Talk:Eta Carinae

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Variability[edit]

"One remarkable aspect of Eta Carinae is its changing brightness. When it was first catalogued in 1677 by Edmond Halley, it was of the 4th magnitude, but later it brightened, reaching its greatest brightness in April 1843"

Wording[edit]

I don't know how to word it, but could the 2nd sentence be changed without getting too detailed, to indicate its varying brightness so readers don't think it only brightened from 1677 to 1843. Also, is it too fine a point to say "greatest *recorded* brightness in April 1843"?

Sols not right word[edit]

  • "Sols" isn't a commonly used term among astronomers. We would be more likely to say "4 million times brighter than the Sun" or "4 million solar luminosities" or "4 million L(with a little sun symbol subscript)". Just a little nitpick. Also Eta Car is classified as a luminous blue variable, but there isn't an article for that yet. Maybe I should start it. :) - Etacar11 15:12, 20 May 2005 (UTC)

Binary star?[edit]

The article currently says:

Recent observations seem to indicate that eta Carinae is actually a binary star, the two stars orbiting each other with a period of around 5.5 years.

Says who? Do we have a reference? Let's find out who made these observations and change this to active voice. --Doradus 16:24, Jun 1, 2005 (UTC)

It's an open issue but I think most astronomers who study Eta Car are leaning towards binary. Here's some references from ADS:
--Etacar11 16:57, 1 Jun 2005 (UTC)

Can you place this in the article? I was curious to read the references, and when the discovery was made. Although it is not difficult to find the references here, I think the article would be better served by having the references within it. Thanks. —Preceding unsigned comment added by 66.110.243.48 (talk) 20:10, 19 May 2009 (UTC)


I'm a bit surprised at that, is no-one aware of http://www3.mpifr-bonn.mpg.de/div/ir-interferometry/gallery/etacar_front.html f.e.? That's a -lot- earlier than 2005 and there are later observations by HST too. — Preceding unsigned comment added by 2001:A60:F000:67:0:0:0:2 (talk) 18:45, 30 December 2012 (UTC)

The objects resolved in that paper, and still visible today, are not companion stars. They are just lumps of gas and dust. The companion is much closer, in an eccentric orbit between about 5 AU and 15 AU if I remember right. Lithopsian (talk) 20:45, 30 December 2012 (UTC)

Eta Carina Nebula, Keyhole Nebula?[edit]

I understood the Keyhole nebula is a formation with the Eta Carina Nebula, fairly small and near the Eta Carina Star - small enough that changes in area gas and dust distribution had changed the view of the Keyhole nebula because it is illuminated by nearby stars and the shadows have moved in the view since Herschel's day.

  • You are right, the Keyhole Nebula is part of the Eta Carinae Nebula, not another name for the whole thing. It should be clarified in the article. --Etacar11 18:56, 18 August 2005 (UTC)


Clarification: The Carinae Nebula is a few degees across and includes many stars, nebulae, one of which is the Keyhole Nebula. The 'Eta Carina Nebula', i.e. ejecta thrown out of Eta Carinae and excited by same, is the Homunculus, a bipolar, or hourglass-shaped dusty nebulosity thought to originate in the 1840s and is at least 12 solar masses. Internal to the Homunculus is the Little Homunculus, an ionized hourglass-shaped nebulosity associated with the 1890's lesser event.

Typo[edit]

It said the sun has a 10 million year life span. It is billions. Corrected. :) lol Also, in reality the star is 8,000 light years away. Every where I have read about Eta says the event happened in 1841. We saw the light from the explosion in 1841. The true instance happened 8,000 years earlier. Sooooo, civilization was on the brink of coming together when this truely happened. Just thought I would point that out. I would put it into the article but I don't know how to word it properly. Since I haven't read that anywhere, I'm not sure if people would understand. It makes sense though, right? 8,000 lights years! It could be possible that the star has already blown. It could have blown 400 years after and we wouldn't know for another 200. 1841 was almost 200 years ago + 200 years into the future to equal 400 years. The intial explosion would have happened in 6041 b.c. Am I making sense?? Scientists are saying they are waiting for eta to blow like it is some kind of nearby volcano. Why the contradictions?? It could have blown in 1 a.d. and we wouldn't know, even with the most powerful telescopes, until another 6,000 years!!!! Gimme some feedback, cause' I am starting to confuse myself. If I am over looking something point it out to me pleeeease.--Guitarist6987876 23:31, 3 October 2005 (UTC)

  • It did not say the sun has a 10 million year life span. It says 10,000 million, which is equivalent to 10 billion. And a star like Eta Car has a lifetime on the order of 1 million years. --Etacar11 02:16, 4 October 2005 (UTC)

I caught that. I see the 10,000 million now. I actually didn't mean to change the 1 million year lifespan for eta. I just don't want some kid going around saying the Sun in 5 million years old because they didn't see the 10,000 part. I overlooked it, so I am sure other people will. I left the 10,000 million but I added 10 billion beside it so people who don't understand will have a clearer picture.--Guitarist6987876 02:30, 4 October 2005 (UTC)

Unfortunately, the expression billion is ambiguous, outside the US, and regions of US-influenced language. Its generally understood to be one thousand millions in the US, but some UK folk, and much of the rest of the world will understand it to be one million millions. There's a good explanation of Long and short scales and why its better to avoid using terms like billion when writing for general audiences. I'm not going to revert the edit, but I'd vote to leave it as "thousand million" and not "billion". --Raduga 17:38, 2 November 2005 (UTC)
From our frame of reference Eta Carinae erupted in the year 1841. It is perfectly right to say so.--Jyril 10:03, 4 October 2005 (UTC)

True. Technically though, false! --Guitarist6987876 14:22, 4 October 2005 (UTC)

What you mean by "technically"? If we saw Eta Carinae exploding now, the explosion occurs now even if it exploded 8000 years ago from Eta Carinae's (or from the remaining black hole's or whatever's) reference frame.--Jyril 17:57, 4 October 2005 (UTC)

So you are saying that if we could look at the light from the big bang, even though it happened 13.7 billion years ago, that the big bang is happeneing now?? It is the same concept! --Guitarist6987876 23:06, 4 October 2005 (UTC)

In a way, yes. We would see the Big Bang happening to them now. In a sense, Big Bang is an ongoing event. Some GR expert may explain better or correct me if I'm wrong.--Jyril 12:24, 14 October 2005 (UTC)
We do see the microwave background radiation, which doesn't come from the big bang itself (13.7 billion years ago) but from so close (13.7 billion - 300 000, that is 13.6997 billion years ago) that it makes little difference from our perspective. So, yes, that background is happening now, but it's also happening now everywhere else, including places billions of light years from us. Or would be if the concept of now billions of years away made any kind of common sense. Confusing, eh? --King Hildebrand 17:27, 29 August 2007 (UTC)

The Eta Carinae eruption did not occur in 6041 BC. It is not exactly 8000 light-years, but approximately 7500 to 8000 light-years. AstroHurricane001 17:31, 29 October 2006 (UTC)

Possible Eta Carinae Hypernova[edit]

I have added few lines about the possible Eta Carinae Hypernova and it's effect on Earth. I would welcome comments.

Siddiqui 21:54, 16 January 2006 (UTC)

  • What I've been given to understand (I've worked for someone who does a lot of Eta Car observation) is that we aren't in much danger in ANY case if the radiation isn't beamed in our direction (hypernovae are thought to usually be highly beamed, I think) but it could be devastating if it was... --Etacar11 22:11, 16 January 2006 (UTC)
I hope that earth is not in the direction of radiation burst. Within 24 hours whole earth will be exposed to potentially lethal radiation. The HyperNova are very unpredicatable and Eta Car may have erious implications for life on earth.
Siddiqui 17:03, 19 January 2006 (UTC)
If we go, we go. No point fretting over it.
88.110.88.75 17:15, 10 April 2006 (UTC)
Hypernova explosions are thought to travel at nearly the speed of light. Therefore, it would take about 8000 years after the explosion to reach Earth. Also, ther is a possibility that when a hypernova explodes, it just emmits a hollow sphere of radiation, with a few holes. Therefore, if it reaches Earth, it should be a wave. If you looked at Eta Carinae 8000 years after the explosion, you should see it continously brighten. It then expands into a bright ball. Soon, it explodes and the whole sky is lit up. The whole sky could reach mag. -50. Soon, the light could also emit heat and weaken the ozone layer. After the wave, some of the sun's radiation could penatrate the atmosphere and burn the sky. There could be another extinction. Note this is highly speculative and only has a 5% chance of occuring. Eta carinae probably won't explode for another 200 000 years. If it only creates a supernova, it would still reach about mag. -10, but the effects won't be as bad. Let's hope Eta Carinae holds its gas for a while. AstroHurricane001 17:43, 29 October 2006 (UTC)
The issue is if it exploded only a little after 8000 years ago, the explosion, bean or just plain blast, might be reaching us soon, and we wouldn't know until it's here. When talking about things that happen at such big distances often what people call "now" is actually the time in the past we are seeing now, not what we would find there if we somehow managed to travel there significantly faster than the speed of light. --TiagoTiago (talk) 02:48, 10 November 2011 (UTC)
Let's keep a sense of perspective. Eta Car is one of the closest and soonest future supernovae, but there are other and even closer candidates (e.g., Betelgeuse at 500 light years). One at 500 LY has probably exploded every few million years or less. Yet there haven't been mass extinctions anything like that often! Eta Car is extremely unlikely to cause one -- although even some modest environmental disruptions could, I suppose, cause a collapse of civilization for a few centuries. (I greatly doubt it, but that's a lot less than a mass extinction.)
BTW, the -50 magnitude is simply inaccurate. That would be the brightness as seen by an observer as close to the explosion as the Earth is to the Sun -- not a nice, safe 8000 LY. Jmacwiki (talk) 06:32, 12 January 2009 (UTC)

This doesn't sound very NPOV[edit]

I saw an edit that an IP just made [4], and it doesn't sound very NPOV, and it has no references. Although the content sounds believable, I'm not sure where the scource came from. Also, if the content is true, someone should add references and remove the bias. This new edit seems to promote oh! look at eta carinae! it's so more important than the other stars so pay attention to it now! It made it seem like Eta Carinae jumped from 5th to 1st on the most luminous stars list. If this actually happened, someone should put it on the list. If it's not true, it should be changed so that it is true, at least according to up to date information. AstroHurricane001 22:32, 10 November 2006 (UTC)

I just made a quick edit to the star's size. Recent reports say that it has expanded. I'll post the links tonight.

Table[edit]

The table takes up the entire page. I'm not sure how to fix it, otherwise I would. Darry2385 02:50, 30 April 2007 (UTC)

Apparent magnitude out of date?[edit]

There are two conflicting magnitudes listed in the article. It appears eta car has apparent magnitude around 5.1: AAVSO

Someone should mention that this explosion is mostly harmless because main burst will not hit Earth. Even by 7500 ly we would be toasted in direct hit. Source: [here] .

"Note that the lobes appear to be tilted away from us by about 40 degrees or so. That’s a good thing. When stars like Eta Carinae explode, they tend to shoot of beams of energy and matter that, at its distance of 7500 light years, could kill every living thing on Earth. But since it’s pointed away from us, all we’ll get is a spectacular light show."

How close to supernova?[edit]

This recent article claims that Eta Carinae will almost certainly go supernova in the next few centuries, whereas the article suggests it may be up to 1 million years from now. Which is more accurate? MOXFYRE (contrib) 15:30, 23 June 2007 (UTC)

The article presents a plausable argument but remember, it's promoting his book. GraL (talk) 12:12, 30 October 2008 (UTC)
The big unknowns to the equation are 1)just how old is the star and 2)what are the orbits and weights of the supposed two (or even three) stars of the system? The 1843 event, though, is highly suggestive of that Eta Carinae would be near its death-throes (too bad a final explosion, if it happens within the next few centuries, will not be visible from Europe or North America!) Strausszek (talk) 22:41, 21 July 2010 (UTC)
...but hopefully it will not fry us, right? Artem Karimov (talk) 14:43, 2 January 2011 (UTC)

proposed move/redirect[edit]

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section.

Hi. For some reason, this article keeps calling the star Eta Carinæ. So, I am suggesting a move to (or redirect from) this page. Please settle on a consensus, and indicate support or oppose suggestion below. Please include a reason, and a suggestion on what to do. Thanks. ~AH1(TCU) 18:53, 29 June 2007 (UTC)

  • I think that that should be a redirect, since no one is going to type that in on a keyboard. Leave the article itself where it is. My two cents. --Etacar11 19:26, 29 June 2007 (UTC)
There... I made the redirect Eta Carinæ. Use of the æ ligature in English is pretty inconsistent, so it probably makes sense to have a redirect. MOXFYRE (contrib) 19:52, 29 June 2007 (UTC)
I suggest either a move to the correct name, or the use of {{wrongtitle}}. Though there aren't actually any technical restrictions preventing us using the correct name... Modest Genius talk 15:12, 4 July 2007 (UTC)

The word should be written "Carinae". The "æ" is a typographical ligature, not a feature of the spelling (which has two letters; it's an ordinary Latin 1st declension genitive). See æ for details, noting "Both classical and present practice is to write the letters separately". I've corrected the typography in the article. Gdr 14:04, 5 July 2007 (UTC)

fair enough Modest Genius talk 22:05, 10 July 2007 (UTC)

The above discussion is preserved as an archive. Please do not modify it. Subsequent comments should be made in a new section.


Proposed merge[edit]

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section.
I also suggest we merge Homunculus Nebula into this, I've slapped merge tags on them both Modest Genius talk 15:23, 4 July 2007 (UTC)
Why? They are different things. --IanOsgood 19:13, 12 July 2007 (UTC)
I agree, they should not be merged. Merging doesn't seem appropriate here... the two articles cover different, but related astronomical bodies. They don't duplicate each other significantly, and the distinction between the topics is clear-cut. MOXFYRE (contrib) 13:47, 13 July 2007 (UTC)
Hmmm, perhaps it's clear to some, but Joe Public coming along and glancing at the articles will just see the same picture, and will get horribly confused; this is especially true if he reads the articles properly and finds two different things described. besides, it's rather difficult to have any understanding of the nebula without an understanding of the central star(s). It's not like putting it all on one page would be unnecessarily long or misleading - they're inextricably related. Would you advocate separate articles for HD 44179 and the Red Rectangle? The distinction is virtually identical to that between Eta Car and the Homonculus. Modest Genius talk 21:16, 18 July 2007 (UTC)
Acting as 'Joe Public'. Arrived here via today's Picture of the Day on the Main Page and via the Homonculus. Seeing Homonculus twice in succession seemed initially a bit naff. Would a label such as 'Eta Carina within the Homunculus Nebula' help? Vote to keep articles separate - other star images displayed within a nebula from a separate article Pistol Star. --Eddie | Talk 07:24, 20 August 2007 (UTC)

I Disagree beteween the merge becuase the articles are about different hypernovas it isnt a hypernova page where you can just chunk in some information if we merge it how can people tell beteween Eta Carinae and Homunculus Nebula. Ratesreal1 | Talk 08:16, 20 November 2007 (ETC)

I disagree with the disagreement. Merging might be reasonable, provided that the material is sparse, or the star and the nebula are inseparable. The difference between Eta Carinae and Homunculus Nebula can be told the reader by sectioning the article in f.ex. the section the star and the Homunculus Nebula, to reflect different research, and f.ex. physical processes to reflect theories of etas outburst and the formation of the nebula. Both topics might be separated by the text layout and the text content. Merging is probably a good thing. Said: Rursus 15:35, 22 June 2008 (UTC)

Uh, what? Eta Carinae is a star, and the Homonculus Nebula is a nebula around the star, caused by the star. Neither are hypernovae (which is an event not an object anyway), and people could tell the difference by the difference being explained in the article. The point I was trying to make was that it is impossible to explain the Homonculus without knowledge of the star, and thus they should be explained together, rather than in two places. Modest Genius talk 22:12, 21 November 2007 (UTC)

If I'm not entirely hallucinating, I believe I've heard Eta mentioned as a "hypernova" some time before (mayhap in the 1980ies), a notation that is probably quite obsolete considering new other "hypernovas" of a much more spectacular kind. As regards to Eta and Homunculus, I think their articles may profit from being merged. Said: Rursus 15:39, 22 June 2008 (UTC)
It might go hypernova at some point, yes. But it hasn't yet. Modest Genius talk 17:17, 22 June 2008 (UTC)

The above discussion is preserved as an archive. Please do not modify it. Subsequent comments should be made in a new section.


Is this a supermassive star?[edit]

The article "supermassive star" indicates that a star above 60 solar masses is widely believed to be impossible... --Phenylalanine (talk) 01:35, 26 June 2008 (UTC)

That article appears to be a bit of a mess, especially by conflating supermassive stars and supermassive black holes, which are on utterly different scales. The precise limit is unknown, but generally thought to be somewhere between 100 and 150 solar masses, and may depend on metallicity. Modest Genius talk 14:16, 26 June 2008 (UTC)

Foramen[edit]

This star also has the traditional name Foramen, which is Latin for "Opening".70.112.71.2 (talk) 22:27, 23 December 2008 (UTC)

If this is true then references are needed.-- B.D.Mills  (T, C) 03:53, 2 April 2009 (UTC)
Reference added, although I think it was a common error to confuse "anatomical" descriptions of old for real names. I'm not quite sure what a name is but I'm pretty sure that a real name must have some tradition of being used interchangeably with the common designation η Car, f.ex. being printed in an atlas, or written instead of "η Car" in an observation paper or some such. Before the Bayer designations, Flamsteed designations and catalogue numbers, the astronomers used long Latin descriptions in the old catalogues, f.ex. Quae hanc rursus comitatur ("that which accompanies on the opposite side") for ε CrB. Some of these descriptions could have been confused for real names. Rursus dixit. (mbork3!) 19:54, 20 September 2010 (UTC)

When was this minimum?[edit]

A "spectroscopic minimum" or "X-ray eclipse" appeared in the midsummer of 2003.

This is a very dubious time reference. Is this really an event for a southern star being described with northern-hemisphere seasons? The night sky can be seen all over the world, and thus it is quite inappropriate to use terrestrial seasons in this way, per MOS. -- B.D.Mills  (T, C) 01:28, 31 March 2009 (UTC)

AAVSO show no significant optical decrease throughout 2002-2004 [5]. This website shows a local minimum around July 2003, but a global minimum around January 2003; which one is referred to in the article is unclear. Not sure where the X ray data can be found. Modest Genius talk 23:27, 31 March 2009 (UTC)
Thanks. Have used the above to clarify the time reference. The (northern) summer reference for a southern star was a real howler of an error! What possible connection can earthly seasons have to events in the night sky? (Says Eta Carinae: "oh! It's going to be be summer in the northern hemisphere on this small planet thousands of light years away, several thousands of years from now, it must be a good time to have an x-ray minimum!") -- B.D.Mills  (T, C) 03:45, 2 April 2009 (UTC)
Are you sure this is what the text actually refers to though? The cited source is an Argentinian website, so there exists the possibility that whoever added it actually lives in the southern hemisphere and was referring to Jan 2003 Modest Genius talk 15:58, 2 April 2009 (UTC)
In the southern hemisphere the summer straddles year boundaries so "summer 2003" is ambiguous. A southern-hemisphere summer reference would be more likely to be given as "summer 2003-04" or "summer 2002-03". This is why I feel that it is more likely that the seasonal reference was in relation to the northern summer. To ensure accuracy, I have deleted the disputed time reference, leaving it as 2003 without being more specific. I do not believe this deletion impacts materially on the article as a whole.-- B.D.Mills  (T, C) 01:47, 3 April 2009 (UTC)

Faces in the future prospects photo?[edit]

Anyone else noticed patterns in the "future prospects" photo? It's the one like a Jackson Pollock painting - wikimedia link:

http://commons.wikimedia.org/wiki/File:Eta_Carinae_Nebula_1.jpg

I set is as my desktop, and on full screen I can see four spooky faces staring back at me.

I've tried to download the image, but all I get is an error page. Has it been manipulated? Shtove (talk) 21:43, 3 February 2011 (UTC)

Well, it has been manipulated, but only to better display the nebula, not to add 'spooky faces'. I have the feeling you're just seeing the (many) bubbles, and recognising a face pattern where none exists. The resizing your operating system is doing to put it on your desktop may well be making the bubbles more apparent. If you want the full size image, I suggest reading the bit on the image description page about opening very large images - that one is over 400MB. Modest Genius talk 23:12, 4 February 2011 (UTC)
Thanks.--Shtove (talk) 15:41, 8 February 2011 (UTC)

discrepancy on another page, plz hlp[edit]

on this page, http://en.wikipedia.org/wiki/Homunculus_Nebula#cite_note-2 , it says , "[T]he most massive star in the Eta Carinae multiple star system has less than 100 times the mass of the Sun." at the end of the section titled "Shape". . . and on this page, http://en.wikipedia.org/wiki/Eta_Carinae , at the end of the first paragraph of the section titled "Significance" it says, "The most massive star in the Eta Carinae multiple star system has more than 100 times the mass of the Sun." —Preceding unsigned comment added by 67.200.132.114 (talk) 21:16, 16 March 2011 (UTC)

Fixed— I found a reliable source (SEDS) that is quoted as "probably more than 100 Solar masses". There is some slight controversy here, as another source I found says "about 100 Solar masses". I figure SEDS is the most reliable source that I found. – PIE ( CLIMAX )  21:37, 20 February 2012 (UTC)

1000 years ago??[edit]

In the caption to the illustration in the section X-Ray Source it is stated that "The outer ring provides evidence of another large explosion that occurred over 1,000 years ago." Given that the star is more than 7500ly away, anything we can see is evidence of what happened more than 7500 years ago. Presumably what is meant is that the other large explosion happened 1000 years before the currently visible state of the star. Is this sort of unclarity an accepted way of speaking in astronomical circles, or should this be corrected. If so, is there a concise term to use in this sort of admittedly confusing situation? Hammerquill (talk) 02:48, 28 May 2012 (UTC)

All time-varying events in astronomy refer to the time of the event as observed on Earth, unless otherwise specified. This is normal and widely understood by anyone with a passing interest in the subject. Modest Genius talk 11:31, 28 May 2012 (UTC)

This article is way way out of date[edit]

Someone needs to update it to reflect research done in this century. Eta Carinae is conclusively a binary and the properties of the components are moderately well defined, so much of the data in the starbox has changed. I did the changes once, but my edits got backed out. Lithopsian (talk) 09:20, 11 June 2012 (UTC)

After examining the changes in detail, I have replaced what was undone. All my data was supported by references to recent peer-reviewed journals. Old citations were only removed if they were no longer referenced at any point in the article. I'd be quite happy to leave in older references to give some context, but Wikipedia complains if I do that. Article text was only changed when it conflicted with the latest data. I will be happy to clarify further if necessary, but don't see the point of going back to something that is just plain wrong. Much of the old data was not supported by any references at all, or was simply reporting numbers from other non-verified we pages. Lithopsian (talk) 13:25, 11 June 2012 (UTC)

Speed of shock waves from Eta Carinae[edit]

Under the section "X-Ray Source" it states: "4U 1037–60 (A 1044–59) is Eta Carinae. Three structures around Eta Carinae are thought to represent shock waves produced by matter rushing away from the superstar at supersonic speeds." (emphasis mine) The definition of supersonic is faster than the speed of sound. This seems wrong since I thought there is no sound in the vacuum of space. Is this meant to mean faster than 1207.5 kph (the speed of sound at sea level on Earth)? Is there an actual speed available? I'm not an astrophysicist so I don't feel qualified to get the science right. In fact, I could be totally wrong here. But it doesn't sound right and feel this needs to be written better.

SEKluth (talk) 03:26, 14 August 2012 (UTC)

They do indeed mean supersonic; these are shockwaves in gas nebulae, which is gas (albeit rather low pressure), not vacuum. Tarl.Neustaedter (talk) 21:58, 14 August 2012 (UTC)
However, don't assume that the speed of sound in this particular location is related in any way to the speed of sound in the Earth's atmosphere. The relevance of the term supersonic is that it exceeds the ability of the medium to propagate pressure changes, hence leading to shocks. In the context of a nebula this leads to, heating, radiation including x-rays, and the formation of particular structures quite different from non-supersonic winds. Lithopsian (talk) 13:58, 15 August 2012 (UTC)
So how does one even define the speed of sound in a gas with just a few molecules per m³? And what, approximately, is the value of that for an interstellar nebula? Since s.o.s. goes up with the material density, I would think the speed in such a rare gas would be near zero. Final question: is there a symbol like "c" for the speed of sound (in an implied medium)?
Dave Bowman - Discovery Won (talk) 09:32, 2 January 2013 (UTC)
This has been discussed to death in the Betelgeuse talk page, more than you'd ever want to know. The symbol c is sometimes used for the speed of sound. However this isn't common as it isn't a universal constant like the speed of light, rather a property of individual materials. Lithopsian (talk) 11:20, 2 January 2013 (UTC)
The isothermal sound speed c_s is given by c_s^2=\frac{P}{\rho}, where P is the (thermal) pressure and \rho the density. It varies by orders of magnitude between different regions of the ISM, because the pressure and density do, but as a rough estimate the range would be 0.1 to 100 km/s. Modest Genius talk 21:17, 2 January 2013 (UTC)

Surrounds section[edit]

Hey all, we gotta figure the best way of summarising its relationship with its surrounds. Hence I've added a bit to expand. My query was whether it was worth merging this article with the Homunculus nebula...? Casliber (talk · contribs) 23:43, 30 December 2012 (UTC)

Wasn't that already argued in 2007? See above, one of the gray-background sections saying "don't delete this earlier argument". Tarl.Neustaedter (talk) 04:39, 31 December 2012 (UTC)
aah I see. Ok, will wait to see how article expands then. Casliber (talk · contribs) 11:57, 2 January 2013 (UTC)
I still think merging would be a good idea, and that discussion was a long time ago. But I don't have time to work on it anyway. Modest Genius talk 21:19, 2 January 2013 (UTC)

Chinese Name 'the Second Star of Sea and Mountain'[edit]

I speak Chinese, and Hai Shan Er is translated literally as Sea Mountain Two. It makes no mention of a star. Of course, I'm no scholar of Chinese astronomical history, but I'm not entirely sure random words pop up in names for no reason. If, perchance, I'm incorrect and the words do change then ignore me by all means. If not, then '海山星二' would incorporate the star part of the English name; if that's not right, the English might as well be changed. Incidentally, I did try to look at the source of the name, but it was composed entirely of gibberish characters except for the parts written, predictably, in English. I'm relatively sure it's because a language pack failed to install correctly, but it might invalidate my argument for the Chinese name to be changed if it's written as on that site. — Preceding unsigned comment added by 114.25.202.157 (talk) 11:25, 15 April 2014 (UTC)