Talk:UY Scuti

Distance, luminosity and parallax

I've created this article. I am just a 13 year old boy, and I just get my information from SIMBAD. Please help me add some information about UY Scuti's distance, luminosity, and parallax, if you have any information about it. Thank you! Johndric Valdez (talk) 12:07, 11 September 2013 (UTC)

Error in size determination

I've just turned to the list of largest known stars, and found out that UY Scuti has errors in its size determination. I fear that maybe my information might had just don't make it contrary to current ideas. You can edit my article if new results were found to its size. Johndric Valdez (talk) 12:07, 11 September 2013 (UTC)

Largest known star?

At an astonishing size of 2.38 billion kilometres, or 1,708 solar radii, UY Scuti has now taken the place NML Cygni held for more than a year. Some websites are now reporting UY Sct as largest known star, and it was true at all, based on observations.

But according to a smart, good friend under the name Lithopsian, about a dozen stars were fighting for the throne. And it was true, candidates were VV Cep A, PZ Cas, RW Cep, KY Cyg, Wd 1-26 and WOH G64. And Lithopsian has provided a journal on the List of largest known stars that states UY Scuti has erroric scheme of estimate. Based on this data, if we relied on this, more candidates will follow. The reason that I've put only "one of the largest known stars" is because of what Lithopsian said that nothing has really changed, lots of stars are still competing for the throne. So don't start up shouting UY Sct as largest, there are erroric possibilities in size estimates, with uncertain predictions. If you don't understand then just ask Lithopsian, because he's the expert.

To Lithopsian, please add a reliable journal concerning this. I need your help. ==Johndric Valdez (talk) 06:14, 10 October 2013 (UTC)==

Mass correct?

The mass is given as 32 times solar mass. That seems impossibly low. — Preceding unsigned comment added by 94.226.172.196 (talk) 21:01, 15 December 2013 (UTC)

Why impossible? Red supergiants simply don't come much more massive than that. The mass is of course only an estimate based on stellar models that most closely reproduce the observed characteristics, but the models have been verified against other methods such as binaries and they won't be hugely wrong. Lithopsian (talk) 21:10, 15 December 2013 (UTC)

Supergiant or hypergiant?

UY Sct's spectral luminosity class and absolute magnitude fit it to become a hypergiant. Is this star a hypergiant or just a down-ranking supergiant? ==Johndric Valdez (talk) 12:06, 29 January 2014 (UTC)==

Hypergiant is not a term with a fixed definition. Specific to this case, red supergiants do not receive the O or Ia⁺ luminosity class because their spectra never show the relevant features, so hypergiant applied to an M star is simply a reflection of sufficiently high luminosity to place the star at the limits of stability, resulting in turbulence and high mass loss. The stability limit for all cool stars is placed at around M_V -9.5. Lithopsian (talk) 12:35, 29 January 2014 (UTC)

In the first paragraph in the article of VV Cephei, it states there that "Although VV Cephei is an extremely large star showing high mass loss and having some emission lines, the spectral luminosity class and absolute magnitude do not qualify it as a hypergiant." VV Cephei A has the spectral type M2Iab, which is not for a hypergiant. Some other stars, like VY CMa and NML Cyg all have spectral class Ia, and UY Scuti has too. Also, it is stated that VV Cephei A does not have enough luminosity, being 200,000 times that of the Sun. So far I haven't seen any hypergiant star below 250,000 times the Sun's luminosity (like VY CMa and NML Cyg both having 270,000). But UY Scuti hs 340,000, so it may fall into the class of hypergiants. ==Johndric Valdez (talk) 14:18, 30 January 2014 (UTC)==

I refer you to the definition section of the hypergiant article. It says all there is to say really and I can't add to it (especially since I wrote it!). Under that definition VV Cep fails completely to be a hypergiant. You can argue about whether any red supergiant should be called a hypergiant or not, but the term has been commonly used by astronomers, some of whom are as keen on populist hyperbole as anyone else, and by the press release folks who are paid precisely to attract the attention of the public with fancy words like hypergiant whether they're appropriate or not. On Wikipedia we should at least be internally consistent and any star classified here as a hypergiant should fit the definition given in that article. If you feel the definition is wrong then feel free to change it, supported by suitable references of course. Lithopsian (talk) 15:14, 30 January 2014 (UTC)

Kick Up A Fuss, Big Error Deals

I am going to bring back what I've said above. Lithopsian was right. Almost all pages concerning the largest stars in the Internet only base their claims on here in Wikipedia. One edit here and hundreds (thousands?) will claim it. Too bad they only claim what they see here (like the table in the list of largest known stars page) and do not study those refs.

In just a matter of few months, I was surprised how many reports in the Internet claim UY Scuti defeated NML Cygni in the first place when the fact is UY Scuti is the more likely to be defeated. Simply this claim arouses because people only look at star rankings, not the references. So now, I would like to request, what about changing UY Scuti's size from 1,708 ± 192 solar radii to 1,515-1,900 solar radii (like on AH Sco. Lithopsian changed it from 1,411 ± 124 solar radii to 1,287-1,535 solar radii) simply because people claim what is unlikely to be the largest known star.

Look, NML Cygni's estimate is very precise, 1,650 solar radii, no more nor less. We can't figure it out on UY Scuti; we are not sure about the size, yet the Internet claims because it was in the highest, not understanding the refs. If we did the 1,516-1,900 figure, we will push him to 4th place, below VX Sgr, and will rethrone NML Cygni. We must do that because I don't want people to claim the largest star as a star with errors, rather a star with a sureball estimate. Johndric Valdez (talk) 14:22, 18 February 2014 (UTC)

I'm not comfortable claiming either of these stars is "the largest". Certainly not based on a single paper (each) using different methodologies and where the likely errors are much larger than the differences between the two stars. But if someone wants to have a table of the largest stars then one star will have to be at the top and it will have to be the one with the largest reported radius, reported by us in as unbiased and consistent a way as possible, not using our own preferences to get one star or another to the top, however well intentioned that might be.

It isn't fair to say that NML Cygni has a radius of 1650, no more nor less. That is a number that doesn't even appear in the referenced paper. I know because I am the one who typed it in to Wikipedia and I was uncomfortable when NML Cygni ended up at the top of the list, even more uncomfortable when it got featured on the Wikipedia home page because of it. That number is merely implied by the temperature and luminosity given in the referenced paper, both of which have margins of error. I simply didn't feel it was appropriate to quote a margin of error on the radius, just quoting a calculated radius was as far as I was prepared to push "own research". Also, for UY Scuti it isn't fair to say that 1,708 ± 192 is the same as 1,515-1,900. The margin of error quoted in scientific papers has a very specific meaning, and it doesn't mean that the figure is definitely somewhere between two numbers. It could be larger or smaller, but with decreasing likelihood. I quote a range of values where different papers quote different values. I rarely include a margin of error simply because most people will misinterpret what it means. For these two stars specifically, one radius measurement is based on the assumption of a circular disk of a uniform effective temperature leading to a given luminosity, assumptions which certainly aren't true. While the other bases the radius on the observed sizes of the disk at certain wavelengths based on observations of water and carbon monoxide (combined with an assumed distance). The two papers just aren't measuring the same thing. The UY Scuti number is actually more rigorously derived, although still almost certainly too high. In a range of measurements of objects all approximately the same size (as extreme red supergiants almost certainly are) with random observational errors, the star found to be largest is simply the one with the largest error.

All of which makes a table, and especially a single largest star, even more meaningless. Is 1500 bigger or smaller than 1400-2400? Is 1500±500 bigger or smaller than 1400? Maybe we should put KY Cygni to the top (or W1-26) since it has the largest quoted radius at 2850, but that number is almost certainly wrong, even the authors of the paper say so. So I think we should only quote the numbers we get from the references, and then order the table in accordance. Lithopsian (talk) 14:58, 18 February 2014 (UTC)

Maybe we should take it to those "list of (superlative) stars" articles - problem is laypeople love those sort of facts so we can try and make them as buffed as possible. Cas Liber (talk · contribs) 20:34, 18 February 2014 (UTC)

What does UY mean?

What does UY mean? — Preceding unsigned comment added by 82.139.81.0 (talk) 20:36, 12 March 2014 (UTC)