Talk:VY Canis Majoris/Archive 1

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Archive 1

Hypernova 3200

Why do scientists think it will hypernova in only 1200 years. Even though this star is in the terminal phase of its existence, it may not hypernova for 100,000 years. Why do they have a date. How can they know this --142.176.13.19 22:27, 9 August 2007 (UTC)

It's an un-referenced addition by an IP editor. I'm removing it. Hatch68 16:45, 9 October 2007 (UTC)

162000 yr calc seems off

That 162,000 yrs calculation is way off. If VY is 2100x the radius of the Sun, which itself is 109x the radius of earth, then the circumference of VY is 2100*109 times the circumference of the Earth. Since 109*2100 is about 229,000, then if it took someone 2.9 years to walk Earth's circumference doing about 24 miles a day, then 2.9 years * 229,000 is about 664,000 years to walk the circumference of VY Canis Majoris. Mark --70.108.162.180 02:25, 17 June 2007 (UTC)

Others authors (Monnier 2004; see page #16 of [[1]] give an even larguer size for that star; the radius of 14 AU given there correspond to a real radius of 3000 times the one of our sun. However, it assumes a low temperature for the star.

I did find the numbers for this star. Please keep them in reference while you edit the page. I just might go ahead and add them if I can.

HIP 35793 HD 58061 SAO 173591

Reference is SIMBAD Thanks so much.. —Preceding unsigned comment added by 71.209.88.139 (talk) 02:28, 4 July 2008 (UTC)

Maximum star size

Does anyone know why "the largest possible star is approximately 2,600 times the radius of the Sun"? Louis Waweru Talk 22:45, 4 July 2008 (UTC)

Eddington luminosity.Geni 10:08, 1 September 2008 (UTC)

Original research for walking time?

Uh, is that walking time estimate listed anywhere? Also, is it even necessary to have a walking time estimate given that nobody will ever walk around that star? There are better ways to give a size comparison than a walking time estimate. —Preceding unsigned comment added by 75.43.36.45 (talk) 00:45, 30 September 2008 (UTC)

I had tagged it as WP:SYN but that was removed. If anything it's just a useless comparison that probably should be removed. --George100 (talk) 00:57, 30 September 2008 (UTC)

Some people have trouble with really big numbers. But somehow, if you compare those numbers to money, then they can make a relationship. Like saying if the Earth was $1, then .... they get it. Try it with someone and you'll see.Nelfer (talk) 15:03, 3 October 2008 (UTC)

I assume , and we all know what happens when you assume something.

Since all things rotate around a something, The Earth rotates around the Sun, the Moon around Earth, what does this giant rotate around. This is scary. — Preceding unsigned comment added by 65.89.12.2 (talk) 11:31, July 2, 2007

Around the center of the galaxy. --142.176.13.19 22:27, 9 August 2007 (UTC)

Yeah, around a cluster of stuff. 64.231.84.236 (talk) 03:49, 11 January 2009 (UTC)

It either rotates around an object with an even stronger gravity field, or not at all (stellae fixae) - 145.103.105.1 (talk) 13:10, 2 February 2009 (UTC)

The term is "revolve," not "rotate." Rotation is the movement of a body on its axis, while revolution is the movement of a body around another body. Anyway, back to the subject... in the case of the Moon revolving around the Earth, for example, it is not only the Moon revolving around the Earth. The Earth is also revolving around the Moon. However, since the Earth is much heavier than the Moon, the center of gravity lies so close to the Earth (imagine trying to balance a huge boy and a little boy on a seesaw; you'll have to place the huge boy nearer the fulcrum of the seesaw), that its revolution around the Moon becomes imperceptible. So what does VY Canis Majoris revolve around? Probably another star that is so small and so dim it is lost in the light of huge VY Canis Majoris, that bully. Or, it could be a lone star, just like our Sun, and peacefully revolves around the center of the Galaxy. Micasta (talk) 10:20, 27 February 2009 (UTC)

Photo of VY Canis Majoris

I embedded a photo of VY Canis Majoris taken from HubbleSite. Micasta (talk) 04:25, 3 March 2009 (UTC)

RED

Firestorm's change constitutes vandalism. VY Canis Majoris is red, not yellow. Firestorm is not the first to vandalizate this page. the word red has been changed to yellow before, and the change was reverted be me, but the page was re-vandalised by Firestorm. I've reverted his change. —Preceding unsigned comment added by 87.68.100.128 (talk) 18:27, 19 March 2009 (UTC)

Saturn in the bath

Article says:

If a human could walk on the surface of Canis Majoris...

Yeah, if the Moon would be a green cheese! Or, if Saturn was put in a huge ocean. Said: Rursus (☻) 21:16, 16 September 2008 (UTC)

I suppose the name Jon Osterman means nothing to you?

-G —Preceding unsigned comment added by 173.32.141.8 (talk) 17:24, 24 March 2009 (UTC)

size/luminosity controversy

Should the "controversy" about this star's size not be introduced in the lede? The way this article reads at the moment is almost like the second study which claims VY CMa is just a normal red supergiant is seen as a fringe idea or otherwise not generally accepted - for all I know, this may be the case, but it's not clear. The prominence of that contradicting paper should be explained in greater detail, whatever the case. - filelake shoe 14:07, 31 March 2009 (UTC)

You're right about that. I'm planning to add more regarding Massey's study when I get the time to do so. Micasta (talk) 14:11, 31 March 2009 (UTC)

I just finished reading Massey's paper and it's too technical for my understanding *groans*. An expert on the subject should probably be the one to write on this matter. ^^Micasta (talk) 01:13, 5 April 2009 (UTC)

Yep... I had the same problem, that it was too short and didn't explain the technicalities mentioned, which as an amateur astronomer I hadn't a hope with. Best guess I can make is that it's suggesting that with such a high mass and luminosity, it wouldn't be able to keep itself together at such a low temperature.

There's a bit of an inconsistency in it though, that it states the previously proposed size of VY CMa at 2800 solar radii, and I can't find any report that suggests it's that big. Perhaps if they did their calculations based on that figure then the study will have some flaws. - filelake shoe 17:46, 14 April 2009 (UTC)

Here's [2] an interesting article from the Sloan Digital Sky Survey that teaches how to calculate the radius of a star. I haven't gotten around to reading it yet (too busy...) but I think it makes use of Stefan-Boltzmann relations. I think this will help us understand what Humphreys and Massey are talking about. I've also found some recent articles (dating 2009) that contest that VY Canis Majoris is not as big as is popularly claimed. Micasta (talk) 04:49, 15 May 2009 (UTC)

oh oh

I just got to think of a thing, if the star Eta Carinae is 7.500 light years away from earth and when it becomes a supernova it might effect earth(i know its not a lethal effect but still ) and if VY Canis Majoris is 5000 light years away then what the hell happens when it goes supernova!? (if it does) :S Kitten!meow 19:11, 31 May 2007 (UTC) Kitten!Meow

Isn't mass the important factor when it comes to supernova effectivity? Well, I'm not a scientist so I wouldn't be sure. 124.106.234.29 (talk) 22:29, 21 March 2008 (UTC)

7,500 light years is a safe distance. A dangerous distance for a supernova would be about a couple hundred light years. Just read that off "Voyages through the Universe" by Fraknoi, et al. Micasta (talk) 10:11, 27 February 2009 (UTC)

Why isn't their a Hipparcos number, or an HD number?? I want to research this star farther on a universe simulation application that I have at home. Can someone put that number on the actual article?? Thanks..65.117.69.179 (talk) 17:47, 3 July 2008 (UTC)

Would it be possible for an event from Canis Majoris, be it supernova, hypernova, steller flare or any other outburst of radiation or energy to cause a chain reaction that would diretly effect smaller stars and therefore their orbiting planets? —Preceding unsigned comment added by ChrisRichards0672 (talk • contribs) 09:50, 22 May 2009 (UTC)

Date of Discovery

This article lacks the basic information of its discovery. —Preceding unsigned comment added by 81.106.37.137 (talk) 22:45, 5 July 2009 (UTC)

Size of VY Canis Majoris in the planetary comparison photo

Should it not be noted possibly in the corresponding caption that the size of VY Canis Majoris in the photo with the many other planetary or solar bodies is based on the lower estimate of 600 solar radii rather than 1800-2100? Although I am not the one to design the photo, it is rather obvious that this is the case. And, to the author of said photo, would it not be more impressive to have VY Canis Majoris increased to its upper size estimation? That is outside my control though, but I still think a clause should be added to the caption of the picture --Suic (talk) 23:14, 14 January 2010 (UTC)

Calculating the absolute magnitude

I used the following formula (see Absolute magnitude) to calculate the absolute magnitude of VY Canis Majoris: $M=m-5((\log _{10}{D_{L}})-1)\!\,$ wherein D_L is in parsecs. Using a distance of 1500 parsecs (which is uncertain, since stellar distances are accurate only up to about 100 light years[3]), and a visual magnitude of 10.19, I calculated an absolute magnitude of -0.69. This value is inconsistent with a luminosity of 2×10⁵ (which is also under dispute... I may contribute more on this in the future). I then used another formula (from Luminosity): $M_{1}-M_{2}=-2.5\log _{10}{\frac {L_{1}}{L_{2}}}$ I used the absolute magnitude of the Sun as benchmark. Let M₂ = 4.83. I calculate an absolute magnitude of -8.4. Which means at least one of the experimental values is inaccurate. Any thoughts on this? Micasta (talk) 01:57, 8 March 2009 (UTC)

SIMBAD says that the parallax of this star is 1.78 ± 3.54 milliarcseconds. Note the relatively large error. Hipparcos has measured the parallaxes of stars only up to 1,600 light years away (see article on Parallax), which is far smaller than the supposed distance of 4,900 light years for VY Canis Majoris. Using the formula:

\sin p={\frac {1AU}{d}}

(also from Parallax article), and a value of 1.78 mas for the parallax, I calculated a distance of 1830 light years. If I assume a parallax of 1.78 + 3.54 mas, I obtain a distance of 613 light years. For a distance of 4,900 light years, the parallax must be 0.67 mas -- well within the parallax recorded in SIMBAD, but still too inaccurate. Any thought on this? Micasta (talk) 10:15, 8 March 2009 (UTC)

It's little use using the parallax values you cite Micasta since the enormous error makes it invalid. Also your calculations are in error and you forget about correcting for "reddening" i,e, interstellar extinction. A useful recent article on the distance of VY CMa is Reid et al. (2009). Reid, M. J.; et al. (2009). "Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions". The Astrophysical Journal, in press 700: 137. doi:10.1088/0004-637X/700/1/137. http://arxiv.org/abs/0902.3913.

VY CMa being a maser imbedded in a nebula allowed for much more accurate trignometric parallax determinations using radio astronomical techniques. based on the Reid et al. data distance to VY CMA and the associated nebulosity is 1140 +/- 90 parsecs (3720 +/- 290 light years) equal to a parallax of 0.876 +/- 0.076 mas. Distance modulus is thus 10.28: (log10(1140)*5)-5 = 10.28. Its B-V (colour) is 2.24 which means roughly interstellar extinction (R) of its light is 1.6 magnitudes. This assumes M5-type stars have standard B-V of about ~1.7 (see Wikipedia article on interstellar extinction of light). Assuming maxima apparent magnitude (Av) for VY CMA is 6.6 and mean Av is 8.0 (minimum is 9.6) the estimated absolute magnitude would then be -5.3 and -3.9 (minimum is about -2.3), respectively. The -3.9 value is consistent with the AAVSO spectral type M5Ibpe(C6,3) (see http://www.aavso.org/vsx/), which is based on mean luminosity readings, presumably. Thus at maximum VY CMa is slightly less as luminous as Betelgeuse (Alpha Ori) or Antares (Alpha Sco) but is larger due to being cooler.

--Jb291266 (talk) 04:32, 22 February 2010 (UTC)

Question

is VY Canis Majoris located in the Milky Way ? Yes or No ? thank you Einkleinestier (talk) 15:18, 10 March 2010 (UTC)

Yes. Grayjack (talk) 20:58, 16 March 2010 (UTC)Grayjack

Wow

That size comparison w/the sun is absolutely mind-boggling. I have a hard time believing that a star could be that large.C1k3 07:46, 9 February 2007 (UTC)

Agreed- the sheer scale of the Universe and the things in it takes my breath away at times. --Ifitmovesnukeit 19:44, 2 May 2007 (UTC)

And to think this is only the biggest star that WE know of. Holy cow, the biggest one must be HUUUUGE. 66.61.37.37 (talk) 21:50, 5 March 2009 (UTC)

Yo momma so fat, she's bigger than a ja jestem cwelemVY Canis Majoris! -- Zondor 20:49, 9 May 2007 (UTC)

The term "giant monster giga star" can't even begin to describe this. 206.107.103.85 (talk) 21:37, 23 March 2010 (UTC)

This star is pure terror...but what is "his" life span? I thought the bigger they are, the sooner they transform all their hydrogene and die. —Preceding unsigned comment added by 87.182.125.83 (talk) 02:32, 25 July 2010 (UTC)

VY Cma is not an exceptionally short-lived or massive star. The most massive stars, more than about 40 times the mass of the sun) don't ever become red supergiants but explode as supernovae within about 5 million years. Lifetime decreases dramatically at higher initial mass, and the most massive stars known probably don't live more than about a million years. At around 25 solar masses (a likely initial mass for VY CMa), stars start evolving towards red supergiants at about 7 million years, then gradually expand and become more luminous over another million years or so until they explode as supernovae. By that time they have lost around half their initial mass. VY Cma is seen in that tiny window of a few thousand years as it nears the largest size possible for a star. Lithopsian (talk)

Apparent magnitude=

The apparent magnitude is specified as 7.9607. Is four digits after the decimal point not completely obsolete ? Stellar magnitudes expressed even with two decimals results in an error of 2.512^0.01 = 1.0092 which is less than 1 percent and brightness determination can be achieved at an error of at most 1%, so in this case, 7.96 is sufficient. S k a t e b i k e r (talk) 10:46, 26 July 2010 (UTC)

Mass

There are two different theories of upper mass limit of red supergiants.

One theory says the mass limit is about 40 times solar masses. The other theory says the mass limit is about 25 times solar masses.

If the characteristics in wikipedia pages of the two red supergiants "VY CMa" and "VV Cep" are accurate , the former mass limit is correct. But the simulation tracks of steller evolutions by the current theory accord with the latter mass limit.

I hope the former mass limit(40 times solar massses) is correct.

Kometsuga 16:07, 24 November 2006 (UTC)

Changed size description from hypergiant to a super giant star, despite its size, YV CM is not a hyper giant, it lacks mass of hyper giant star, to qualify for title of hyper giant star must exceed 90 mases of sun, VY CM is less than 40. —Preceding unsigned comment added by 188.220.53.72 (talk) 13:38, 4 August 2009 (UTC)

If this star really is only 25 Solar masses, then it's density (might be wrong, I calculated it myself) would be much less than hydrogen's density. Can't understand how that could be possible, but I guess it must be. I'd like to see it counted on the article, maybe in the infobox.85.217.39.41 (talk) 19:32, 25 March 2010 (UTC)

I'm asking again. I calculated with 600 times the size of the sun and with the density of HYDROGEN, and got 13,788 (13 thousand) solar masses. Not very dense, eh? I also calculated with the 1800 currently on article and got 372,287 (327 thousand) solar masses, also with the same density (hydrogen).

With current minimum size in the article (600) and maximum mass (40) I get a density of 0.00000026×water or 0.003×hydrogen. These can't possibly be right, can they? It can't be a star with a density of 3/1000 of hydrogen. 82.141.117.133 (talk) 04:03, 26 November 2010 (UTC)

Yes the star would be very tenous. Hydrogen (or anything else) does not have a single density. You are comparing a gas at room temperature and atmospheric pressure with gas/plasma at thousands of degrees and very low pressure. The hotter the gas and plasma get and the less pressure they are under the further the atoms will be apart on average, thus massively lowering the measured density. Just like the upper atmosphere of the earth it wold be very hard to tell where the star ends and space begins. LiamE (talk) 18:58, 19 January 2011 (UTC)

Parent Galaxy

This thing is in our galaxy, right? If so, I suggest adding that fact. Or is it just understood that stars with Wikipedia pages are in the Milky Way unless otherwise noted? Jyoshimi (talk) 22:14, 30 May 2008 (UTC)

Yeah... I don't think we can even observe stars in other galaxies. We can barely see the entire (other) galaxies, let alone the individual stars within them. Yes, this is all in our Milky Way.Nelfer (talk) 14:55, 3 October 2008 (UTC)

You're wrong, Nelfer. Read on the observable universe and galaxy articles. We can observe other galaxies. 64.251.85.182 (talk) 20:09, 14 November 2008 (UTC)

I know we can see other galaxies. I was refering to the fact that we don't have the power to see individual stars and examine them in other galaxies, only within our milky way. If this has changed, then when talking about a star, we should specify in which galaxy is found.Nelfer (talk) 16:36, 29 June 2009 (UTC)

We can see such stars, read WOH G64 for instance, which is the second largest known star currently, but isn't in our Galaxy. However I feel it probably isn't necessary to specify that a star is in the Milky Way, as most known stars are. Certain facts in the article do make it pretty obvious, e.g. the fact that it's only 1.5 kiloparsec away. - filelake shoe 20:45, 29 June 2009 (UTC)

Much of the strong evidence of the distance of galaxies is down to observing individual cepheid variables within them. LiamE (talk) 19:06, 19 January 2011 (UTC)

The Number of significant figures for its size.

The Number of significant figures for its size, 3.063 billion km, is way over the top. Dave3457 (talk) 22:46, 15 June 2011 (UTC)

New size comparison image

I made a new size comparison image. I feel that it is a bit cleaner than the main image for the article. I also think that it gives a better feel for the relative size of the star. I would like to change the main image to my one, thoughts?

Stephen.G.McAteer (talk) 23:40, 29 September 2011 (UTC)

Sorry, the work is appreciated, but I find it confusing. What is the significance of the two "44"s? Also the current starbox image is quite good I think. Bhny (talk) 00:16, 30 September 2011 (UTC)

Fair enough. The x44, x109 is the magnification factor at each of those steps. I agree that the current image is quite nice. Stephen.G.McAteer (talk) 22:23, 2 October 2011 (UTC)

Contradiction

The page stated in the introduction that this was the second largest known star, and later in the page that it was THE largest. The addition of "Second" was a recent edit, and in contradiction with the article linked to by the same phrase, so I went ahead and fixed this, 86.28.149.134 (talk) 19:18, 22 July 2010 (UTC)

That edit was in error due to confusion arising from the discovery of R136a1, which has been fallaciously reported as "the largest" star by newspapers which mean to call it "the most massive". The two are different measurements - the latter is measured in solar masses, of which R136a1 has more, while the former is measured in solar radii, a measurement I can't find in any of the sources for the new discovery. - filelake shoe 06:53, 23 July 2010 (UTC)

I would like to point out that the Eta Carinae article mentions the possibility that if it went hypernova at 7,500-8,000 ly away, and the poles were angled at us that it could have a 1KT TNT/sqkm effect on the hemisphere facing the GRB + lethal does of radiation, but since it isn't the effects of the hypernova would likely be reserved to upper atmosphere, satellite and any Astronauts in orbit, yet Canis Majoris at 4,500 ly away would cause no risk for us at all if it went hypernova?? That would seem to be a problem, especially how much more mass Canis has to eject. IT would seem we would have to have at least some risk of damage from a more massive star undergoing the same cataclismic event at nearly half the distance. I'm not scientist but as an interested layperson, that makes no sense to me.

Eta Carinae has about 100-150 solar masses to eject, VY Canis Majoris has about 40 solar masses to eject. Though the radiation from a possible GRB woulld effect us much more than Carinae's, so you at least have a point. 72.28.15.25 (talk) 21:05, 15 February 2012 (UTC)

Beyond the orbit of Uranus?

First comparison of the star's radius made in regard to a planet's orbit refers to Uranus which is obviously wrong since the correct comparison is made regarding Saturn in the "Size" section. Unless of course, "[it's] surface would extend beyond the orbit of Uranus..." means something else other then radius comparison. — Preceding unsigned comment added by 92.250.30.93 (talk) 02:14, 6 March 2012 (UTC)

Absolute Magnitude

-2.919756295 Can someone add this? --108.225.229.48 (talk) 04:00, 22 March 2012 (UTC)

New paper, March 23 2012

If I find a moment in the future I'll make some edits myself but it's probably worth noting that this new paper on the object appeared on the arXiv a few days ago: Fundamental properties and atmospheric structure of the red supergiant VY CMa based on VLTI/AMBER spectro-interferometry Warrickball (talk) 14:35, 27 March 2012 (UTC)

Edit war?

I tried to follow all the edits over the last couple of months, but got horribly lost. Are you guys just cherry-picking individual (different!) papers to try and support some viewpoint that you're emotionally attached to? Clearly some people can't stand any hint that VY CMa might not be the largest star, and clearly some people are out to prove otherwise. If there isn't some relatively recent relatively well-supported compromise number, then at least quote the range of likely possibilities (which is huge!) and leave readers with an accurate understanding of the uncertainties. Lithopsian (talk) 16:31, 5 July 2012 (UTC)

Contesting a "[citation needed]"

Why the "[citation needed]" after the paragraph giving the comparison of the star's size on a scale where the Earth is 1 cm? It's an extremely trivial calculation that follows directly from information already provided earlier. In my opinion, a citation for such a trivial deduction is definitely NOT needed.

Actually, that entire paragraph qualifies as Original Research and should be removed. Tarl.Neustaedter (talk) 18:40, 11 July 2012 (UTC)

Size

Regarding the size calculation... assuming a solar radius of 6.96 x10^8 meters, 1800 to 2100 solar radii would be roughly 777 to 908 million miles. Given that Saturns orbit varies between 838 and 939 miles, the edge of the star could be, at times, beyond the orbit of Saturn. Xlation 18:56, 29 November 2006 (UTC)=

If we assume the upper limit, that is. And there are still controversies regarding the size of VY Canis Majoris. It might not even be as big as we think it is. Micasta (talk) 02:00, 8 March 2009 (UTC)

Okay, solar radius = 6.955 x 10⁸ m. 1800 to 2100 solar radii = 1.252 x 10¹² to 1.461 x 10¹². Diameter = 2.504 x 10¹² to 2.921 x 10¹² m. Micasta (talk) 16:16, 18 March 2009 (UTC)

"It would take over 7,000,000,000,000,000 (7 quadrillion) Earths to fill the volume of VY Canis Majoris.[citation needed]" Now why is there the unfamous "citation needed"? Using the wiki links to Solar radius (6.955*10^8m) and Earth (Volume=1.083*10^21m^3) and the volume of the sphere (4R^3*pi/3) everyone can calculate that it'd be about 7.6*10^15 times Earth volume, if the VY CMa were spherical (which it probably isn't, though it probably also doesn't matter much for the magnitude of the ratio). (Of course now someone can say "original research" or whatever that slogan is. But then I'd loose my last faith in secondary school science education). Hoemaco (talk) 19:49, 12 June 2009 (UTC)

I suggest changing the intro, which currently states, in part that certain experts "think that VY Canis Majoris is smaller: merely 600 times the size of the Sun." This reads as saying that the star is merely 600 times the size of the sun. But based on other data in the article, it is much, much larger than that, and the "600 times" figure must be referring merely to radius which, of course, is not overall "size."

I will point out a different issue - the current page reads "It is 1800–2200 solar radii (6.2–10.2 astronomical units) in radius". Those numbers are not consistent with each other. If the number in question is 1800-2200 solar radii, the second range should be 8.2 - 10.2 AU. I suspect it's just a typo. — Preceding unsigned comment added by 129.79.155.239 (talk) 15:35, 10 July 2012 (UTC)

The 6.2 may be a typo for 8.2, but equally likely it was typed along with a different estimate of the size. There has been a mass of edits over the last couple of months with different people quoting results from different papers as if they were handed down on stone slabs from heaven. The 600 refers to the lowest result found by a recent paper (Massey, 2006). Whether you describe the size in solar diameters or solar radii the number would be the same. You cannot state with any certainty that the size is "much, much larger than that" (unless you've taken a trip there recently?), although most estimates are two to three times that size and the most recent referenced paper quotes 1420. Currently the article is totally foo-bar'd, with at least three completely contradictory sizes listed, only one of them with a citation so far as I can tell (although I recognise the other results as numbers that have been published in papers at one time or another in the past 30 years). Also, at 1420 times the size of the sun it would not be "the largest known star" although almost certainly one of just a handful in the galaxy in that size range. Lithopsian (talk) 19:39, 10 July 2012 (UTC)

Is your 19 May version about right? Looking at the history of this page, it appears it is a frequent target for vandalism, and we need to heavily monitor (and revert) vandalism efforts. Perhaps request semi-protection for this page to prevent anonymous vandals. We can revert to the 17 May version and carefully examine every edit that goes in from here forward. Tarl.Neustaedter (talk) 05:20, 11 July 2012 (UTC)

I don't think the current version is much worse than the May 19th version, possibly even a little better. Many of the edits have cancelled themselves out. It does need some sensible tidying though. I'll give that a go and keep an eye on it for the next few weeks to see if it needs more protection. Lithopsian (talk) 21:10, 11 July 2012 (UTC)

Sounds good. I'll keep this on my permanent watchlist, and move towards semi-protection if it continues to have problems. Tarl.Neustaedter (talk) 23:44, 11 July 2012 (UTC)

WHat is teh "VY" ?

The name of this star is VY Canis Majoris. What are those two letters? I looked at the Star designation wiki article but it had nothing. I think it odd that I have to dig deeper than that to find out who stars are named. Can someone help me here? Nick Beeson (talk) 17:30, 31 May 2012 (UTC)

The designation "VY" (specifically, using two latin letters) indicates it is a variable star. See Variable star designation. — Preceding unsigned comment added by Tarlneustaedter (talk • contribs) 02:43, 23 July 2012 (UTC)

concurrency question

I'm not very well informed on how astronomists usually interpret a sentence such as "This star is likely to undergo a hypernova stage by 3200." in combination with the statements that it is 5k lightyears away, but would that mean that it actually probably underwent a hypernova around -1800 and that we will see this event in about 3200, or that it will undergo a hypernova around 3200 and that we will see this event around 8200?

Could somebody with more knowledge of the subject please clarify this a bit in the article?

I would guess that the correct interpretation is that the hypernova "really" happened ~1800 BCE and that we would observe it in 3200, since the information used by astronomers to make these estimations is ~5000 years old. However, there's always the possibility that these same astronomers already accounted for the travel time and believe that the star has already novaed...

--72.150.43.254 (talk) 04:42, 11 January 2008 (UTC)

We always use our local frame when talking about these things, as we are working from observational astronomy; if we are talking about the star's local frame of reference then it will always be explicitly stated. Sometimes the star's frame will be used when dealing with theoretical models, but again, this is normally explicitly stated if that is the case. Ageotas (talk) 02:09, 16 October 2012 (UTC)

Actual size

VY CMa is the largest known star discovered to date. Because several sources have stated that this is the largest star found to date. And it's between 1800~2200. Therefore it would still be bigger than VV Cephei A.

http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question21.html

"VY Canis Majoris show that it has a size between 600 and 2100 tims the size of our Sun!"

http://www.universetoday.com/13507/what-is-the-biggest-star-in-the-universe/ http://arxiv.org/abs/astro-ph?papernum=0610433

Rackshea (talk) 09:44, 22 July 2012 (UTC)

A couple of things. First, if you're going to make an edit, don't just change a number you don't like to one that you prefer without changing the citation also. Otherwise, even if I don't come along and revert it immediately, someone will come along eventually and see that the cited journal says something else and change your number. Ideally, change all the associated starbox data so it isn't quoting something that is totally contradicted by the other parameters. Also ideally, don't pick some paper from ten years ago when there are two or three newer ones.

Second, don't quote some tabloid webpage and claim that what it says is "fact". Half the web pages about this star claim it is the biggest because Wikipedia claims it is the biggest. Give it six months and see how many pages claim something else is the biggest if we change it here. From the two pages you give, one of them can't even spell the name of the star correctly, so I'd be wary of anything else it says. The other mis-quotes a specific paper about VY CMa, takes what the paper gives as the upper end of the likely size range, prefaces it with the word "over" for extra effect, ignores the lower end (just 600) and offers that as proof that this is the largest star. That paper itself is from six years ago, merely describes previous work, and has been superceded by new distance, temperature and luminosity measurements.

I am open to a variety of ways of describing the size of this star. The value 1420 edited in by Katydidit is from the most recent research I'm aware of, and which fully acknowledges earlier works giving both high and lower figures. There is also a paper from 2010 (http://arxiv.org/abs/1010.5369) which gives a slightly larger size and perhaps should be referenced. However if the consensus is that people would rather quote a wide range of (still relatively recent) older published values, and there is a WIDE range, then so be it. Just don't pick out the biggest number you can Google up and stick it in there with even bothering to change the reference. Lithopsian (talk) —Preceding undated comment added 13:39, 22 July 2012 (UTC)

Can somebody link me to the relevant research that shows that this star's radius is smaller than previously thought? 216.246.130.20 (talk) 01:31, 3 October 2012 (UTC)

References are linked in the article. If they aren't then kick up a fuss. Sometimes citations accidentally link the wrong article or misunderstand the findings of a paper. Doubt everything, double-check :) Lithopsian (talk) 13:53, 2 November 2012 (UTC)

I reverted an edit (November 2nd 2012)

I thought this reversion deserved a fuller reply than I can fit in the little edit change box since it seemed to be a good faith edit on a relevant topic. Possibly we should be making some statement about the fame of VY CMa and the current status as not quite the largest known star. I reverted the added text partly because we already have a section about the size of the star and don't need another one, partly because the information is a self-fulfilling prophecy. VY CMa is famous because Wikipedia says it is famous. There is a brief flurry of press releases and news stories when certain researchers found VY CMa to be one of the largest known stars, but it was primarily Wikipedia that put that information permanently in the public domain and made the star a household name. Probably 90% of the websites out there carrying this information just copy it from Wikipedia. Note that I said "one of the largest known stars": the margin of error on the sizes of all the contenders for this title means they are essentially the same size and we really don't have a clue which is the largest. We just pick one that happened to randomly end up with the largest number at any particular time. Very often this will be a "newcomer" precisely because the margin of error is larger with lesser known stars and one or other of them is going to end up looking very big. Later it will be downgraded a little (or a lot!) just as VY CMa has been.

So maybe you can add something about VY CMa being used in many scale comparisons, perhaps note that for several years it was widely known as the largest star. Make sure that you don't repeat information that is already in the article. Don't just state your own knowledge picked up from your friends or other websites. Someone comes along nearly every week and changes Wikipedia to state that VY CMa is the largest star, simply because they *know* it is, but that isn't really good enough unless you've actually been there with a tape measure. It is interesting to note the flurry of websites now listing NML Cygni as the largest star after it was left at the top of the Wikipedia largest star list more or less by default a few months ago. Nothing has really changed, there are still half a dozen stars all more or less the same size within the margins of error, and more or less at the theoretical limits for the size of a red supergiant. Lithopsian (talk) 14:05, 2 November 2012 (UTC)

Largest known star, really???

Possibly, though, I may state this. Lots of websites are still saying VY CMa as largest although it left the throne almost two years ago. Sheer enough to say these people do not update their data. And lots of them are still claiming VY CMa is the largest just because it has a "Major" in its name. Presumably though this word don't really make any sense to its size, it just states that its in Canis Major constellation. And now, it was dethroned by NML Cygni just a year ago and now Westerlund 1-26 already took the place today, it is still a bit floppy to say VY CMa as largest. Those people may be so pleased to this star because of its huge size of 2,100 solar radii, but even though it still retains that size with no revision happened it may still come 2nd with Westerlund 1-26 at 2,544 solar radii.

But still, two years ago when this star was still at the tips of the list, some people have wrong information about VY CMa. Some say it was 2,600 solar radii. Others say it was "only" a billion times bigger than the Sun, although computing the 2,100 solar radii figure in comparison to the Sun on Google Calculator gives you 9.261 billion times bigger than the Sun. Some say it was only 5,000 years old! And some say it may come hypernova within the next thousand years. How can these people get their reliable info? Such of these are so extraordinary, yet some are misconceptions. And now it has been revised down to 1,420 solar radii (with corresponding volume 2.86 billion × Sun), still some of them persist those old news.

It's great that I've seen lots of websites now reporting Westerlund 1-26 as largest, although its size was uncertain. Man discovers new everyday, maybe we see the true largest star in the universe someday. ==Johndric Valdez (talk) 13:53, 25 September 2013 (UTC)==

Problem with mass estimate?

It says on the last sentence in "Nature" that "it would have been an O star with a mass of 15 to 35 M☉." The estimate of the mass is 17 M☉. How can it be that a star of initially 15 M☉ became 17 M☉? Does it gain mass? It is supposed to lose mass. Someone must change this. Johndric Valdez (talk) 03:50, 1 May 2014 (UTC)

No contradiction. It's estimated mass is listed as 17 ± 8. Meaning somewhere between 9 and 25 solar masses. It probably started with 15 to 35, and has blown away somewhere from 6 to 10 solar masses. Tarl.Neustaedter (talk) 04:47, 1 May 2014 (UTC)

Edit request from Heliumsingh5000, 15 July 2011

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In the following given data in the article

" Size

University of Minnesota professor Roberta M. Humphreys estimates the radius of VY CMa at 1,800 to 2,100 solar radii.[9] To illustrate, if Earth's Sun were replaced by VY Canis Majoris, its radius might extend beyond the orbit of Saturn (about 9 AU). Assuming the upper size limit of 2100 solar radii, light would take more than 2.7 hours to travel around the star's circumference, compared to 14.5 seconds for the Sun. It would take 7×1015 Earths to fill the volume of VY Canis Majoris.

"

It should be noted that the time required for the light to travel the circumference of the star is around 8 hours as opposed to the given 2.7 hours

we can calculate according to the given radius of the star

Circumfrence = 2*pi*r = 2 * 3.1428527 * (2100*695,500) KM = 9,180,600,000 KM

Speed of light = 300000 KM/Sec

therefore time taken for a complete circumference =

9,180,600,000/300000 Sec = 30 602 sec = 8.50055556 hours

Heliumsingh5000 (talk) 11:40, 15 July 2011 (UTC)

Article is no longer protected so you may edit it yourself now. Jnorton7558 (talk) 00:03, 17 July 2011 (UTC)

I changed it to 8.5 Bhny (talk) 00:10, 30 September 2011 (UTC)

Density

Some notes on the density would be nice, for example, is it denser than water? Or is it closer to air? —Preceding unsigned comment added by 213.100.13.135 (talk) 23:37, 3 December 2009 (UTC)

The text now says “the star is a hundred thousand times less dense than the atmosphere of the Earth”, presumably satisfying the previous request in this ‘Density’ §. But please could there be an explanation of how fusion is happening at all at anything like that de minimis density? Or is there a ‘small’ dense centre, most of the rest of the star actually being inactive slightly-warm hydrogen gas? A large hot planet with a big atmosphere, as it were. I don’t know: these are questions. Of course it might be that there are competing hypotheses: please could the most plausible be summarised? JDAWiseman (talk) 18:58, 24 January 2015 (UTC)

@JDAWiseman: Basically the core still is pretty dense. The star is roughly the size of the orbit of Saturn, so the core still is stupendously big Tetra quark ^(talk) 19:12, 24 January 2015 (UTC)

The mass is given as 17 ± 8 ☉. If almost all the mass is in the core, and if it has the same density as the sun, then the core would have a linear size at most 25^⅓ ≈ 2.9× the sun. If the core is much less dense than the sun, then the core could be “stupendously big”. But in that case please could the article say how much less dense is the core, at least in theory, and how fusion still manages to happen. JDAWiseman (talk) 20:32, 24 January 2015 (UTC)

Extra, from Atmosphere of Jupiter: “In scientific literature, the 1 bar pressure level is usually chosen as a zero point for altitudes”. If that same standard were used for a star, this star would be much much smaller. If the standard were something to do with fusion, my question stands. JDAWiseman (talk) 14:44, 25 January 2015 (UTC)

A red supergiant star is not a gas giant planet. Any conventions that apply to one may not apply to the other. In this case they don't apply. Stellar sizes are typically defined wrt optical density. Lithopsian (talk) 14:57, 25 January 2015 (UTC)

I’m a non-expert reader, who was really puzzled by the idea that the diameter of the star extends to gas of almost zero density. Now I’ve learnt that “Stellar sizes are typically defined wrt optical density”. Please could the article include two generic sentences about this, and then another two sentences specific to this star. It might also be worth saying something like “if the diameter were measured as for a gas planet, that to the latitude with atmospheric pressure 1 bar, the radius would be …”, both in km and relative to the orbit of mercury.

For emphasis: I’m a puzzled reader, not an expert. In some sense, I am the target audience. JDAWiseman (talk) 21:57, 25 January 2015 (UTC)

Red supergiants have a core that is denser and hotter than a star such as the sun, although not necessarily fusing at all and quite often degenerate. They may be fusing helium or even heavier elements in the core at temperatures far higher than the sun, or they may be shell burning, depending on the exact stage of their evolution. The only thing that is vastly inflated is the outer, non-fusing, envelope of the star. Lithopsian (talk) 14:57, 25 January 2015 (UTC)

If both “hotter” and “not … fusing”, then I am much more puzzled than I previously estimated. JDAWiseman (talk) 21:57, 25 January 2015 (UTC)

Some numbers to toy with. The "core" of a red supergiant, (ie. the portion completely devoid of hydrogen) is typically a size of the order of the sun, containing something like a third of the mass, with a density anything from ten to several thousand times the density of the sun's core. Lithopsian (talk) 23:09, 25 January 2015 (UTC)

Fabulous! Please could somebody expert (translation: not me) put that in the article.

However, there is an arithmetic concern. If VY’s core is the size of the sun, and a large multiple of the density of the sun’s core, might it be more than a “third of the mass” of the sun? JDAWiseman (talk) 23:15, 25 January 2015 (UTC)

Later, on re-reading, I realised that Lithopsian presumably meant a third of the mass of VY Canis Majoris? A third of ‘17 ± 8’ is 3⅔ to 8⅓ M_☉. That better fits the massive density, but still not quite as much as “ten to several thousand times the density of the sun's core”. JDAWiseman (talk) 22:48, 26 January 2015 (UTC)

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Semi-protected edit request on 30 June 2020

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Is this new luminosity of 178,000 L_☉ for VY CMa true? I think it is not accurate since the Wittkowski luminosity of 270,000 L_☉ for VY CMa is considered a very well-measured luminosity. I think we should at least re-add the Wittkowski L back in the starbox. 2A01:E0A:47A:F100:7107:8443:684A:D6EB (talk) 19:57, 30 June 2020 (UTC)

Why shouldn't it be "true"? Times move on. The new calculation uses more recent photometry at more wavelengths to estimate the bolometric flux, combined with Gaia DR2 parallaxes. In the case of VY CMa, the Gaia parallax is not useful so the same maser-based distance as Wittkowski et al. (2012) is used. Hard to disagree with any of it. Lithopsian (talk) 20:36, 30 June 2020 (UTC)

Ok but I think since the Wittkowski Luminosity of VY CMa is still widely accepted sinec it is well measured and VY CMa is still referred as one of most luminous red supergiants as of now, we should keep it in the starbox by just comparing with the new luminosity of 178,000 L_☉. 2A01:E0A:47A:F100:7107:8443:684A:D6EB (talk) 20:41, 30 June 2020 (UTC)

Not done for now: please establish a consensus for this alteration before using the {{edit semi-protected}} template. ~ Amkgp 💬 07:31, 1 July 2020 (UTC)

Alcolea et all

Referring to the notes & caveats section, where is this Alcolea et all?PNSMurthy (talk) 02:14, 15 July 2020 (UTC)

Presumably ref #55. Lithopsian (talk) 10:36, 15 July 2020 (UTC)

ThanksPNSMurthy (talk) 06:14, 26 July 2020 (UTC)

2,000 solar radii estimate

This is What I was talking about At The Talk page for Lithopsian. It is about the 2,000 solar radii estimate. Should it be added in the starbox or is the average estimate of 2,000 solar radii Inaccurate? --THE COLOSSAL GALAXY NAMED IC1101 (talk) 06:02, 26 July 2020 (UTC)

De beck et all and Wittowiski et all, both much more recent estimates than Humphreys et all, give much smaller sizes. We don't need to stick beside old and outdated estimates when new estimates provide much more accurate estimates.PNSMurthy (talk) 06:10, 26 July 2020 (UTC)

I am talking not about the 1,800-2,100 solar radii. I am talking about the average estimate of 2,000 solar radii in a 2013 paper. The sockpuppet named Joey is also a fan of VY Canis Majoris. He has accepted Stephenson 2-18 as the largest star But still, He Continues to put VY Canis Majoris at 2,000 or 2,100 solar radii... --THE COLOSSAL GALAXY NAMED IC1101 (talk) 07:32, 26 July 2020 (UTC)

Semi-protected edit request on 13 July 2020

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124.180.0.37 (talk) 05:39, 13 July 2020 (UTC)

Extended content

| class = M2.5–M5<ref name="Wittkowski_vlti"/> {{nowrap|(M2.5<ref name=massey2006/> - M5e Ia<ref name="LipscyJura2005"/>)}}

| radius                 = {{val|2,600|140|fmt=commas}}<ref name=Wittkowski_vlti/>

... derived an average size of {{solar radius|2,000}}.<ref name=kaminski/>

Another paper was published at size estimate of {{solar radius|2,600}} instead of {{solar radius|1,420}}.<ref name=whitehot/>

Refactored to show changes only. Matt Fitzpatrick (talk) 10:02, 13 July 2020 (UTC)

Question: You added a ref tag for a new source, but no citation to go with it. Could you please provide the citation? Matt Fitzpatrick (talk) 10:02, 13 July 2020 (UTC)

Not done: please provide reliable sources that support the change you want to be made. Matt Fitzpatrick (talk) 04:45, 28 July 2020 (UTC)

Second RSG phase

There's a paper (Humphreys et all 2016) that suggest VY Cma is in a second RSG phase. Can it be added?PNSMurthy (talk) 05:15, 30 July 2020 (UTC)

De Beck et all

Doesn't De Beck et all (the paper which gives 1,183 Rsol for NML Cygn) give around 1,600 Rsol for VY Cma? Should it be added in the starbox?PNSMurthy (talk) 06:16, 26 July 2020 (UTC) - The paper in question is here.PNSMurthy (talk) 06:18, 26 July 2020 (UTC)

With T_eff = 3605 and 428303 L_☉, we get 1,678 R_☉, so yes. What makes their research better than Wittkowski et al, which gives 1490 R_☉? Primefac (talk) 16:54, 26 July 2020 (UTC)

There's nothing better about it. I just wanted to know if we could include it in the starbox. We shouldn't ignore research, should we?PNSMurthy (talk) 23:02, 26 July 2020 (UTC)

Erh What about that 600 solar radii estimate? we are Ignoring it...--THE COLOSSAL GALAXY NAMED IC1101 (talk) 05:27, 27 July 2020 (UTC)

Goes by wholly different assumptions. See my second edit request in the talk list of largest stars. Me and a few other users discussed that very estimate. PNSMurthy (talk) 05:30, 27 July 2020 (UTC)

The starbox should give the best/consensus value, sometimes more than one value, but not a list of historical values that are clearly superceded. Historical or non-consensus values can be discussed in the body of the article if they are notable or add useful context. Lithopsian (talk) 09:56, 27 July 2020 (UTC)

Very well, will do later.PNSMurthy (talk) 10:26, 27 July 2020 (UTC)

The colossal galaxy named IC 1101the 600 solar radii seems way too small for a red hypergiant with a really high mass loss rate. Be suspicious of anything under 1,000 solar radii for VY Cma.JayKayXD (talk) 16:02, 7 August 2020 (UTC)

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Radius

I posted this on another article (list of largest stars) but i'll post it here too. If it says that in 2013 VY Cma was proven to be 2069 Rsol, but if it was so, the page wouldn't say that it was 1420 Rsol in 2020. Explain pls--WRMetacat108 (talk) 14:09, 17 November 2020 (UTC)

"Proven" may be the wrong word, all these values are simply different astronomers' best guesses. Which one should go in the starbox as the preferred value for Wikipedia is not always obvious. In this case it is clearly controversial and this may be the time and place to discuss it.

The 1,420 R_☉ value is from a 2012 paper dedicated to deriving the best possible values for the physical properties of VY CMa at that time based on new observations. I have seen nothing that fundamentally improves on this since. The value was based on an angular diameter and a distance, neither of which are fundamentally in dispute. It went on to derive a temperature of 3,490 K, consistent with widely-accepted temperature scales for red supergiants.

A paper in 2013 published a radius of 2,069 R_☉. This was based on an obsolete temperature from 1996 and a luminosity plucked out of nowhere. These were used to calculate the radius, which was quite large because the temperature was lower than any astronomer would give today. Or perhaps the radius was plucked out of nowhere and used to calculate the luminosity, the paper isn't exactly clear. Curiously, the luminosity is exactly the value derived in the paper from the previous year which gave a radius of 1,420 R_☉. It wasn't in Wikipedia because it was not a new derivation, not intended to be so, and was based on a random temperature from the last century for some reason. The value 2,069 R_☉ was then repeated in a 2020 paper (in cm), which in Wikipedia terms counts as a secondary reference and gives weight to the idea that it is an accepted consensus value among astronomers. Whether that is now the consensus radius among astronomers or not is arguable, but scientifically it is still bogus. Discuss.

P.S. I'm changing the temperature regardless of this discussion. It is thoroughly obsolete and needs to go. No galactic red supergiants are considered to have temperatures that low. Lithopsian (talk) 16:27, 17 November 2020 (UTC)

Humphreys et al. 2020

https://arxiv.org/abs/2012.08550 In a very recent paper by Roberta M. Humphreys and more, it is stated, "Non-radial pulsation is a possibility, but how would one separate that from large active regions on a star with a radius of ≈ 7 AU?". It is not stated how this radius is reached, and translates to roughly 1,505 R_☉. I doubt this is reliable enough, as it isn't referred to in the paper anywhere else than what I quoted. Any other opinions? Faren29 (talk) 23:09, 22 December 2020 (UTC)

The traditional 1,420 R_☉ radius rounds to 7 AU. For the purposes of this paper, no more accuracy is really needed. Almost any radius published this century can be considered ≈7 AU, give or take a couple. Lithopsian (talk) 15:34, 23 December 2020 (UTC)

Do you think that VY CMa should be moved down to the radius given by Wittkowski et al. 2012. This current radius, seems like it could potentially be a consensus value, but 1,420 R_☉ may be more accurate. Faren29 (talk) 18:43, 24 December 2020 (UTC)

Location of VY CMa

The map image labelled "Location of VY CMa" suggests the location of the object in the image is circled. There are a number of problems with this method of identifying items in images, that occurs frequently throughout Wikipedia, that ideally could be addressed (?). At best, this method is confusing: a. the red circle is so small, I didn't even see it initially, and if I hadn't re-read the image caption, I wouldn't have known. b. the red circle is not labelled as VY CMa so it is not even obvious that it is the object in question, yet other items on the map are labelled. c. there are four other black circles in the image. d. When the user enlarges the image, the red target circle disappears, making the location of the target object impossible to find, and ambiguous because of the four black circles. Fundamentally: Why do image pointers disappear in Wiki pages when the image is enlarged? Captions and labelling could be improved in this article. SquashEngineer (talk) 14:07, 10 August 2021 (UTC)

Repetition

The Size and Largest star sections contains several sentences quite similar to each other, which means there is quite a bit of repetition. I propose that the sections should be merged somehow. nussun (talk) 07:52, 29 October 2021 (UTC)