Talk:WOH G64

Size[edit]

Does "size of WOH G64" mean diameter or radius of this star or something else? White rotten rabbit (talk) 09:50, 1 April 2009 (UTC)[reply]

I have clarified the dimensions based on the referenced paper.Lithopsian (talk) 22:26, 19 May 2012 (UTC)[reply]

It is Solar Radius. If you want to convert it to kilometers do the size in Solar Radius x 1,390,176.13. Cosmicwolfanimations (talk) 15:28, 10 February 2024 (UTC)[reply]

Actually don't do 1,390,176.13, it should be 1,391,400. Cosmicwolfanimations (talk) 21:37, 6 March 2024 (UTC)[reply]

WOH G64 was the largest in 2013?[edit]

I'll mention one (of many) very obvious problems with establishing a timeline. NML Cygni is listed as having a radius of 1,650 R_☉ and being the largest star from 2012-2013. The NML Cygni article currently cites a size of 1,050 R_☉ (or 1,183) from a 2010 paper. Clearly it wasn't the largest known star in 2012 or 2013. Possibly it was the largest star as reported in Wikipedia, but it hardly makes sense to be reporting that if we now know it was wrong. Lithopsian (talk) 19:50, 13 August 2016 (UTC)[reply]

It was WOH G64 the largest from 2012 ? — Preceding unsigned comment added by Red Planet X (Hercolubus) (talk • contribs) 20:38, 14 August 2016 (UTC)[reply]

Who knows? That's the whole point. It is almost impossible to know, almost pointless even asking, and certainly not sensible to put it in Wikipedia without a lot better supporting research. Lithopsian (talk) 20:43, 14 August 2016 (UTC)[reply]

Section probably should go. Largest star is wrong anyway. Better would be largest known, but as size may shrink as remeasured that sounds wrong too. Largest measured known stars... -Koppapa (talk) 11:42, 20 August 2016 (UTC)[reply]

It is the largest reliable, at 1,540 Solar Radius Cosmicwolfanimations (talk) 22:06, 10 February 2024 (UTC)[reply]

Turns out NML Cygni was never the largest star after all in 2012-2013, as I found the following information:

1,650 R☉ is NML Cyg's old size. The Zhang's reference says that size was 1,650 (-2,775) R☉ and the temperature (2,500–) 3,250 K and the De beck's reference says that the temperature is 3,834 K, If NML Cygni's temperature is 3,834 K, it means that NML Cygni's size is 1,183 R☉, If it is 2,500 K, its size would be 2,775 R☉ etc... because when the stars become warmer, they shrink, and cooler, they grow and the size of a giant, supergiant, hypergiant stars can change quickly. NML Cygni is listed as having a radius of 1,650 R☉ and being the largest star from 2012-2013. The NML Cygni article currently cites a size of 1,050 R☉ (it means that its temp is 4,074 K) from a 2010 paper. Clearly it wasn't the largest star in 2012 or 2013, It was WOH G64 (Not V838 Monocerotis because it was 380 – 1,570 R☉) with a size of 1,540-2,000 (jumk.de) R☉. And in general, when a range, use the small end of the range to sort, not the high end or some middle range and margin of error is not a range.

The 1,183 R☉ ref was made in 2010, so NML Cygni was only 1,183 R☉ all this time??????? I still use the old 1,650 R☉ for NML Cygni. So the 1,650, 2,208.5 and 2,775 for 2012 was never true. --Joey P. - THE OFFICIAL (talk) 05:19, 2 August 2017 (UTC)[reply]

We don't know the "true" size of any of these stars, and the margins of error in the values we do have are huge. Given that it is likely that the largest red supergiants are all a very similar size, the "largest known star" is likely to be the one which has the largest error in our current published values. For NML Cygni, two authors (de Beck and Zhang) have published slightly different data. Both are recent, but Zhang's is more recent and specifically about NML Cygni, with a new accurate distance. De Beck's paper is generic, calculating values for a wide selection of stars, and in other circumstances it would not be the preferred reference in the article. However, Zhang does not publish a actual radius so we would have to calculate it for ourselves which is less verifiable in Wikipedia terms. He doesn't even derive the temperature and luminosity, only adopted values from earlier (much older than de Beck) work, rescaled to the new distance. So we quote Zhang's distance and de Beck's physical properties. With a different approach we might just say that NML Cygni is somewhere between 1,183 R_☉ and 2,770 R_☉ (derived from 270,000 L_☉ and T_eff 2,500 K which even Zhang says is an unsatisfactory temperature) with similar very large ranges for other stars, which would be neither right nor wrong but very unclear. Which is why we don't have a timeline of which star was the biggest when. Remember, none of these stars changed size (that we know of), we just keep changing our guesses. Lithopsian (talk) 10:36, 2 August 2017 (UTC)[reply]

Also, I found these Portuguese videos that claim WOH G64 to be the largest star:

https://www.youtube.com/watch?v=aRf4JRyj2Ko https://www.youtube.com/watch?v=oOog-I9z0mQ — Preceding unsigned comment added by Joey P. - THE OFFICIAL (talk • contribs) 06:28, 8 September 2017 (UTC)[reply]

I could create a YouTube video and claim I was the largest star (might be fun to see how long before someone creates a Wikipedia article about me!), but it wouldn't be a very reliable source. The video creator might be a professional astronomer (or astronomical agency PR hack), but more likely it is some guy (or boy) in a basement who likes big stars and doesn't have a very robust approach to verifying the data. Or maybe just liked the name and went out searching for data to make it look like the largest star. Or it might even be a deliberate hoax - ever heard of fake news? Lithopsian (talk) 13:57, 8 September 2017 (UTC)[reply]

I have heard of fake news before, but what they didn't know is that they were right in real life... ----Joey P. - THE OFFICIAL 00:38, 14 September 2017 (UTC)[reply]

Good. I edited NML Cygni on the list of largest stars. — Preceding unsigned comment added by Joey P. - THE OFFICIAL (talk • contribs) 04:32, 3 August 2017 (UTC)[reply]

Also, Emily Levesque said that WOH G64 was the largest star. --Joey P. - THE OFFICIAL —Preceding undated comment added 04:22, 10 September 2017 (UTC)[reply]

Levesque et al specifically said that WOH G64 wasn't the largest star. Read the paper again. There is a question mark in the title, and even the abstract makes it clear that previous authors had derived properties which could indicate it was the largest star, but the new paper said it was just comparable to the other largest red supergiants (1,540 R_☉, still in the article). A key previous paper being referred to was van Loon (2005), study of multiple AGB and red supergiant stars, which didn't state a radius but did derive luminosity and temperature that would indicate a radius around 2,500 R_☉. So WOH G64 is one of the largest known stars and likely the largest in the LMC. Lithopsian (talk) 11:14, 10 September 2017 (UTC)[reply]

I have seen that the largest star in Levesque et al's documents is VY Canis Majoris, with a claimed radius of 3,020 R_☉. ----Joey P. - THE OFFICIAL 00:38, 14 September 2017 (UTC)[reply]

Levesque et al (2005) didn't refered VY CMa as the largest star but stated that the estimated radius of 3,020 R_☉ (which came from Monnier et al. 2004) for VY CMa is too large and may also violate the stellar evolutionary theory. Read the paper again. ZaperaWiki44 (talk) 07:12, 14 September 2017 (UTC)[reply]

Preferred sources[edit]

WOH G64 is now listed in a number of large databases of red supergiants, all produced within the last two or three years. These produce some wildly-different estimates of the luminosity of this strange object. Davis & Beasor (2020) explains why most of these, and their own 2018 paper, produce the wrong luminosity. Put simply, WOH G64 does not emit the same amount of energy in all directions so you can't just add up what we see and multiply it over a sphere. Ohnaka et al (2008) shows the WOH G64 is surrounded by a dusty torus which absorbs much of the visible radiation and emits it as infrared. Levesque et al (2009) re-calculated and got similar results. Any bulk calculations of properties for thousands of stars that don't take this into account should not be relied on. Now, which sources are we going to use? Lithopsian (talk) 20:42, 16 June 2020 (UTC)[reply]

The 1,540 to 1,730 solar radii estimates are probably the best to use. Nussun05 (talk) 14:25, 7 August 2020 (UTC)[reply]