Talk:Crab Nebula

message: * In response to the edit made by Yao Ziyuan:
SN 1054 was unquestionably the first astronomical object recognized as being connected to a supernova explosion. The statement refers to when the connection was claimed, not when the supernova occurs. Other systems such as SN 185 might have happened earlier, but they were not recognized as being possibly associated with a supernova remnant until quite recently. (And SN 185 is a bad example because it is a controversial association in any case.) Tubbs334 21:17, 27 May 2007 (UTC)
thread_title:  Origins 

message: Is it possible to confirm the dating of SN 1054 by some other studies, not based on dates from Chinese chronicles? For example, a paper by R. Nugent, http://www.journals.uchicago.edu/PASP/journal/issues/v110n749/980055/980055.text.html - together with the sources cited there - suggests the year of 1130 ± 16, rather than 1054, based on linear expansion model. The obvious discrepancy is explained as the effect of the "well-known acceleration in the Crab's expansion", but no estimations are provided. FedorB 21:13, 20 June 2007 (UTC)
thread_title:  Dating 

message: I've chosen the above image as a Portal:Astronomy picture of the week. Since I  can't truthfully claim a neutral point of view with respect to this image, I post here to draw attention for consideration by future editors. – Conrad T. Pino (talk) 03:08, 10 June 2008 (UTC)
thread_title:  Triple Composite NASA Image 

message: I think it is misleading to say that <<Tracing back its expansion consistently yields a date for the creation of the nebula several decades after 1054>>. Rather, the explosion of the supernova took place 6300 years before 1054 A.D., that is at roughly 5300 B.C. (provided that the distance between the supernova and the solar system did not appreciabely change during this time). 141.51.191.59 (talk) 11:30, 30 June 2008 (UTC)
replies: text: *It is common practice in astronomy to date an event by when it was observed from Earth, because distance, and thus how long the light took to reach us, can be very uncertain. --Etacar11 14:59, 30 June 2008 (UTC)
thread_title:  Distance 

message: Hello,
you may want to include this image in the article.
Poppy (talk) 23:58, 28 August 2008 (UTC)
thread_title:  Image 

message: The radius of the nebula reported in the right column once was "6.5 ± 1.5 ly" 
and contradicted the diameter of the nebula reported in the last sentence of 
the first paragraph "the nebula has a diameter of 11 ly (3.4 pc)" which 
gives a radius of 5.5 ly (1.7 pc). Hence, I changed the value in the right column to "5.5 ly (1.7 pc)". Determining the radius of an irregular nebula that isn't all that circular may be unscientific, but this value (5.5 ly) is cited in "An Introduction to Modern 
Astrophysics", Second Edition. By Bradley W. Carroll and Dale A. 
Ostlie, agrees with the 1st paragraph of this same article, and agrees much better with an extrapolation of the radius using its know expansion rate and the date it was observed (July 4th, 1054), including the accelerated expansion since the supernova.
Some Old Man (talk) 12:28, 30 April 2009 (UTC)
thread_title:  Radius of the Nebula 

message: Per this Scientific American article, Arab astronomers did not actually record SN 1054, so I've removed the mentions to them in the "Origins" section. howcheng  {chat} 00:36, 4 July 2011 (UTC)
thread_title:  Arab astronomers 

message: Does this object have a 3C catalogue number. Other similar radio objects do, but this one seems to have it omitted?  — Preceding unsigned comment added by 193.167.170.47 (talk) 19:11, 11 November 2013 (UTC)
thread_title:  3C number 

message: I was disappointed while addressing a citation needed tag to discover that neither of the citations given in the paragraph on Herschel actually supported the content of the paragraph. One was a book review of an offline source and one was linked to a library catalog entry for an article that supported some details in the paragraph but not all of it. I have amended these two references so that they point directly to the sources rather than reviews or catalog entries of them. I think this article would benefit from a more in-depth source review and spot check and the addition of sources where they appear to be lacking. DrKiernan (talk) 15:18, 30 December 2014 (UTC)
thread_title:  Featured article review 

message: Does it make sense to quote a magnitude at 10 parsecs for an object that is over 3 parsecs across?  Especially one calculated by the author of this article from dubious data?  Who says the distance modulus is 11.5?  Has this just been calculated from the distance?  That isn't appropriate as a Crab suffers from non-trivial extinction.  One old source I checked quickly gave a value of 1.6 magnitudes for the visual extinction.  Lithopsian (talk) 22:18, 17 February 2015 (UTC)
replies: text: I believe that for extended sources, the absolute magnitude is computed as though it were emitting all radiation from a point source. NEDS looks to have some current data on foreground galactic extinction. Praemonitus (talk) 21:17, 22 January 2016 (UTC)
thread_title:  Absolute magnitude 

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thread_title:  External links modified 

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thread_title:  External links modified 

message: 184.17.203.207 (talk) 21:33, 23 July 2018 (UTC)
replies: text: Changed to "Researchers". — Huntster (t @ c) 10:57, 24 July 2018 (UTC)
thread_title:  Observers used the Chandra X-ray Observatory to observe 

message: : "At X-ray and gamma ray energies above 30 keV, the Crab Nebula is generally the brightest persistent source in the sky, with measured flux extending to above 10 TeV."
This is a horrible sentence.
So it's brighter than the sun? Is it brighter only in X-ray and gamma ray spectrum? Is it 30 keV in sum or for each X-rays and gamma rays? (Same question with flux.) 91.10.43.221 (talk) 19:19, 4 March 2019 (UTC)
thread_title:  Lede