explanation? Do you think that there is even a significant minority of astronomers that think there is a better explanation? What "different theories" do you think we should present here? Please remember, Wikipedia is not in the business of deciding what is correct or not, just of reporting what the current thinking is about a topic. And the goal is not to report every idea that somebody may have, but to present the majority opinion and significant minority opinions in a balanced way. --Art Carlson 08:02, 23 May 2007 (UTC)
To expand on Art's remarks, I wrote a thesis on high-redshift quasars. Most of that work would make no sense if quasars were not powered by accretion onto SMBHs at cosmological distances. My work was carefully reviewed by my thesis committee and the ApJ, and was presented to literally hundreds of astronomers at conferences. Any of these astronomers, if they did not accept the premises listed above, could have asked me about it. Nobody ever did. I have never met a working astronomer (since 1998, when I started grad school) who expressed any doubt about the quasar-AGN-SMBH connection. While all scientific conclusions are subject to revision, the scientific consensus on this topic is extremely strong, and that's what we're supposed to describe. -- Coneslayer 11:49, 23 May 2007 (UTC)
We aren't supposed to describe the scientific consensus. We are supposed to describe the what a quasar is/may be. --Andrew Hampe Talk 15:17, 25 May 2007 (UTC)
Well, if you're going to disregard scientific consensus, then a quasar could be anything. It could be an illusion created by the Flying Spaghetti Monster. Please review WP:SCIENCE. -- Coneslayer 16:24, 25 May 2007 (UTC)
Hold the phone, Andrew! It looks like you don't know the name of the game here. "The threshold for inclusion in Wikipedia is verifiability, not truth." The scientific consensus is verifiable. What you or I thinks a quasar really is, that's "original research". --Art Carlson 16:46, 25 May 2007 (UTC)
I agree with Art Carlson, that we should include only verifiable and objective elements. But IMHO the new introduction written by Andrew Hampe completely fulfills these criteria. Thanks for your contribution. However, Andrew, give it up: you are not the first (and probably not the last) who tries to write a "neutral" description of quasars, and who has his text deleted by one of the talibans censoring this page. These not only refuse to accept a different interpretation of quasars, but they even deny the very existence of controversy. -- Proton
Your opinion is noted but is not supported by the literature as has been carefully documented many times on this talkpage. I have modified the weaseling that was introduced by editors unfamiliar with the subject. "Thought to be" wording is best for articles about speculations not about articles written about observations and testable science. Are we to say that Maxwell's Equations are merely "thought to describe" the behavior of electric and magnetic fields? I think not. Just because there was controversy over the nature of quasars doesn't mean there is any more. Science and the opinion of the scientific community is subject to change. --ScienceApologist 15:42, 28 May 2007 (UTC)

[edit] Quasars are distant AGN

This is taken as basically fact by the astrophysical community. There is no other point up for discussion. No controversy exists anymore. --ScienceApologist 09:08, 19 August 2006 (UTC)

You just destroyed your credibility with that statement. Theories are based on facts, but stating the theory as fact is bad science. Lengis 18:40, 20 August 2006 (UTC)
I don't need any credibility here. You should read-up on scientific theory and fact and get back to us. --ScienceApologist 19:56, 20 August 2006 (UTC)
Lack of credibility makes your statements, and arguments meaningless. Lengis 00:56, 21 August 2006 (UTC)
My "statments" are not the issue. You may wish to read WP:V and WP:CON. --ScienceApologist 01:13, 21 August 2006 (UTC)
No, in this case your statements are the issue because the reflect your credibility. Therefore, I can't take you seriously. Sorry. Lengis 02:42, 21 August 2006 (UTC)
You don't have to "take me seriously". You have just have to discuss and abide by consensus decisions which are decidedly not in your favor at this time. --ScienceApologist 02:45, 21 August 2006 (UTC)
I don't think he's listening to you because you embarrassed yourself by making that statement about theories being absolute facts. Some theories are quite solid, while others pretty soft. This is one of the softer theories. In either case, neither can be stated as fact. Also I don't think a consensus means much. A large consensus also believes the world is a few thousand years old, and was created in 7 days. Malamockq 14:29, 23 August 2006 (UTC)
It might behoove you to read about scientific theory and fact and get back to us. --ScienceApologist 18:29, 23 August 2006 (UTC)


[edit] Quasars effect on Communications

Has anyone got information about how Quasars affect communications here on Earth? —Preceding unsigned comment added by 190.36.210.92 (talk • contribs)

Uh, do you have something in mind? I can't think of any way that they would. Are you thinking of solar flares or something? -- Coneslayer 02:28, 16 October 2006 (UTC)
Positive identification of a previously unknown quasar after hours/days/weeks of sifting through data has been known to have the effect of creating a great deal of communication among scientists. Other than that, since we're talking about some of the distant objects ever studied, there is no effect. siafu 03:42, 16 October 2006 (UTC)

[edit] Current existence of quasars?

The article states that all the quasars that have been found have been very, very far away. Is it safe to assume, then, that all quasars are thus a relic of the early(ish) universe and no longer actively exist? --Jeffrey O. Gustafson - Shazaam! - <*> 09:20, 6 December 2006 (UTC)

"No longer exist" is a term that's hard to justify in a universe where you can see all the way back to the beginning. --ScienceApologist 12:54, 6 December 2006 (UTC)
Eh, yes and no. Although we can see it, something that happened ten billion years ago is not exactly happening now (as far as we know). Its subjective, I guess. In any event, are they a relic of the early universe and what is the earliest quasar we know of? --Jeffrey O. Gustafson - Shazaam! - <*> 21:12, 6 December 2006 (UTC)
The "earliest" quasar we know of is the one with the highest redshift. Since space and time are connected something that happened ten billion years ago "there" is not the same as ten billion years ago "here". --ScienceApologist
Jeffrey, "very, very far away" is a relative term. According to the article, the nearest quasar is 780 million light years away; the age of the Universe is ~13.7 billion years. Thus the nearest known quasar existed when the universe was ~96% of its current age. (There may be some error here if the two numbers I'm quoting assumed different cosmological parameters, but I think the point will stand.) I would say, then, that we have evidence of "recent" quasar activity on cosmological timescales. Why don't we see any closer (more recent) than that? Well, there just isn't that much volume of space at low redshift. If you wanted to prove that there's quasar activity at 99% of the current age of the universe, your survey would be limited to a relatively small distance from the earth, which may not happen to contain a quasar, just because they are fairly rare objects. You can't cover more volume in your survey without also increasing your lookback time. Hope that makes sense. (Note that quasar activity is becoming less common as time goes by, so that's part of the answer. But I don't think it's true that quasar activity is completely eliminated at current times.) -- Coneslayer 22:42, 6 December 2006 (UTC)
The current and accepted model for quasars associates them with the luminous centers of active galaxies. At large distances the luminosity of the quasar, which is on the order of tens to hundreds of galaxies, overpowers the brightness from the rest of its host galaxy (hence why it was considered a 'quasi-stellar' object instead of a galaxy). In general we don't see quasars short of z=.1, however we do see active galaxies, which means that below this redshift we can observe the host galaxy surrounding the AGN. If we can see the host, then the object is no longer classified as a quasar, but as an active galaxy, which is the proposed quasar engine. Essentially, the definition of a quasar limits them to larger distances. --stim 07:45, 15 December 2006 (UTC)

[edit] First paragraph cleanup?

The first paragraph is pretty clunky. Would someone with more background than me like to clean it up a bit? —The preceding unsigned comment was added by 70.110.5.110 (talk) 00:44, 12 January 2007 (UTC).

I agree. As a non-astonomer, I am perplexed by the opening; is a Quasar a type of star? Is it a galaxy? Some other type of object? The stuff about the red shift is doubtless critical, but without a bit more context it's just gibberish. Anchoress 09:04, 3 March 2007 (UTC)
I've taken a stab at fixing it. I've split the old, long introduction into a very short introduction that attempts to answer the reader's first question ("what is a quasar?") in layman's terms, and into a longer "overview" section that provides the background that was in the old introduction.
If this looks ok to enough of the lurkers here, we can remove the "introduction needs to be fixed" tag. Thoughts? --Christopher Thomas 05:46, 14 March 2007 (UTC)
Yeah, that satisfies me, and thank you. My main question about quasars has now been answered! If the tag is still there I'll go remove it. Anchoress 16:07, 14 March 2007 (UTC)

I would like to reopen the discussion about the first paragraph. I am reading it now again after a long while and I think that it is trivial: "A quasar (contraction of QUASi-stellAR radio source) is an astronomical source of electromagnetic energy, including radio waves and visible light." Well, isn't every star and galaxy just that? Basically, every radiating astronomical object is a source of electromagnetic energy, so this introduction says nothing about quasars. We must be more specific. The characterizing property of quasars is their high redshift, therefore I think that this should be mentioned here as a kind of definition. I propose the following: "A quasar (contraction of QUASi-stellAR radio source) is an astronomical source of electromagnetic energy, including radio waves and visible light, whose spectrum shows an unusually high redshift". I think everyone would agree that this is a rather precise and neutral definition. Any comments? Dukeofalba 20:09, 15 May 2007 (UTC)

In the field, currently, Quasars are the superluminous cores of distant AGN. We should be up-front about this. --ScienceApologist 22:29, 15 May 2007 (UTC)
No problem with this interpretation, but we must also be clear about existing controversies. Whether we like it or not, there is an intense debate about quasars (this very discussion is proof of it) which has to be somehow reflected in the article. Writing that "the scientific consensus has been all but settled" sounds dogmatic and is simply not true. You are tacitly admitting it when you say that "In the field, currently, Quasars are...". I agree with you: currently that is the interpretation of the majority, but everyone will agree that the evidence is still not strong enough to settle the case definitively. Further, even if the AGN interpretation is right and even if a consensus has been reached, from a historical perspective a quasar cannot be defined as an AGN (otherwise we would simply call it AGN, and not quasar). A quasar was an unidentified object with certain characteristics which later was identified as an AGN. I will give an example to try and make this point more clear: until the 1920's there was a hot debate about whether nebulae were extragalactic or intragalactic. The case was closed when Hubble proved that many of the nebulae were other galaxies, but it would be wrong to define a nebula as "a galaxy", because in fact *some* nebulae are intragalactic gas clouds. The correct thing is to say that nebulae are "astronomical objects looking like a cloud, which were later identified in most cases as galaxies". The same thing applies to quasars. A quasar is an object with a very high redshift which most scientists think is an AGN. But if we are certain about an object being an AGN we call it AGN; on the other hand, if we use the term quasar we are assuming there is uncertainty.
About the mentioning of the black hole theory, there has been a long discussion in this page about it, which you have simply ignored. Before changing the article, please read first all the discussions to avoid repeating mistakes. Dukeofalba 05:39, 16 May 2007 (UTC)
"will agree that the evidence is still not strong enough to settle the case definitively." --> No, that's truly not the case. Everyone agrees that the issue has been settled definitively especially with the discovery of host galaxies. There has never been a quasar discovered that didn't have a host galaxy. Your historical example also obfuscates. The debate wasn't over nebula in general, but specifically spiral nebulae which indeed are all external galaxies. This is similar to quasars.
The discussion on the page regarding "black hole theory" doesn't address the fact that today that is the only model considered. We have a duty as a mainstream source to report this.
Claiming, as you do, that there are continued controversies is not supported in the literature or by any [{WP:RS|reliable sources]]. Unless you can point us to some that indicate otherwise, I'm going to revert this weasling as POV pushing. --ScienceApologist 11:56, 16 May 2007 (UTC)
You are completely missing the point about the nebula example. Just read my post again. About the lack of debate in the literature: a quick search on Google Scholar for "quasar controversy" returns 189 papers since 2005 alone. I haven't checked all of these papers, because I certainly have more interesting things to do. For this same reason, I am not wasting any more time with you. If you think that the controversy will be over simply by gagging and censoring any discrepant views, that's fine with me. I see the main value of Wikipedia not as a scientific reference tool, but as something that keeps some people busy, who might otherwise go out and maybe harm others who disagree with them. So please, carry on with your Inquisitorial work at Wikipedia, but please never leave your computer. -- Dukeofalba
So you're using Google Scholar to count how many papers happen to have to words "quasar" and "controversy", not bothering to look at them, and on that basis concluding that the AGN nature of quasars is still disputed? If I can get you to go from reading zero papers to reading one paper, why not look at Virginia Trimble's annual update on the state of astronomy? Look at section 10.3 and let me know if it sounds like the quasar-AGN connection is still an open question. I mean, we've found SMBHs in nearly all galaxies, including our own; we see host galaxies of AGN; we can associate the Lya forest of quasar spectra with halos of nearby galaxies... continuing to dispute the AGN nature of quasars is quackery at this point. It's straight out of 1980. -- Coneslayer 19:25, 16 May 2007 (UTC)

[edit] Is the 'introduction context' tag still necessary?

As the editor who placed it, I was satisfied with its removal after improvement of the article. Whoever replaced the tag did not indicate why it was still necessary; could s/he do so? Or was the tag replaced inadvertently? Anchoress 20:32, 7 June 2007 (UTC)

I'm going to remove it because the article seems to provide sufficient context for neophytes now. Thank you for the imprimatur. Antelan talk 20:47, 16 June 2007 (UTC)
I place the tag up there, because there is no tag for "too techinal" for the article page, but it did lack context a little, but yeah, I agree with Antelan, i think the tag should be removed as the intro is decent enough that it's not as big of a priority. (Not trying to imply that there is a secret to do list, just saying there are more important things to do in the article. Not sure what they are though. :) --Andrew Hampe Talk 21:29, 16 June 2007 (UTC)
Thanks all, and Andrew Hampe, forgive me if I'm wrong, but if you think the whole article still lacks context or is too technical, I think there actually is a tag that specific. I can look for it if you like. In fact, I think I actually used it recently. Anchoress 03:59, 17 June 2007 (UTC)
Check the templates in this section. The first is the one you used, but would either of the bottom two be accurate? Anchoress 04:15, 17 June 2007 (UTC)
Are you thinking of something along the lines of {{technical}}? Antelan talk 04:27, 17 June 2007 (UTC)
I don't have an opinion, but if Andrew thinks the article is still lacking in context, perhaps he will find it suitable? Anchoress 05:00, 17 June 2007 (UTC)
I haven't been keeping up with the edit history of the article, was the 'technical' template ever placed? Has there been improvement? Andrew, are you still monitoring this issue? Anchoress 17:30, 27 June 2007 (UTC)

[edit] "sex shit"

Hello. If you find this article by simple search for "quasar" you will see that in the first paragraph instead of "They may readily release energy in levels equal to the output of hundreds of average galaxies combined." => "They may readily release equal levels of sex shit equal to the output of hundreds of average galaxies combined. " This two words "sex shit" need to be removed. I don't know how to do it because in the version to be edited the correct sentence appears! —The preceding unsigned comment was added by 128.255.119.66 (talk) 23:21, 22 February 2007 (UTC).

I've seen this happen a couple of times. I think it's caused by someone else fixing the vandalism after I've seen it, but before I've tried to correct it. Sometimes the vandalism appears to remain in the page regardless - I guess this is due to some sort of cacheing going on. --Random wikipedia user.
To fix it you should probably just purge the page next time it happens to you. You can change the address to have the action set to purge, or you could just make a null edit by editing and saving the page without making changes, which purges the page. (It doesn't come up in the edit history by the way.) --Andrew Hampe Talk 20:51, 16 June 2007 (UTC)

[edit] Quotes

I don't know how to make them, but couldn't there be one of those quote things around Hong-Yee Chiu's quote? Leon math 23:25, 20 February 2007 (UTC)

- Looks like someone fixed it with a quote box. 203.129.142.1 12:05, 12 July 2007 (UTC)GraL

[edit] APM 8279+5255:

Has anyone any answers as to why this very early quasar already has a lot of iron? It seems to be older than the universe itself! —The preceding unsigned comment was added by 165.21.83.247 (talk • contribs) on 08:05, 23 February 2007.

If one wre to look at the 'Galaxy Clock Theory" They would notice a straight line from what would represent the event horizon to the outer most 'ring' of the universe. (If we layed concentric rings over one another it would reach to the outer most ring) notice that a quasar represents the constant of light. On a 2-D plane, the Galaxy Clock would look like concentric rings on paper with only one hand pointed at 12 o'clock. REMEMBER.. see 2-D, think 3-D!! One could measure the distance the visible light would reach out from a quasar by measuring the distance on a 2-D plane from the event horizon to the outer ring of the galaxy. That should equal the radius of the Galaxy. Lets take a look on a sub-atomic level.. One photon of light ocsilating in an orbit once in 1 sec is called 1(Hz). When the photon reaches the starting point again in its orbit, a 'quasar' is emitted from center of the orbit that extends to the outer ring of the atom. We call this quasar on a sub-atomic level a Pulse, or vibration. or Frequency. If it occurs on a micro scale, then it occurs on a macro scale. The milky way Galaxy rotates once about every 225 million years. Consider that ONE OSCILATION. We know on a sub-atomic level a 'quasar' is formed, would it happen on a Macro level as well then? if so, would it negatively impact life in the Galaxy? and would it polorize the entire atmosphere of Earth for the remainder of the Quasar resulting in Aurora Borealis? Could this happen on Dec. 21, 2012? Are our planets going to be in perfect alignment that day? and did anyone else notice that a Quasar's emission would be exactly 90 Degrees to Earths tilt of 23.5 Degrees? ----A non amus. —The preceding unsigned comment was added by 24.4.238.4 (talk • contribs) on 05:14, 14 March 2007.

[edit] Edit conficts

Ok, I'm getting tired of fighting with ScienceApologist on edits for the article, so I'd like to get everyone's opinion on this edit. Which version of this article should be used? Edit Diff The previous edit in this diff, or current edit in the diff? --Andrew Hampe Talk 20:43, 16 June 2007 (UTC)

15-year-olds with little expertise and a seeming lack of desire to do research should not be dictating Wikipedia content. I encourage you to start reading references starting with a selection of astronomy texts. --ScienceApologist 12:00, 17 June 2007 (UTC)
If there are so many references (that are not original research) on quasars, then start adding references to the article. Also, keep my age out of it and don't tell me how much expertise I have. --Andrew Hampe Talk 22:42, 17 June 2007 (UTC)
So why don't you tell us how much experience you have. I've made my background plain throughout this talk page: I've done a Ph.D. thesis at Caltech on the subject of quasar evolution. I've told you that out of hundreds of working astronomers I've met, nobody since I began my career has suggested that quasars are other than AGN at cosmological distances, and that AGN are the result of accretion onto SMBHs. I've pointed out that any such controversy predated the discovery of SMBHs in galaxies including the Milky Way, along with other evidence like Lyman-alpha forest studies relating quasar absorption lines with galaxy halos along the line of sight. I've also referred you to Virginia Trimble's annual round-up of the state of astronomy, wherein you will not find controversy on the points I listed above. You just keep coming back claiming that there's controversy. The ball's in your court. Show that there is still, today, controversy as to the AGN nature of quasars, and that this controversy is widespread enough among professional astronomers to merit inclusion. -- Coneslayer 02:25, 18 June 2007 (UTC)
Only goes to illustrate one of the systemic problems with Wikipedia: amateurs thinking they are experts. --ScienceApologist 12:48, 18 June 2007 (UTC)
ScienceApologist's version. No question. You are, again, claiming controversy where none exists. -- Coneslayer 15:32, 17 June 2007 (UTC)
Agreed. SA's version reads like an encyclopedic article. The other contains phrases like "[...], which nicely explains why there aren't nearby quasars. In this framework, after a quasar finishes eating up gas and dust, it becomes an ordinary galaxy," which doesn't have encyclopedic wording. Antelan talk 22:51, 17 June 2007 (UTC)
I agree completely. Stick with ScienceApologist's version. -- Avenue 03:04, 18 June 2007 (UTC)
Ok, not trying to argue, but i wasn't aware of that line. — Andrew Hampe Talk 22:50, 14 August 2007 (UTC)

[edit] Basic definition (measurementally not interpretationally)

Is there not an agreed upon definition of a quasar such as "a stellar like object with a redshift and an apparent magnitude in the standard Hubble redshift interpretation resulting in an absolute magnitude below some treshold value of minus X". The article as it is now speaks of "high redshifts" or "very high redshifts" but how high is "high" and when does "ordinary redshift" turn into "high redshift"? I guess any star at large distances is a high redshift star but can be differentiated from quasars because of differences in absolute magnitude? After making such a definition one could perhaps make the claim that there is scientific consensus that any object fitting into the definition must be a (as the article says now) "compact halo of matter surrounding the central supermassive black hole of a young galaxy". I guess that people working professionally in the field must have at least a "working definition" of what a quasar is just from the measured redshift and apparent magnitude? Or does the chemical composition differ so much from ordinary stars that a distinction somehow can be made that way? Agge1000 23:56, 14 September 2007 (UTC)Agge1000

QSOs are simply ultraluminous compact objects (and by ultraluminous we mean brighter than most galaxies) that are the cores of young AGN. What makes something a quasar as opposed to an AGN is really just a matter of semantics; for a long time host galaxies couldn't be seen around QSOs. "High redshift" has evolved over the years as well. There was a time when a z=0.5 was considered "high redshift". Today, high redshift is determined in the various contexts. Some people consider z>1 to be high redshift. Others consider z>4. And so on. ScienceApologist 17:30, 16 October 2007 (UTC)
Yes, but how do I know that what I'm looking at in my telescope is a Quasar? At first glance it looks like a star but then one or both of the following holds: 1. When checking the redshift it seems too luminous to be a star. 2.The spectral composition is such as it cannot really be a star. I guess that at large distances you would only be able to identify very luminous galactive nuclei but at short distances a "not so active galactic nuclei" would still appear starlike and have strange spectral characteristics although not be obviously more luminous than a true star. When drawing the conclusion that "More than 100,000 quasars are known", as the article says, there must have been drawn a line somewhere as to what can be identified as a quasar and what can not.Agge1000 20:40, 16 October 2007 (UTC)
You take a spectrum to determine whether it is a star or a quasar. Quasars have incredible emission features and are power-law spectra. In color-color space, there is a selection criterion which preferentially picks out quasars photometrically, but to confirm it you have to get a spectrum. ScienceApologist 21:05, 16 October 2007 (UTC)
As ScienceApologist says, you tell an optical quasar by its spectrum, for example, its strong, broad, high-ionization emission lines (including for example Ly a, C IV, N V). So there's not much point in talking about an absolute magnitude cutoff for distinguishing quasars from stars—if you have a redshift, you have seen the object's spectrum, and they're not at all similar. But sometimes a luminosity cutoff is imposed to separate the optical quasar population from the Seyfert 1 population; often the line is drawn at MB=−23. This criterion isn't universal, though, is not always available (rest-frame B might be outside your spectrum), and it's essentially artificial. -- Coneslayer 13:16, 17 October 2007 (UTC)

[edit] Theories getting mixed up with the Known Facts

I've been doing a bit of research on quasars, and found on the NASA website that one unproven theory is that quasars are nuclei of young galaxies. Therefore the first sentence of this article does not have any proof behind it. Also, there are many more facts on the page that are only theories. I think this page needs serious cleaning up. If anyone disagrees, check out the NASA pages for "Quasars". user:Divya da Animal Lvr

You didn't provide the link you are talking about. Please note that the NASA website is a portal for various subsites, some are not updated anynore since 1996 [4]! Research has been evolved a lot since then. --Patrick1982 07:26, 18 September 2007 (UTC)

[edit] "Young" Galaxies

Question from a Wikipedia newbie: The introductory paragraph mentions that Quasars are found in "young" galaxies, but I'm not certain I know what is meant by "young" here. Are young galaxies ones that existed relatively shortly after the big bang, or is youth rather an initial step in the evolution of a galaxy? Is there some property of older galaxies that prohibit Quasar activity, or does the lack of a Quasar itself mark a galaxy as being old? (I'm guessing that we're saying Quasars were a feature of the universe back when there was more matter available to feed the black holes. If so, it would seem that this is more a property of the early universe as a whole, rather than a property of individual galaxies; I'd think that if even an old galaxy somehow bumped into a sufficiently large cloud of gas, it could generate Quasar-level output while consuming it...) Thanks! Jpietrzak (talk) 00:55, 15 February 2008 (UTC)

[edit] Question

How can we see something 28 billion light years away in a 13.7 billion year old universe? Is there proper motion involved or is this a mistake? —Preceding unsigned comment added by 70.135.192.119 (talk) (transported to the talk page by —Animum (talk) 16:34, 18 February 2008 (UTC))

See these threads from last month in Talk:Universe: 1 2. -- BenRG (talk) 12:50, 20 February 2008 (UTC)

[edit] 28 vs 17.4

I changed the distance to the most distant known quasar from 13 to 28 billion light years, and Fivemack then changed that to 17.4. I admit to knowing nothing about this quasar; all I did was plug the given redshift into Ned Wright's cosmology calculator, click "Flat", and copy the comoving radial distance that it spat out back into the article. Where did the 17.4 Gly figure come from? -- BenRG (talk) 02:06, 21 February 2008 (UTC)

Someone changed it back to 13. I changed it to 28 again pending a response here. I hope this cycle doesn't continue... -- BenRG (talk) 15:54, 25 February 2008 (UTC)

Based on present day theory, the quasar was about 13 billion ly away when it emitted the light we see, it is now about 28 billion ly away due to expansion. So both answers are correct based on what you mean by 'distance away'. Perhaps it could be made a little clearer. PhySusie (talk) 17:47, 25 February 2008 (UTC)

As reasonable as that sounds, it's not correct. Light doesn't really travel at c in cosmology. In terms of straight-line metric distance at a constant cosmological time, the quasar is about 28 billion ly away now and was about (28 billion ly)/(1+z) = 3.8 billion ly away when it emitted the light. There is something called the light-travel-time distance, defined as c times the elapsed time, but it's really just an odd way of stating an elapsed time. I've been replacing LTT distances with present-day metric distances in Wikipedia articles because I think metric distance is the only physically sensible distance measure; it's only with respect to the metric distance that the universe is homogeneous and Hubble's law holds. The metric distance at the time of light emission makes some physical sense, but it doesn't always increase with increasing redshift. The CMBR is only around 40 million light years away by that metric, when really it should be farther than everything else we see. -- BenRG (talk) 00:00, 26 February 2008 (UTC)

Shouldn't the article mention that we kind of have a problem when we find something that is 28 billion ly away in a universe that is estimated to be only about 13.7 billion ly old? Isn't this a current problem in cosmology? --KarlFrei (talk) 11:56, 4 March 2008 (UTC)

No. There is no "problem" with cosmology here. The issue is simply that the question "how far away is light emitter X" doesn't have a single, simple answer when the distance to X has changed substantially between the time the light left X and the time you detected it. See Distance measures (cosmology) for possible interpretations of "distance"; note the plot at the bottom, and see that some measures can be larger than lookback time. By analogy, consider an ant walking at constant speed on a rubber band, which is being continuously stretched. By the time he gets from one end to the other, the length of the rubber band will be greater than the distance that the ant walked (basically, because some of the expansion took place behind him). -- Coneslayer (talk) 20:25, 4 March 2008 (UTC)
See also Observable_universe#Misconceptions, specifically the "13.7 billion years" bullet. -- Coneslayer (talk) 20:53, 4 March 2008 (UTC)
Thank you for your explanation. So perhaps we could add a line to the article saying that this does not contradict the estimated age of the universe, with a link to those misconceptions? I am sure I am not the only one who thought this (I hope). --KarlFrei (talk) 09:48, 5 March 2008 (UTC)
Oops, this has already been done. Never mind! --KarlFrei (talk) 13:38, 5 March 2008 (UTC)

[edit] Impossible Distance Cited

When astronomers speak of distances to objects in the universe they speak of them in terms of the age of the light that they are receiving. The Universe being only approximately 14 billion years old, could not have observable objects with light 28 billion years old. —Preceding unsigned comment added by Quidproquo2004 (talk • contribs) 04:54, 2 April 2008 (UTC)

Actually, the distance across the universe is on the order of 90billion light years. In the case of the big bang, the universe was (maybe still is?) expanding faster than the speed of light. Physicists now say that it's ok for something to recede faster than light, but approaching FTL is still forbidden.--MaizeAndBlue86 (talk) 11:29, 2 April 2008 (UTC)

Please see KarlFrei's question immediately above yours. It's essentially the same concern. -- Coneslayer (talk) 12:56, 2 April 2008 (UTC)

(You could also see the question immediately above that one, which is also essentially the same. Groundhog Day was two months ago, but you wouldn't know it here...) -- Coneslayer (talk) 13:01, 2 April 2008 (UTC)

It's a bit scary how many people have been visibly confused by this change to the article. For every reader who edits the article or posts a question here there must be dozens or hundreds who have the same reaction but don't make an edit to show it. Someone also asked about it at the reference desk, spawning this discussion, for which I actually drew a 3D visual aid, reproduced to the right. The brown line is the earth, the yellow line is the quasar, the orange line is the distance to the quasar right now (28 billion light years), and the red line is the path of the light from the quasar to us. The grid lines mark off billions of years and billions of comoving light years. The red line "moves at the speed of light", meaning that it always makes a 45-degree angle with the local grid lines. The way that space seems to curve around into a circle is an artifact of the embedding with no physical significance, and I trimmed it short of a full circle to emphasize that. The pictures are numerically accurate (I calculated the shape from the WMAP data) and you can verify by visual inspection that all of the distances and times come out right. I think these diagrams and the explanation are far too much of a digression for this article, but maybe they'll help someone here on the talk page. -- BenRG (talk) 10:18, 16 April 2008 (UTC)