Talk:Mu Cephei

Distance

There is a contradiction in the article. The text reads a distance from the sun of 3000 ly, the infobox reads 5000. Arasaka 18:32, 27 December 2006 (UTC)

More contradiction

From the infobox: Distance approx. 5000 ly (approx. 2000 pc)

The page on parsecs says a parsec = 3.26 ly. If that's the case, 5000 ly could not equal 2000 pc. If the 2000 figure is correct, then the star would be about 7000 ly away. 4.243.146.153 18:12, 6 January 2007 (UTC)

The 5000 ly value apparently comes from the Hipparcos parallax (0.62 ± 0.52 mas). If it is a member of the Cepheus OB2 association, the distance is 2400 ly (see Jim Kaler's Stars). Measured angular diameter suggest that the star is more farther, at 2800 ly. It is obvious that 5000 ly is too much.--JyriL ^talk 18:44, 6 January 2007 (UTC)

CalRis (talk): I removed the parallax/distance info from data box. Reason: the values given are totally unreliable. These values given for parallax (taken from the Hipparcos catalogue) are (in this case) useless due to large error margin. No surprise there, however, as it is a trigonometric parallex, and at these distances... For more information see the reference I added to the article. Bye. —Preceding comment was added at 11:21, 18 March 2008 (UTC)

There is also a discrepancy/contradiction between the radius of the star as stated in the info box and the first sentence of the 2nd paragraph in the Properties section (1,650 solar radii) and the last paragraph relating to the ring of material around the star. If the star's radius would extend to between Jupiter's and Saturn's orbits (as stated in the second paragraph), how can the ring which starts at 2 times the star's radius start around Jupiter's orbit (1,300 solar radii)? These two values are incompatible - the ring starts within the body of the star???

NB: 1,300 is twice 650. Could the 1,650 solar radii value be a typographic error with an extra 1 added? That would reconcile the difference between the values. However, I have found a reference (http://stars.astro.illinois.edu/sow/garnet.html) that states the radius of mu Cephei to be 1,650 solar radii as determined by its angular diameter.

I have since reviewed the reference used for mu Cephei's radius in the info box. Nowhere does it state that the radius is 1,650 times solar, rather the paper, which is also the source of the data regarding the ring of material around mu Cephei, uses a value of 650 solar radii. Again this is incompatible with the value obtained by measurement of angular diameter.

—Preceding unsigned comment added by 65.39.8.74 (talk) 17:13, 14 April 2010 (UTC)

Agreed. I came to this talk because the 1650 appeared to be a typo of the 650 actually given in the reference, albeit that was a figure accepted from a different paper and not found by the referenced paper. A quick calculation from the other physical parameters of luminosity and temperature shows that 1650 is simply wrong. I will correct this here and on the largest stars page, with reference to at least two papers. Much of this article is hyperbolae about how big the star is, but for now I will leave that text and just add a footnote. — Preceding unsigned comment added by Lithopsian (talk • contribs) 12:19, 20 May 2012 (UTC)

Reddest of all stars

Some author Ahad (astronomer) (UK, Bangladesh 1968-) rated it as _the_ redest based on (B-V)

File:Ahad redstars chart.jpg

I wonder how much of this reddening is down to interstellar ex~tinction? —Preceding unsigned comment added by 80.176.196.73 (talk) 12:17, 16 July 2008 (UTC)

I think it is not by far the reddest. F.ex. searching the Hipparcos catalogue, I found HIP 344 being of B-V 3.91. Possibly it's one of the redder naked eye stars. Interstellar "reddening" is mainly a cutoff at the blue end, so that the probably blue Deneb appears as white for us. ... said: Rursus (bork²) 21:31, 25 January 2009 (UTC)

"Garnet" Sidus?

What kind of Macaronian is that? Garnet is English for a red stone whose name is Carbunculum in Latin. Sidus is Latin. I've never ever heard the weird combination "Garnet" Sidus and it doesn't sound well in my ears. I've heard "Granatis", but never "Carbunculum". I think Herschel's real name is "Garnet Star", not anything else. Said: Rursus (☻) 22:46, 17 October 2008 (UTC)

The text is so formulated that it is easy to get the impression that Piazzi named it. I believe William Herschel did, not Piazzi. Piazzi was the first to catalogue it, possibly there naming it "Garnet Sidus" (see Richard Hinckley Allen), explaining the very weird (and in my non-English ears: very ugly) mix of languages. Said: Rursus (☻) 22:57, 17 October 2008 (UTC)

It.wikipedia says "Granatus Sidus", which might be the cause of this bastard "Garnet Sidus", "Granatus" is an error (like the "Carbunculum" I did above), "Granatum" is pomegranate/Punica granatum ("Carbunculus" is garnet/Garnet of the pyrope kind/Mg₃Al₂(SiO₄)₃). I wonder which... Said: Rursus (☻) 08:24, 18 October 2008 (UTC)

Error again: "Carbunculus" is Almandine garnet. Said: Rursus (☻) 11:03, 18 October 2008 (UTC)

Or, why not hand grenade? Said: Rursus (☻) 08:26, 18 October 2008 (UTC)

Surveying by simply googling: the following combinations are nonexistent on the net:

1. Granatum/Granatis + "Mu Cephei"
2. Carbunculus/Carbunculum + "Mu Cephei"

the following is very very rare:

1. Granatus + "Mu Cephei" (circa 7 hits)

Forget about Granatum and Carbuncle-whatever! (We may also safely dismiss hand grenades, I think). I believe μ Cep was called like a stone and in the English language, while some bad translations might have occurred somewhen in the early 1800ths. Said: Rursus (☻) 11:26, 18 October 2008 (UTC)

I fixed it.Masursky (talk) 01:08, 25 November 2008 (UTC)

Luminosity vs. distance uncertainty

Hello,

I am not a wikipedia editor, but I have some background in astronomy and thus I have a point for the considerations of whomever is willing to work on the article:

If we are unsure in the distance by a factor 4, as it is implied by the article, we are unsure about the absolute lluminosity by a factor of 16, because the apparent brightness (which is known) varies as the square of the distance. Then the figure of "350 000 solar luminositites" has no meaning (why to even give two significant figures if we may be out by more than an order?). Moreover, the large uncertainty in distance and thus absolute luminosity may significantly affect the estimates of size etc. which are given in the article as quite sure fact.

Suggestion: either provide a more precise value of the distance or soften the statements about the other parameters of the stars. In the way in which the article is written, it is contradictory.

Greetings, Jan Ebr

78.128.164.122 (talk) 16:50, 8 April 2009 (UTC)

Edits done by 67.110.176.68

Since this IP address has an extensive history of vandalism I will revert any edits done by this IP. If anyone from this IP wants to edit this article you will need to provide references to back up your edits before I will allow the edits to remain. Dr. Morbius (talk) 20:40, 17 December 2009 (UTC)

Size

Isn't the line about this being the largest star in the galaxy a bit over the top? - given that there are dozens of stars that are larger: http://en.wikipedia.org/wiki/List_of_largest_known_stars 65.215.33.194 (talk)KC — Preceding undated comment added 16:45, 29 August 2014 (UTC)

Removed the chunk under the "properties" section, where it jarred. That it is one of the largest stars in our galaxy is correct, and remains in the lede. Tarl.Neustaedter (talk) 20:34, 29 August 2014 (UTC)

VV Cephei is a naked eye star. Lithopsian (talk) 22:32, 30 August 2014 (UTC)

There was a typo in one of the refs, where it said 650 R_☉ it said 1,650 R_☉ and that value left a heavy footprint on the internet. Mu Cephei is now between 1,260 R_☉ to an upper limit of 1,420 R_☉. --Joey P. - THE OFFICIAL ^{(Visit/Talk/Contribs)} 17:41, 25 October 2017 (UTC)

I don't think 1,650 R_☉ is a typo. It appears on Kaler's page, with just enough information to work out where it came from. He reports a distance of 2,400 light years, which is 736 parsecs, and describes the angular diameter being measured at 0.021". I looked up the actual angular diameter of 20.584±0.480 mas (limb-darkened, actual measured value is smaller), which calculates out to almost exactly 1,650. Note that his book contains a different value, apparently based on the uniform disk angular diameter of 18.672±0.435 mas or perhaps on an older measurement. I will add this to the article since there doesn't seem to be any mention of a measured angular diameter in there. Lithopsian (talk) 14:42, 20 September 2018 (UTC)

The value 650 R_☉ is also not very meaningful. Apart from being old (2000, like ancient history man!) it is simply an assumption that μ Cep was more or less like Betelgeuse. More recent observations suggest it is much larger and more luminous, so the adopted model from this paper probably shouldn't be used, except perhaps in discussions with the body of the article. Lithopsian (talk) 15:23, 20 September 2018 (UTC)

Since UY Scuti is the only star known that's accurately estimated over 1,650 solar radii (excluding Mu Cephei of course) and I'm pretty sure UY Scuti isn't even in the milky way galaxy. VY Canis Majoris is now considered 861-1,420 solar radii and VV Cephei is now considered 1,050-1,400 solar radii. JayKayXD (talk) 02:10, 12 October 2018 (UTC)

First, the 1,708 R_☉ for UY Scuti is considered dubious since it was based on a highly old distance (in 1970, which makes it pretty obsolete like what is also mentioned in the text and see talk) and should not be certainly considered the largest known star. Second, who the heck told you that VY CMa is only 722-861 R_☉??? Most sources (excluding Massey et al. 2006) say that it is over 1,200 R_☉. And also these values are certainly too low for a red hypergiant with a such huge mass loss as the mass loss is due to its high brightness. ZaperaWiki44^{(✉/Contribs)} 11:03, 12 October 2018 (UTC)

https://starchild.gsfc.nasa.gov/docs/StarChild/questions/question21.html. This website says 600-2,100 R_☉. It's probably useless for Wikipedia anyways since 722-861 R_☉ seems too small for stars like VY Canis Maoris. Also, someone on the list of lagest known stars said that UY Scuti 916 R_☉ but didn't have a source saying so. If we did manage to find a source with more recent calculations for UY Scuti's radius and says t's much smaller than 1708 R_☉, either Mu Cephei or Woh G64 would be the largest known star.JayKayXD (talk) 13:16, 6 November 2018 (UTC)

Properties

In the last paragraph in the section Mu Cephei#Properties is found the following: 6″. In Edit Mode one sees that this means "6 Prime", but for the non-expert, this 6" is mystifying. Is there any chance someone could clarify this in some way and/or link to an article that would explain it further? CorinneSD (talk) 16:22, 30 August 2014 (UTC)

That symbol means arc-seconds (or some other sort of seconds, but arc-seconds in this context). I don't know if it is policy to spell it out or not, but it could certainly get wikilinked. Lithopsian (talk) 22:34, 30 August 2014 (UTC)

Unclear nature of components

Are the components listed physically associated, or just optical? This information needs to be in the article. AnyOldBiscuit (talk) 07:55, 19 September 2018 (UTC)

Who knows? Find a reference and add it. Lithopsian (talk) 13:26, 19 September 2018 (UTC)

A Commons file used on this page has been nominated for deletion

The following Wikimedia Commons file used on this page has been nominated for deletion:

• Mu cephei size.png

Participate in the deletion discussion at the nomination page. —Community Tech bot (talk) 21:21, 13 February 2019 (UTC)

Radius

Should we put the 650 R_☉ estimate back in the article? Not in the star box obviously but in the size section? If we do though, we should mention why the 650 estimate likely isn't accurate and isn't usually accepted these days and why 1,260, 1,420 and 1,650 are better estimates.

Its obsolete and unreliable. Look where it came from, it is little better than a guess. I see no reason to put low-grade information in, except possibly as part of a history section, as in we used to think μ Cep was like Betelgeuse and now we don't. Lithopsian (talk) 09:26, 15 August 2019 (UTC)

That was just one paper. It was always usually estimated to be larger and much more luminous than Betelgeuse. Most recent papers also put it at slightly hotter than Betelgeuse. Belelgeuse is likely barely 100,000 L_☉ if even 100,000 at all. Mu Cephei is usually estimated to be at least 250,000. Also, multiple papers suggest that Betelgeuse is under 1,000 R_☉. The lowest reliable estimate for Mu Cephei that I could find is 1260. I've seen as large as 1650 in Kaler's page. It may even be larger than 1650 since Kaler put it at 2400 light years away when 2840 is the most accepted value these days. There's a good chance that Mu Cephei is the largest naked eye star (debatable with VV Cephei) and possibly even the largest known and Betelgeuse just seems like a normal red supergiant that's about to go supernova. However, the 650 R_☉ estimate is mentioned in the notes for Mu Cephei in the list of largest known stars so why isn't it mentioned here?JayKayXD (talk) 20:36, 15 August 2019 (UTC)

See WP:OTHER, in other words just because there is crap in other articles (and list of largest known stars is certainly an article with a more than average amount of crap) doesn't mean it should be here. You've just explained that a completely obsolete, and apparently incorrect, value for the radius was derived by a single paper. Nobody today thinks it is even close to being the likely radius. Why would you want it in the article? Time to move on. Lithopsian (talk) 20:51, 15 August 2019 (UTC)

If there's so much crap in the list of largest known stars article then just remove it.JayKayXD (talk) 03:29, 16 August 2019 (UTC)

I do, regularly. It comes back. Check the history, its quite something! Lithopsian (talk) 11:35, 16 August 2019 (UTC)