Talk:Crab Nebula

Origins

 * 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)

Dating
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) There is a possibility that is was recorded by irish monks in one of the numerous irish annals. I am a bit dubious as to the validity of the annal as it lists a star visible during the day for one day on april 24 1054, sometime before the Chinese accounts were made. And supernovae do not release a flash that would be required for both accounts to be reconciled. — Preceding unsigned comment added by 86.43.94.254 (talk) 12:12, 30 August 2011 (UTC)

Triple Composite NASA Image
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)

Distance
I think it is misleading to say that <>. 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)
 * 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)

Image
Hello,

you may want to include this image in the article.



Poppy (talk) 23:58, 28 August 2008 (UTC)

A 3-D animated GIF may be helpful, like this one: http://www.flickr.com/photos/hindt3d/2141719273/ —Preceding unsigned comment added by 192.154.91.225 (talk) 20:17, 4 March 2010 (UTC)

Radius of the Nebula
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)

Arab astronomers
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)

Apparently they were added back. As the SN 1054 article makes clear, which is really the appropriate place to discuss this in any detail, SN 1054 was "recorded by Chinese astronomers in 1054". Mentions of Japanese or Islamic astronomers would be more tenuous. Apparently there is one record by an Islamic astronomer, who lived in the 13th century, and one by a Japanese astronomer, who also lived in the 13th century. So it may be argued (i.e., over at SN 1054) that the event did not go entirely unrecorded in both Japan and the Islamic world, but it would be wrong (or unsubstantiated) to say that it was "recorded by astronomers in 1054" in those places. --dab (𒁳) 20:31, 14 April 2013 (UTC)

3C number
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)

Featured article review
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)

Absolute magnitude
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)
 * 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)

Crab nebula / PWN
This edit is quite wrong. It is a common misnomer. After just re-reading many articles on Pulsar wind nebula, the Crab nebula is a Supernova remnant (SNR) (3.4pc.). The Pulse wind nebula is the inner part of the Crab (<1 pc.) closer to the pulsar, being separate from the expanding wavefront. (It is interesting that the image of the PWN appears under the Crab pulsar section.) This is explained in this image here And the Chandra image is discussed here. .

The reason why they are separated is to avoid confusion, with the PWN associated with the pulsar (where the X-ray ring defines the end of the PWN, whose particles move close to the speed of light) and the Crab nebula associated with the SNR (where, inside it is the expanding nebulae is moving 70,000 1,500 km.s-1.] It is separated by the wind termination shock, where outside it is the non-thermal nebula. This is explained in the pdf by  K. Valerius here.


 * The PWN is catalogued as PWN J0534+2200
 * The Crab Nebula SNR is SNR 184.6-5.8

This appears here.

I have just rewritten the Pulsar wind nebula, and have made sure the definitions are clear and precise.

I have reverted your edit again, but I have left the same statement at the end of the Introduction. This avoids the first sentence which just confuses the reader. I have intended to add another section on the Crab nebula, specifically on the Crab's PWN.

I accept your position, and formal suggest we get consensus on this. Arianewiki1 (talk) 08:16, 27 March 2017 (UTC)


 * I have written some compromising text at the end of the Introduction here whilst we seek consensus. The main issue is why they are included together sometimes, because it depends on the evolutionary status of the pulsar, which changes as the SNR evolves. It is not simple to explain it, which I've attempted to do in the Pulsar wind nebula article. Personally, I don't think it matter where the text lies, but adding it in the first sentence leads only to confuse the reader - especially as differentiation is highly technical.
 * I'd suggest leave the structure as it is now, and we can sort out the ins and outs in the Talkpage. Thanks. Arianewiki1 (talk) 09:03, 27 March 2017 (UTC)


 * , I'd like to clarify the designation of the PWR if possible. It is not classified as "PWN J0534+2200" as far as I can tell...this designation exists literally no where that I can find. That designation is for "PSR J0534+2200". This table is the only resource I've found where the PWN is even vaguely given a designation, "SNR/PWN G184.6-5.8", and even then it is lumped together with the SNR. I fully accept that the SNR and PWN are two very different phenomena; my argument is that they are not, in any significant way, designated separately, and that the term "Crab Nebula" applies to both. There are plenty of sources which support that idea. — Huntster (t @ c) 13:40, 27 March 2017 (UTC)


 * Try this here. Dictionary of Nomenclature Example  However, it is not typically unified, because there are only two dozen examples. Pulsar Wind Nebulae - as the names says they are associated with pulsars. I.e. Mostly because you can have PWN without a SNR (relic nebula)
 * The reason they are sometimes lumped together is because of the age of the Crab nebula, because (simply) because of the boundary between wind termination shock (in a shell) and the interstellar medium. See K. Valerius p.2 here." The Crab lies between the two.
 * If you want to link the two. Fine. However, it has to be explained in the article, which it is not. Anyone reading it first off is left confused. As for the SAO link, you are making an assumption on a caption, which shows an image of the SNR calls it a pulsar wind nebula, when the text says "... .form a nebula around the pulsar: a pulsar wind nebula." You can't see the PWN! Hence the utter confusion. Extraordinarily, it is based on the article on PSR B0355+54 and not the Crab Nebula. (I question the source, here, actually.)
 * I think the question is where to put this text not getting caught in its nuances! (I need more time to think about this.) Arianewiki1 (talk)


 * , I'm actually pretty satisfied with the article wording as it stands, except that the unsourced sentence at the end of the new material needs fixing. Regarding SAO, they also specifically say in their article "The most famous example of a pulsar wind nebula is the beautiful and dramatic Crab Nebula", but as I said, I like the wording in our article. It briefly explains what's going on, that there are relational questions, and why. — Huntster (t @ c) 15:48, 27 March 2017 (UTC)


 * Thanks for those comments. I will search for some cite to backup that last statement. The greater problem is there is no mention of the pulsar wind nebula anywhere in either the Crab nebula article nor the Crab pulsar article, even though they all shows image of the region. The problem also is to link this with the Pulsar wind nebula, which although I think I greatly improved still need much work - including some examples. (the same issue is with nova and nova remnant which I've recently updated. I'll need to sure the Crab Nebula's PWN is across all these pages. Needless to say, this would be an good improvement. My added text could then be arranged to suit from its present temporary location. Thanks.Arianewiki1 (talk) 11:17, 28 March 2017 (UTC)


 * , sounds good. You have the technical expertise, I'll handle grammar and style issues, how about it? — Huntster (t @ c) 16:26, 28 March 2017 (UTC)

I've been awaiting this arxiv article for a week or two, which was published today as "Pulsar Wind Nebula" by Patrick Slane. The location is here pdf is here  It clearly states: "First, while PWNe have, in the past, sometimes been referred to as SNRs (most often as a “center-filled” variety), they are, in fact, not SNRs." It states why in the text that folows. Hence, this should be removed in the Wpage. This shows the SAO is incorrect as well as the caption.

Notable is Figure 1a (pg.4), showing the size of the Crab SNR with the PWN inside. (A Crab Nebulae PWN article might be following in the next day or two.). Arianewiki1 (talk) 05:27, 29 March 2017 (UTC)


 * , nice article! I like how it describes the joint SNR/PWNs as a "composite SNR". Perhaps we can work that term into the article (and others) considering that the term "Crab Nebula", while specifically about the SNR, does act as a blanket, non-technical term for the whole assembly (I mean, they are intrinsically linked, both spatially and, I think, in any sort of public awareness). A section about the PWN and how it is a separate but related entity would round out the article nicely. Start there and then see if a full article is warranted? I'm just not sure that one is. — Huntster (t @ c) 18:36, 29 March 2017 (UTC)

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Observers used the Chandra X-ray Observatory to observe
184.17.203.207 (talk) 21:33, 23 July 2018 (UTC)


 * Changed to "Researchers". — Huntster (t @ c) 10:57, 24 July 2018 (UTC)

Lede

 * "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)