Talk:Quasar/Archive for 2012
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Quasars, most distant
The highest redshift quasar (ULAS J1120+0641, with a redshift of 7.085) is not 29 billion light-years away (which would make it much older thatn the universe) but 12.9 billion light-years away. 149.254.120.140 (talk) 14:09, 9 January 2012 (UTC) paul santon, 12-2-2012
- 29 Gly is correct. See the article on Comoving distance which is linked just after that statement, or look in the archives of this talk page as this has come up many times before. - Parejkoj (talk) 16:42, 9 January 2012 (UTC)
pulsar
maybe their should be a link since people might get confused — Preceding unsigned comment added by Commander v99 (talk • contribs) 19:20, 7 April 2012 (UTC)
- Good point. I have seen people confuse those two before. But how should we link it without suggesting that they are in any way related? - Parejkoj (talk) 14:39, 8 April 2012 (UTC)
How energetic?
"They (...) can emit up to a thousand times the energy output of the Milky Way. (...) The most luminous quasars radiate at a rate that can exceed the output of average galaxies, equivalent to two trillion (2×1012) suns." — Preceding unsigned comment added by 187.4.209.211 (talk) 01:31, 28 May 2012 (UTC)
Lensed quasars
"In 1979 the gravitational lens effect predicted by Einstein's General Theory of Relativity was confirmed observationally for the first time with images of the double quasar 0957+561.[18]" The first confirmation of the gravitational lens effect was by A. Eddington during the 1919 solar eclipse ! M. Tewes (talk) 21:41, 17 September 2012 (UTC)
- This is probably referring to the formation of multiple images of the same source object, rather than deflection of light by gravity. I agree that it's a good idea to clarify that in the text. (Einstein also wasn't the first to predict deflection of starlight; the test measured how much it bent, because relativity predicted a different amount of deflection than Newtonian gravity did.) --Christopher Thomas (talk) 00:29, 18 September 2012 (UTC)
- Yes, the bending of light by the Sun isn't considered an example of a gravitational lens, even though it's the same effect. The gravitational lens article makes the same distinction. Mhardcastle (talk) 06:35, 18 September 2012 (UTC)
Quasars are "one in a million galaxies", from super-large cDs ?
From figure 4.21 of the following webpage:
the space-density of Quasars, converted to number per volume, peaks near (z~2.3), at nearly 40 per cubic giga-light-year, representing nearly one in a million galaxies. Within 1Gly of earth, there are about a hundred large clusters of galaxies, most presumably harboring large central cD galaxies. Ergo, the spatial density of quasars resembles that of large galaxy clusters, and their large central elliptical galaxies. And, Quasars may be generated, by massive mergers, in busy clusters:
Inexpertly, a correlation exists, between clusters & cD galaxies, and Quasars, all of which represent approximately one in a million large galaxies. According to Galaxies & Cosmology by Blanchard, Boisse, Combes, & Mazure (pg. 271), observations show an average of 30 Quasars per square degree of sky, implying more than a million potentially-observable Quasars. And, extrapolating to all-sky, from the Hubble Extreme Deep Field, our visible universe harbors hundreds of billions of large galaxies. So Quasars seemingly represent approximately one in a million galaxies. 66.235.38.214 (talk) 12:34, 19 November 2012 (UTC)
Why is Quasar Motion Across Sky Missing ?
Why is there no mention of Quasar's proper motion; the measured motion of many dozens of these objects across the sky?
Here's a published citation to get you started describing "50-60 sources with observed proper motion with at least 3 sigma significance" presented at the Very Large Baseline Array Conference.
Quasar Apparent Proper Motion Observed by Geodetic VLBI Networks, D. S. MacMillan, NASA Goddard Space Flight Center, Greenbelt, MD, 20771, Future Directions in High Resolution Astronomy: The 10th Anniversary of the VLBA, ASP Conference Series, Vol. 340, 2005, J. D. Romney and M. J. Reid (eds.)
Here's my suggestion to add a sentence : "Some 50-60 Quasars have been observed exhibiting proper motion with at least 3 sigma significance." — Preceding unsigned comment added by DDilworth (talk • contribs) 21:44, 21 November 2012 (UTC)
- As the article you cite says, these apparent motions are very plausibly caused by changes in the source structure, i.e. the structure of the radio jets, not by real motions. (See e.g. Moor et al 2011 AJ 141 178.) So it isn't a particularly interesting or fundamental thing to discuss in the article. Mhardcastle (talk) 08:12, 23 November 2012 (UTC)