This is an archive of past discussions about Betelgeuse. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.
Someone gave me a news paper clipping (I don't know the paper, sorry) that claimed it was probable that Betelgeuse could supernova within the next year or two, is there any major consensus here or just some journalism, the same article said it could still be within millions of years88.111.136.247 (talk) 15:41, 22 January 2011 (UTC)
Yeah I saw that on the news too. Wondered why it came up now. The evidence cited by the sceintist in the news byte was the shrinking, but that is discussed in the article; there was no new news stuff. Casliber (talk·contribs) 19:38, 22 January 2011 (UTC)
So Should not someone give this fact(that the explosion is probable in next few years) in main page itself ? It is otherwise confusing as if they are talking about some other star. 121.247.218.225 (talk) 05:22, 23 January 2011 (UTC)
It is not probable in the next few years. Evidently a reporter misunderstood an astronomer - the report I saw on CNN said "it could be as early as 2012 or not for millions of years", which indicated a significant gap of understanding on the part of the reporter (It could be as early as now). There is no news here, just the stuff years to decades old about shrinkage and that it will eventually blow, which is already well documented in the article. Tarl.Neustaedter (talk) 05:42, 23 January 2011 (UTC)
Thanks Tarl.Neustaedter. While you were posting this reply, I was searching for other news articles for Betelguese. All that gibberish I came across explains this event happening in next 2-3 years created unwanted flurry. Stricter policing needs to be implemented to control media's dissemination of hype of this kind. —Preceding unsigned comment added by 121.247.218.225 (talk) 05:55, 23 January 2011 (UTC)
The talk that its going to go Supernova, could be a cover up, for all the planet X hype. I mean if planet X exists, and becomes visible to everyone, what better way to hide that it really does exist? Just say the star has gone Supernova!!!! Cmark304 (talk) 00:28, 16 February 2011 (UTC)
Confusing density comparison
I noticed this recent edit changed 10 to the power of minus five to ten to the power of minus three to make the sentence read:
If we compare such star matter to the density of ordinary air at sea level, the ratio is roughly 1.286 × 10−3
This would then claim that Betelgeuse's density is about one 800th that of sea level air.
However, note 7 contradicts this with:
Betelgeuse density ≈ 3.680 ×1031 kg ÷ (2.335 × 1027 km3 × 109) ≈ 1.576 ×10−5 kg/m3
...
Calculations for the Earth's atmosphere:
...
Atmospheric Density ≈ 5.148 × 1018 kg ÷ 4.200 × 1009 km3 × 109 ≈ 1.226 kg/m3.
The ratio is clearly 10−5 and not 10−3.
I therefore edited the text in an initial attempt to avoid future confusion, but more needs to be done. The reader was likely confused by the unclear language, ambiguous mathematical syntax and switching from kilometres (km) to metres (m) and mixing of kilogram (kg) and gram (g). I suggest the explanation should stick to kg and m exclusively, avoid abbreviations and use parentheses to avoid ambiguity. -84user (talk) 13:16, 3 February 2011 (UTC)
Which millennium?
Solving the riddle of mass-loss will be the key to knowing when a supernova might occur, an event expected anytime in the next million years, with some speculation it could even occur in the next millennium.
Nothing is "according to Wikipedia". Wikipedia is a tertiary source, _always_ check references.
That said, Antares is listed in SINBAD as being about 600 ly away, and A. Richichi reports an angular diameter 41.3 milliarcsecond, measured by lunar occultation. Betelgeuse is listed at about the same distance, and Harper et.al. report a slightly larger angular diameter of 42-44 milliarcseconds. That leads to a larger physical dimension for Betelgeuse.
In summary, what we know indicates they are of comparable size given the error margins we have. Betelgeuse is probably larger (and is seen as larger from our vantage point), but our uncertainty about distance is larger than the perceived diameter differences.
Astronomers Believe the Supernova will happen soon
I believe that they were Australian, and they were saying that the star will go boom in time for 2012, making it as if we had 2 suns in the sky. Is that worth making a section about, or at least additional info in regards to it's supernova candidacy? - Guest — Preceding unsigned comment added by 69.47.115.203 (talk) 15:57, 30 June 2011 (UTC)
the text must be in error, for the distance calculation using parallax. the distance in parsecs is 1 divided by the parallax angle in arcseconds,[1] which for 0.180 arcseconds would work out to 5.55 parsecs, not 56.. I went hunting through the reference given, but could not find the calculation in the external text, whereas I did find "We find that the photocenter changes with viewing angle at the fraction of a milliarcsecond level, while the change with VLA frequency in a given snapshot is smaller". So I am fixing the text to '0.0180' arcseconds. - 174.137.243.141 (talk) 20:44, 10 September 2011 (UTC)
I'm just getting back into the article after being gone for a few years. Thanks for catching the error and making the correction. Your perception was correct. Here's the source material: Michelson. --Sadalsuud (talk) 14:34, 14 June 2012 (UTC)
Review for FAC readiness
Saw Casliber's request over at WP:ASTRO and came to do a look-see.
"However, with distance estimates in the last century that have ranged anywhere from 180 to 1,300 light-years from Earth, calculating its diameter, luminosity and mass have proven difficult. " I'd take this out of the lead, as it's both too short to explain why this was the case, and too puzzling by itself.
Absolute magnitude doesn't need to be mentioned in the lead. There's an infobox.
awww, not sure I agree with that one as absolute magnitude is a pretty key attribute, but we'll see how consensus goes on that one. Casliber (talk·contribs) 06:36, 2 May 2012 (UTC)
"Betelgeuse appears to change shape periodically" ... "Betelgeuse has a complex, asymmetric envelope" - kinda the same thing. That paragraph could be tightened and merged with the preceding one.
Discuss I've reworked this section in the lead and brought some clarity to the distinction between 1) "changing shape" (a photospheric phenomenon ~5.5AU) and 2) "asymmmetric envelope" (circumstellar matter ~400-1400AU), so as to avoid any confusion. The first sentence now reads "In 1920, Betelgeuse was the first star (after the Sun) to have its photosphere measured." instead of "... its angular diameter measured. The latter sentence now reads "...Betelgeuse has a complex, asymmetric envelope caused by colossal mass loss obscuring its surface—an envelope that is roughly 250 times the size of the star itself..." with the word "surface" blue linked so the lay person understands that "surface" and "photosphere" mean the same thing in the context of stellar dynamics. Any thoughts?--Sadalsuud (talk) 21:36, 12 June 2012 (UTC)
Bear in mind the lead should convey the current state of understanding of the star. Leading up to each fact about it with an extended 'this was tricky to measure' is unhelpful to the layperson.
point noted In addition to conveying the "current understanding" of the star, I have also attempted to convey a "feel" for the ongoing debate that is occurring. Pardon my obvious bias, but this is one of the reasons I believe this Betelgeuse article (among the thousands already on the internet) is truly useful. When I first started researching the star, I was amazed that there was such a plethora of conflicting "facts" surrounding Betelgeuse. It was thoroughly confusing. One "authoritative" website said this and another contradicted it. It was at that point that I realized that to serve the Wikipedia community, we had to bring some context to the debate, so the reader could make sense of all the divergent opinions "out there". Consequently, I will attempt to remove language that creates this sense of "iffiness", as you point out, while simultaneously helping the reader to understand the "big picture". Hope this helps.--Sadalsuud (talk) 22:04, 12 June 2012 (UTC)
"Astronomers believe" - rather than appealing to authority, keep the same tone of 'this is the understanding' as the previous paragraphs.
"Currently in a late stage of stellar evolution" - I'd add something like 'proceed through its expected life cycle' before saying when it'll go supernova.
There's eight citations to ref 12, which is an entire book. I'd break these out into references to specific pages to ensure the citations can be verified (ie. looked up for further info by those who are keen). eg. citation style on Priscilla Fairfield Bok if an example is handy.
"he noted an increase in activity from 1836–1840, followed by a subsequent reduction. In 1849, he noted a shorter cycle of variability" - be careful to state in the first use of this that 'activity' means 'a cycle of changes in brightness'.
need to research This paragraph is an inherited section from perhaps 4-5 years ago. Before reworking it, I'll take some time to research it so I know the representations are accurate.--Sadalsuud (talk) 22:30, 12 June 2012 (UTC)
"researchers have since conducted multiple investigations ranging from the ultraviolet to the mid infrared with controvertible results." I think I know what's trying to be said, but it could be shorter: eg. "have since tried the measurement at other wavelengths."
"The 1950s and '60s saw important scientific developments" - needs to end with "have a significant impact on our understanding of the structure of red supergiants like Betelgeuse." to explain the otherwise digression.
I'm getting the impression at this point that the lead needs to mention 'Improving the measurements of Betelgeuse has long been a driver for improvements in astronomical imaging technology'. That would justify saying 'it is tricky'.
Discuss Pursuant to your other insights, the lead has been reworked numerous times. So I think the issue of "trickiness" has been addressed. Certainly the challenges associated with Betelgeuse have, along with other stars, driven astronomers to find better ways to image the heavens. I would be a little uncomfortable, however, making the claim "Betelgeuse specific", as the quest for better instrumentation has been central to scientific inquiry since the days of Galileo. When you have a chance, please read the latest version of the lead and let me know if it works or whether I've unwittingly created other problems. Thanks.--Sadalsuud (talk) 03:51, 13 June 2012 (UTC)
"This finding of a diminishing radius coupled with a relatively constant flux puts into question some of the fundamental theories of stellar structure." definitely going to need a reference for that. I don't think that justifies a WP:BLUE.
All deleted It took some time to complete this step. But with a review of the recent Ravi/Townes article, it looks like the contraction is due to activity in the star's circumstellar environment and not the star itself. Changes have been made throughout the article to reflect this new information.--Sadalsuud (talk) 15:23, 16 August 2012 (UTC)
"For decades astronomers have understood that red giants dominate mass return to the Galaxy creating opaque outer shells," ... "vast plumes of gas being ejected into the surrounding atmosphere with distances approximating 30 AU" - 30 AU != Galaxy-scale. I think that first bit could stand a reference from Binney and Tremaine or similar; you're talking about Galaxy-scale processes, not red giant processes.
"As the century unfolds" poetic = good, but time-specific = bad, unfortunately.
"In large cities in the Southern Hemisphere " - clarify that this means at the same time as the preceding sentence. Does need to be spelt out as S. Hemisphere will skip reading the part relating to the N. Hemisphere.
"As Rigel, with a nominal apparent magnitude of 0.12, has been reported to fluctuate slightly in brightness, by 0.03 to 0.3 magnitudes,[37] it is also possible for Betelgeuse to occasionally outshine Rigel and become the seventh brightest star." - put this sentence the other way around
"If our eyes were sensitive to radiation at all wavelengths, Betelgeuse would appear as the brightest star in the sky" - that's the kind of thing that should be mentioned in the lead.
Discuss I like the idea, tried inserting it in the lead, then I realized I would lose the reference if I did so? So what's more valuable, an unreferenced lead, or a referenced Visibility statement? Personally, I'd prefer to keep it in the Visibility section as it adds strength to that section.--Sadalsuud (talk) 22:31, 12 June 2012 (UTC)
Check for ALMA measurements.
done I didn't know what ALMA was so I googled it and ended up here: ESO's ALMA Observatory. Two observations: 1) ALMA won't be completed until 2013, and 2) Much of the cutting-edge work being done on Betelgeuse is being done at another ESO observatory, the VLTI in Chile, for which we have many references. So I think we're covered.--Sadalsuud (talk) 08:53, 15 June 2012 (UTC)
The last two sentences of the Gaia paragraph are irrelevant to an article on this star and can be cut.
Image of the VLA dish is cute but can be cut. Article is well imaged.
Discuss Oops! It's taken me 4 days to finally notice this item. Sorry. The image was deleted, but I reinserted it. My reasoning was that this is the very telescope that is responsible for the current parallax value and distance per Harper of 643 ly. If useful, I could change the caption to reflect that, but will be happy to defer to others on this issue.--Sadalsuud (talk) 23:01, 12 June 2012 (UTC)
Although showing Betelgeuse on an H-R diagram would be nice, since it's important in that sense as well.
Discuss Interesting you mention this. I fully agree. In fact, I had uploaded an image into Commons, but due to my inexperience, it was deleted six months later. I believe the image plays a valuable role in the article as it clearly depicts Deneb as being more luminous than Betelgeuse, when in fact Betelgeuse is the brighter star. I would really appreciate some help in uploading this pic as it is by far the most descriptive I've seen. Here's what we had: File:Hertzsprung-russel Detail.jpgHertzsprung–Russell diagram identifying supergiants like Betelgeuse that have moved off the main sequence.
I found the file on my old hard disk. Comparing it to other versions on the internet, it's probably the one with the highest resolution. But in terms of free usage, I'm not sure where to go. Here are the many other Sources for this image
Awesome! Why don't we try this: I'll upload the one I have, use the same licensing tags, and if you think the resolution is OK, we can go with it. If not, just delete it.--Sadalsuud (talk) 08:51, 16 June 2012 (UTC)
OK. Here it is. Looks pretty good... and oooooooooohhhhh, entering all those names would have been pretty intense!?!!!--Sadalsuud (talk) 10:43, 16 June 2012 (UTC)
"Recently another instrument, the Astronomical Multi-BEam Recombiner (AMBER)," - cull acronyms to mention 'a new instrument on the VLTI' is producing results rather than overloading the text with a full name that is never later referred to.
done Reduced fluff where possible but decided to keep the AMBER for 4 reasons: 1) it follows the theme of the previous paragraph (i.e. "multiple eyeballs" on a star) 2) VLTI is doing the most advanced research on Betelgeuse right now, and so the AMBER is going to factor more and more in astronomical news, 3) Wikipedia still does not have an article or sub-section on the AMBER that can be blue linked, and 4) AMBER referenced 8 times in the article, if we include footnotes.--Sadalsuud (talk) 00:10, 15 June 2012 (UTC)
The whole paragraph "To overcome these challenges" is a digression into techniques. While interesting, much of it isn't about Betelgeuse. Move to a different article.
Discuss Thanks for the insight. If it's OK with everyone, I think I'll take a different tack, reducing unneeded fluff while making it more Betelgeuse specific. As a non-scientist who has struggled to understand all the scientific literature on Betelgeuse, I have found that short contextual discussions like this are very useful in "putting all the pieces together", thus allowing the lay person to understand the specifics as they relate to Betelgeuse itself. I will update this post, when I've completed the edits on this paragraph for a final opinion. Thanks.--Sadalsuud (talk) 19:08, 13 June 2012 (UTC)
Discuss OK, I've cut out a lot of the fluff, synthesized three sentences into one, made it Betelgeuse specific, and repositioned it for the lay person by using the analogy of human depth perception. I think it's a useful contribution to the article, especially as a sequel to the previous paragraph. Any thoughts?--Sadalsuud (talk) 22:58, 14 June 2012 (UTC)
Probably can prune a little more - for instance does "The idea is fairly simple." add anything? If we remove it, do we lose meaning? Otherwise, I think the paragraph is pertinent enough to Betelgeuse to keep actually as it is integral to understanding. Casliber (talk·contribs) 02:21, 16 June 2012 (UTC)
" the group, under the leadership of John Weiner, published a paper showing" - > The group showed. Everyone does stuff by publishing papers. Similar phrasing like "produced a document " etc can also go.
This section becomes a back-and-forward where every paper in the recent literature is discussed in detail. This brings the section into the territory of comparing and contrasting primary sources, rather than letting the sources do that themselves. The section needs to be much more succinct to avoid this.
discuss I'm not sure how to address this issue. Please read the other discussion posts in orange. The central issue, it seems to me is "How do you characterize a debate?" when there are many researchers using different technologies to solve the same riddle. We could, of course, just give the reader a "bottom line" answer and leave out the debate altogether, but in my opinion, that would be a real disservice to Wikipedia readers, given all the conflicting information one comes across on the internet. Some guidance on this central issue would be much appreciated.--Sadalsuud (talk) 09:14, 15 June 2012 (UTC)
yes this is a tricky one. I just read it again and feel the detail helps educate the reader. Not sure what I'd lose - need to think about it some more. Casliber (talk·
Agreed That is how I see it too. Most articles you read on Betelgeuse only give you a tiny snapshot and often these tiny snapshots conflict with one another, making it very difficult for a reader to understand the whole picture. This is where the Wikipedia article on Betelgeuse excels. So I like the idea of trimming to make the article more succinct, but let's not sacrifice "the debate". That's what makes this article unique on the internet and a real contribution.--Sadalsuud (talk) 13:56, 17 June 2012 (UTC)
" this study encompassed a 15-year horizon at one specific wavelength". Unneeded use of italics; the section's phrasing can display the importance of the long-baseline study.
" the spectrum of this star has served as one of the stable anchor points by which other stars are classified" - another important point for the lead
"where there is no star formation region—an implausible scenario." - rephrase, eg. "which is implausible as there are no star formation regions."
done Changed to: "Given its current space motion, a projection back in time would take Betelgeuse around 290 parsecs farther from the galactic plane—an implausible hypothesis, as there is no star formationregion there."
"Although the radial velocity and proper motion for the 25 Ori subassociation have yet to be measured, α Ori's projected pathway across the heavens does not appear to intersect with it either. Also, formation close to the far younger Orion Nebula Cluster (ONC, also known as Ori OB1d) is doubtful. " Summarise. "Neither the close-by ONC or the 25 Ori subassociations are plausible candidates".
"young stars in Orion where masses greater than 10 solar can be found in abundance" -> abundant kindred high-mass young stars
Done I can see it's a little wordy but decided to condense it this way, so as to retain its specificity: "Like many young stars in Orion whose mass is greater than 10 solar, Betelgeuse will use its fuel quickly and not live very long."--Sadalsuud (talk) 15:12, 17 June 2012 (UTC)
rm " Sirius, by contrast, with a radius of 1.71R☉, would be roughly the size of a soccer ball" as too many comparisons: Sun is sufficient.
"where light could take over three years just to escape" - reword: Betelgeuse is not a black hole.
Fix the clarification needed tags.
The section Circumstellar dynamics could do with being more succinct. I got quite lost in places.
need to research Agreed. I will do what I can to tighten it up. This will take some time however as the star's extended atmosphere is one of the most focused areas of research today, given that it holds the key to understanding mass loss. I can see that Kervella and others have already published a dozen new papers on the subject.--Sadalsuud (talk) 13:47, 14 June 2012 (UTC)
I wonder whether para 3 in Circumstellar dynamics on rasalgethi etc. should be moved up above the preceding para. It does predate the conclusory para 2 (?) Casliber (talk·contribs) 22:19, 30 June 2012 (UTC)
Actually, I think we can lose (or move to stellar mass loss article) the sentence "All stars exhibit mass loss. Rates vary from about 10−14 to 10−4 yr −1 depending on spectral type, luminosity class, rotation rate, companion proximity, and evolutionary stage" and reword the next segment to: "German astronomer Martin Schwarzschild proposed monster convection cells as the likely cause in red supergiants. Prior attempts to explain mass loss in terms of solar wind theory had proven unsuccessful as they led to a contradiction with observations involving circumstellar shells." Then maybe reduce "Other theories that have been advanced include magnetic activity, global pulsations and shock structures as well as stellar rotation." to a footnote (??) -can then trim and append the next section of Karvella onto this one. Casliber (talk·contribs) 13:20, 1 July 2012 (UTC)
Makes a ton of sense. Give me a day to play with it. I just want to make sure we provide enough context that the reader understands the current inquiry regarding mass loss. I was actually reading a 2011 article yesterday that might provide a better lead in. Regarding the Rasalgethi paragraph, it's history and we could probably move the whole thing to the Stellar mass loss article. It could really use some help. I'll get back to you on this one in 24 hrs. Thanks. --Sadalsuud (talk) 21:16, 2 July 2012 (UTC)
Yes, a very common issue is discovering an article on a concept is missing large amounts of content when you're beefing up a related article on some entity. I'll watch what you do and wait until you say the word. Casliber (talk·contribs) 09:36, 3 July 2012 (UTC)
done OK. Worked on it and yanked the history paragraph. It's pretty succinct, now, and all the deleted info I still have in my sandbox for future work on Stellar mass loss. The paragraph that starts with Kervalla, I may rework, depending on what I find out. But that new info from Levesque on supernovas... blows your mind, doesn't it (sorry for pun... but I couldn't resist). I never realized it when we started working on this article, but Betelgeuse is an incredibly exciting star to study. Regarding the sub-section Asymmetric shells, let me give some thought to that. I know Iridia thought it was a little tedious. But given that Betelgeuse's nebula holds the key to understanding critical issues relating to stellar evolution, I'm a little reluctant to do too much trimming. Let's see what happens in the next week as I continue to read other papers.--Sadalsuud (talk) 10:44, 3 July 2012 (UTC)
"AMBER instrument on ESO's Very Large Telescope Interferometer" I'm sure this already had an acronym.
done It did, and so the text has been rigorously edited in both places.
Sometimes they're 'astronomers', sometimes people from X institute, sometimes (particularly the older publications) Famous Name. And sometimes people have titles, other times not, eg. "Professor J. Craig Wheeler"
discuss I'm not sure what the recommendation is here - perhaps too many references to too many people? I can try to reduce these references, but here's the challenge. Betelgeuse is one of the most studied stars in the galaxy and the inquiry is rapidly evolving with many different viewpoints. So our knowledge of Betelgeuse is anything but static. It's because of this that I've tried to "frame the debate". That way, when readers come across new or conflicting information somewhere, they have a REFERENCE which provides context. In conclusion, I'll give some thought to this, but let me know if "framing the debate" is perhaps NOT the right approach and the article would be better served by taking a different tack. Your insights are much appreciated. Thanks.--Sadalsuud (talk) 23:40, 14 June 2012 (UTC)
I think Iridia is suggesting there be more consistency in describing people. I have had the same issue in many articles I've developed. If you standardise it too much, the prose starts to sound wooden, and some people are hard to describe (e.g. trying to describe Christiaan Hendrik Persoon's nationality...). I think it is fine adding who people are from time to time as it gives context as to why we are reading about their contribution, so am happy to leave as is. Casliber (talk·contribs) 10:15, 16 June 2012 (UTC)
done Thanks for the insight. I'll continue to look for ways to streamline, but your advice on "sounding wooden" is quite helpful indeed. It's a tricky balance, succinctness vs meaning/character. I don't think anyone wants an article that is so monotone, it bores you to tears.--Sadalsuud (talk) 15:20, 17 June 2012 (UTC)
"seven times the Neptunian orbit" - too many comparisons
Trim the popular culture section: the movie sequel, Tolkien and Cthulhu, along with a few other references including the non-notable song, can go, unless they can be shrunk to a single sentence. Ships can stay.
The lit review is clearly comprehensive so not worried there. I would do yourself a sweep for close paraphrasing; I think by your references the accuracy of citing the sources is good. But be careful of how closely the sentences are paraphrasing the sources. Becoming more succinct can help there.
The lead, once redone, should probably have three paragraphs.
And go over the sourcing for each and every image to confirm they are all free-use. Possibly also prune a few down: it's quite image-heavy, though they are arranged and sized well.
I removed - "In MalayalamThiruvathira തിരുവാതിര and in Tamil the star is named Thiruvathirai திருவாதிரை." - as nothing much came up to reference it on google, and I can't see an associated story etc. Happy to revisit if something turns up. Casliber (talk·contribs) 19:09, 23 June 2012 (UTC)
Frustrated - I've searched and read alot about ancient Chinese astronomy (e.g. here but can't find anything which notes Betelgeuse's name as Shēnxiùsì. I will ask a person who can read chinese characters to see if it says this on File:Dunhuang Star Atlas - Orion.jpg. Sadalsuud, do you understand chinese characters...? The one on the map that should be Betelgeuse (in oranged-in black circle - top left) has no writing next to it.....(???) Casliber (talk·contribs) 20:56, 24 June 2012 (UTC)
The name 參宿四 can be found here (page from National Museum of Natural Science, Taiwan.) Since 參 is the traditional form of the simplified character 参, this is essentially the same name given in the article. According to [2], the first two characters, the name of the asterism containing Betelgeuse, are read as shēnxiù. The third character, meaning "4", is read as sì. Spacepotato (talk) 06:46, 25 June 2012 (UTC)
This paper notes on p. 172 that Herschel had noted Betelgeuse to be brighter than Rigel on October 24 1837 and November 26 1839 (and equal to Rigel on (November 13 1836), and Allen had stated it was the largest (brightest?) star in the northern hemisphere on December 5 1852.
Question is, is it worth adding these dates to the article (my thinking is leaning "yes" as it gives a reader an idea of frequency (are there others? has it been none since I wonder...), and if so then in the body of the text or as a footnote....
Casliber (talk·contribs) 03:23, 6 July 2012 (UTC)
Just noticed this. I agree. It's an interesting detail, so I just went ahead and added it to the Nascent discoveries section. Noticed that you already had the ref in the Mythology section, so added that too.--Sadalsuud (talk) 15:54, 16 August 2012 (UTC)
I edited the section about the structure of the atmopshere, which is strangely called "Asymmetric shells". I tried to make it clear that all those shells actually overlap, i.e. they are not concentric (and even not symmetric). I also made other changes trying to make sense of what had been written. I do not like the fourth paragraph ("The radio-telescope images ...") and suggest it to be rewritten. It looks like a foreign body in otherwise smooth text. Ruslik_Zero18:52, 16 August 2012 (UTC)
Yes, it can be tricky turning a segment from a narrative/story into an "encyclopedic" one. I do like a bit of narrative sometime but this article is so big....Casliber (talk·contribs) 20:33, 16 August 2012 (UTC)
I trimmed a bit at the start - the question is what to do about the quote by Jeremy Lim - strictly speaking it should be de-quoted and trimmed, but a conversational tone does lighten up and liven up the prose a little, which might be fairly dense - I suppose I am happy for the former, but can see a rationale for leaving as is too. Casliber (talk·contribs) 20:47, 16 August 2012 (UTC)
Ok, I need to read more papers before I can make changes, but one of the problems is that it is not clear to which part of the atmosphere "3,450 ± 850 K" refers to. Ruslik_Zero18:54, 17 August 2012 (UTC)
Thanks for your input here. I would direct you to Haubois 2009 where most of this information comes from. The name "Asymetric shells" was chosen largely because of the aforementioned article and this photo from ESO: Flames of Betelgeuse. The image suggests certain asymmetries in Betelgeuse's extended environment. Here's the definitive article on the subject: Kervella 2011. We can certainly change the heading of this sub-section, if you think it's inaccurate. As far as I can tell, it's a decent representation of the subject matter, particularly given the last sentence of the intro paragraph, which comes from Haubois.--Sadalsuud (talk) 17:08, 18 August 2012 (UTC)
Apparent magnitude
At Talk:Aldebaran#Apparent_magnitude_2 there was some confusion about the visible spectrumapparent magnitude vs the J band apparent magnitude. Sadalsuud changed Betelgeuse so that the vmag and jmag would be listed together in the infobox. Currently at Aldebaran the vmag is listed in the top section (Observation data) while the jmag i listed in the 2nd section (Characteristics). Is the formatting for Betelgeuse something that should also be done for the other bright near-infraredJ band stars to prevent confusion by the readers? Thank you for your thoughts. -- Kheider (talk) 16:16, 3 September 2012 (UTC)
Topic raised at FAC: the notes with calculations
At this article's FAC, I queried the extensive footnotes. I should have made clear that I'm not referring to footnote 1, but to notes 2 through 7. Here is the initial interchange with the nominator:
Now. Those notes. They are unsourced, arcane, looooong, look to this untrained eye to be original research and my initial view is that they should not be there. I am open to arguments as to why I am wrong :-) hamiltonstone (talk) 13:42, 5 September 2012 (UTC)
Ya, they're a little much, I have to agree. Let me start with the short answer, then we can look at each note separately. Point #1: I don't think the notes constitute original research since they are all routine calculations–high-school math, and a few formulas from Wikipedia. Point #2: Betelgeuse, when you start to research it, is a confusing star. There is a ton of information out there, much of it does not agree, a lot of it is dated, and research is proceeding so rapidly that even the experts don't agree. So the intent from the beginning was not to give the reader a "fait-accompli" and thus add to the confusion, but rather a rich mosaic of the important points, so they could make sense of it all. In a few instances, notes were needed. Point #3: I, as a non-scientist, wanted to understand–hence the use of analogies like Wembley Stadium, the mango and noctilucent clouds. If you tell me that a star has a density of 1.576 × 10−5 kg/m3, I have no idea what that means - hence the use of analogy. Unfortunately, scientists seldom if ever use such analogies, so there are no references. The best you can do is high-school math; that way the reader can follow your logic, if they want to. Now for each note:
Note 1. Apparent Size Table. In trying to understand all the conflicting information on the star's diameter, I created a spreadsheet. Once done, I thought "Hmmm! Maybe readers will find this useful." If you think it's overkill, we can just delete it.
Note 2. Betelgeuse Radius. This is a really valuable note. Right now, there are many articles on the web saying that Betelgeuse has a radius equal to the Jovian orbit of 5.5 AU. See APOD 2010. If Perrin's hypothesis is right however, we might see 4.3 AU real soon. So at least with this note, the reader can understand why such a vast difference.
Note 3. Speed of contraction. I just used some routine math to get a sense of how fast a photosphere could contract, given what was observed. We can omit this information altogether. It's not that critical.
Note 4. Luminosity. Every article you read on Betelgeuse "out there" quotes a different luminosity figure. To me, that's confusing. So that's why I provide the standard luminosity formula so readers can make sense of the vast divergences in the articles they read.
Note 5. The mango analogy. This is my favorite one. I just love visualizing myself inside of Wembley Stadium and imagining the Earth as a one-millimeter Pearl. It's experiential, and here's the math to back it up.
Note 6. Betelgeuse Volume reduction. Once again, I just wanted to understand what it meant if Betelgeuse's radius contracted, what that would mean in terms of volume. Wow! 680 million suns in 15 years. That's mind boggling!
Note 7. Noctilucent cloud analogy. Finally, just another attempt to take something esoteric like atmospheric density and relate it to something on Earth.--Sadalsuud (talk) 19:47, 7 September 2012 (UTC)
While I appreciate and support the editors' objective of relating the article content to easily understood concepts, we can only carry this so far, if the reliable sources fail to do so. I want to make some suggestions.
In some cases, I agree that the notes constitute lengthy, but nevertheless routine calculations. However, as routine calculations, they do not need to appear in the article. I suggest that those calculations used to generate particular results can be included up in some sort of collapsed box at the top of the article talk page, if anyone wants to check them, rather than cluttering up the article space. I think the calculations in notes 3, 5 and 6 meet this threshold. Despite looking more complex, the calculations in note 2 represent simply multiplications or divisions, and also are routine. However, they do rely on a formula, and that concerns me a bit. Which brings me to my second point:
In other cases, I think the "routine calculation" argument is too much of a stretch. I do not think the bar for 'routine' is "high-school math, and a few formulas from Wikipedia" (quoting Sadalsuud above). I think it is lower than that. The policy page says "Basic arithmetic, such as adding numbers, converting units, or calculating a person's age, is allowed provided there is consensus among editors that the calculation is an obvious, correct, and meaningful reflection of the sources". I am not convinced the use of formulas, particular that in note 4 (which BTW needs a reliable source itself), can qualify. In the case of note 4, the calculations are used to support the following claim: "Nevertheless, since Betelgeuse is a pulsating variable star, there are times where the star's luminosity could theoretically exceed 200,000L☉". That is the kind of fact for which I think a straight-out reference should be relied upon, rather than a complex calculation by our own editors. If no source includes that figure in its range of luminosity estimates, there may be a reason, and the sources are better placed to consider that than we are, so that sentence may have to be dropped.
Note 7 presents a slightly different issue. The initial sets of calculations are routine, but they are then plugged into a "model" of the earth's atmosphere to come up with the altitude estimate. I think that is going too far (and would need references in any case). In any case, I think it is unnecessary. I suggest the note and the analogy, while colourful and interesting, be abandoned in favour of the plain English comparison made by the author of one of the two sources already cited: "Such star material has a density of less than one ten-thousandth the density of ordinary air" (AAVSO article).hamiltonstone (talk) 00:45, 9 September 2012 (UTC)
I removed note 7 (Noctilucent cloud analogy) - I think readers can better visualise a "red-hot vacuum" much better than earth's mesosphere, which renders the latter comparison unnecessary. Casliber (talk·contribs) 05:58, 9 September 2012 (UTC)
<scratches head> actually, my immediate reaction to "red hot vacuum" was 'huh? but it's a vacuum...' I liked the "one ten-thousandth the density of ordinary air" - that was the comparison that made sense to me. But whatever... :-) hamiltonstone (talk) 06:23, 9 September 2012 (UTC)
Interesting - I guess "vacuum" to me is a more vivid and immediate image...and I assume that all vacuums are relative and not absolute in their vacuum-ness.... Casliber (talk·contribs) 08:42, 9 September 2012 (UTC)
Both analogies, I believe, are important. The "red-hot vacuum" analogy comes from Burnham's Celestial Handbook, which I understand is a "classic" in astronomy. The problem with the analogy however, is most people understand the word "vacumm" to mean "absolutely nothing". So the analogy is confusing for most. It was initially for me. Also, the Wembley Stadium picture has this in the caption: "...while the air in the stadium is actually far more dense than the star itself." So a reference to air is important. It's the thing we can relate to the most on this planet.--Sadalsuud (talk) 10:41, 9 September 2012 (UTC)
Elegant solution?
In thinking about this issue in the last 2 days, a thought occurred to me that might be the most elegant solution. Why not siphon off this information to other articles and blue link from this article? Let me give you one example–Note #4 on Luminosity. That formula actually comes from the Luminosity article. I've put a lot of work into that article recently, and what I realize now is that Note 4 is not just about Betelgeuse, it's also about the challenges that astronomers face with every star. So this discussion would be very appropriate in the luminosity article itself, and if it is set up with its own heading could be easily blue linked from the Betelgeuse article. What do you think?--Sadalsuud (talk) 07:50, 9 September 2012 (UTC)
OK. Note 4 (now note 3 following recent deletion) is easy to move, as already mentioned. In fact, by moving it to the Luminosity article, a theoretical discussion of "potential luminosities" would be appropriate as it would highlight the challenges that astronomers face and thereby enhance the reader's understanding of the concept of luminosity.
Note 2 could probably be made to fit in the Angular diameter article, although that article will need some work, so the Betelgeuse calculations don't look completely out of place. Like Note 4, the formulas used for Note 2 come from the Angular diameter article. So all we are doing is taking information already in the article and giving them a practical application.
Regarding Notes 5&6 (now 4&5 following deletion), I like the idea of a "collapsed box", but don't know how to do that in Wikipedia. Casliber, do you? If so, maybe you can focus on Notes 5&6 and I'll focus on Notes 2&4. Sound like a plan?--Sadalsuud (talk) 11:11, 9 September 2012 (UTC)
Both the radius and luminosity notes have now been deleted in the Betelgeuse article and recreated in the Luminosity article. A simple ref has been created in the Betelgeuse article that reads: "For detailed computations of stellar radius and implications relating to the star's luminosity, see the Computational challenges section in the Luminosity article". Any concerns here?--Sadalsuud (talk) 11:47, 15 September 2012 (UTC)
I don't know how this is going to go with other editors, but it would certainly help if the relevant sections of the Luminosity article had citations, which are currently absent, including citations for the luminosity formulas in general (before one even gets to the "computational challenges" section). But I doubt this is going to be an important issue at the Betelgeuse FAC. Regards, hamiltonstone (talk) 11:51, 15 September 2012 (UTC)
Thanks. I'll see what I can find. The article, of course, still needs a lot of work, but it's coming along. I tried inviting other editors into an improvement discussion on the Talk page, but so far no feedback.--Sadalsuud (talk) 12:23, 15 September 2012 (UTC)
As you'll see, I added short instructions to each note that read as follows: "For computations relating to Betelgeuse volume, click [show]". I think it helps. I could not find a way to edit the text in the box itself. Replacing "Extended Content" with "Betelgeuse volume calculations" would be best. Thoughts?--Sadalsuud (talk) 12:15, 15 September 2012 (UTC)
I'm not convinced that the text regarding the star's diameter is adequate, and as I've noted above and at FAC, the use of calculations and formulas makes me all the more nervous. I figure there's a reason that key journal articles choose not to convert angular diameters into object size. One of those reasons, of course, is the disagreement about how far away the star is. In any case, I wonder if the text can be improved.
The article has this: "They also included a theoretical allowance for limb darkening yielding a diameter of 55.2 ± 0.5 mas—a figure which equates to a radius of roughly 5.5 AU (1,180 R☉), assuming a distance of 197.0 ± 45 pc.[note 2]" One can't have a single result ("roughly 5.5AU") when assuming a massive distance range (152 to 242pc). I know the next sentence addresses this, but it reads oddly. I admit I haven't yet come up with a concrete proposal to improve the text, though.
This sentence "Nevertheless, given the angular error factor of ± 0.5 mas combined with a parallax error of ± 45 pc found in Harper's numbers, the photosphere's radius could actually be as small as 4.2 AU or as large as 6.9 AU" has a footnote, but that note is just a cross-reference to the calculation notes. I get the point being made, and I've no reason to doubt the calculations, but I'd be a lot happier if this sort of discussion was published in the literature somewhere - maybe a popular science astronomy article?
The article has this: "This conclusion, if further corroborated, would suggest an average angular diameter for Betelgeuse closer to Perrin's estimate at 43.33 arcseconds, hence a stellar radius of about 4.3 AU (924R☉)[note 2] in lieu of the widely accepted Jovian orbit of 5.5 AU.[37][71]" I had a look at reference 37. I could find nothing that came close to the article text of "the widely accepted Jovian orbit of 5.5 AU", and no reference to Perrin's estimate. The NASA astronomy picture of the day reference uses the Jovian orbit reference, but that hardly constitutes "widely accepted". However, it does raise the question: how did NASA decide that radius? What was their source, and can we use it too, instead of relying on our own calculations?
I'm rewriting this section, noting the above concerns. I hope to have something done in the next few days. As you have already surmised, the problem comes down to a lack of consensus on two issues: 1) distance and 2) angular diameter. I've googled magazine articles, but they were either vague or understandably non-committal: Astronomy Now, and Bad Astronomy, though Astronomy Magazine, APOD2010 as well as AAVSO were fairly explicit on the issue of the Jovian orbit (5.5AU)--Sadalsuud (talk) 21:21, 12 September 2012 (UTC)
That's great that you found those sources talking about the diameter in terms of AUs / Jovian orbit. I'm a bit busy right now, but will keep an eye out and will be back soon. hamiltonstone (talk) 23:45, 12 September 2012 (UTC)
Ok. I think most if not all the concerns have been addressed. Let me know. It will require a little tweeking here and there. There are some minor things I'd like to add, but for the most part it's done.
I also had to modify the Parallax section, incorporating the van Leeuwen data, that way teeing-up the discussion that follows in this section. I also debated what name would best describe the section while avoiding the ambiguity you highlighted. There were several I considered: 1) Stellar diameter, 2) Stellar disk, 3) Stellar size and 4) Angular size. In the end I decided on simply "Diameter". I prefer it over "Size" as the latter strikes me as too generic. "Diameter", implies both definitions of stellar size−angular diameter and radius (i.e. R☉).--Sadalsuud (talk) 17:40, 14 September 2012 (UTC)
Also take a look at the last paragraph of the Approaching supernova section. There was a recent contribution from Credulity as to all the speculation regarding the "Supernova around the corner" prediction, which I've reworked a little, adding the Ravi article as a reference. Any concerns here?--Sadalsuud (talk) 06:29, 15 September 2012 (UTC)
I just got slapped for using an unpublished reference, albeit one that was already included as a reference in this article. But how about Wolfram Alpha? NASA and ESO press releases? Own calculations? APOD?!? You can't seriously think those are reliable sources of information? Lithopsian (talk) 19:31, 1 November 2012 (UTC)
Not specific to this article, but prompted by a recent edit and reversion. The solar symbol can be represented by a unicode character or by a MathTEX circle with a dot in it. I find the math styling to be cumbersome and ugly. The font and spacing doesn't properly match the surrounding text which is jarring, it takes forever to appear on large articles so I quite often run across unrendered pieces of markup, and in some cases it doesn't render at all depending on browser settings. The unicode character. in this case, renders immediately and consistently with the rest of the text. Discuss :) Lithopsian (talk) 12:00, 6 November 2012 (UTC)
Yes, I prefer it like so: M☉. I'm interested because I made some edits recently to place the unicode sun symbol into some articles to replace repeated cumbersome text descriptions, and want to see if that is generally acceptable before I do any more. Lithopsian (talk) 14:14, 6 November 2012 (UTC)
My problem with using M☉ is that it's unreadable, at least under Safari. The circle does not show up with a dot in the middle, it's a round thing. When zooming in to see individual pixels, it shows up with what looks like a triangle inside. Tarl.Neustaedter (talk) 19:57, 6 November 2012 (UTC)
Webkit support for high Unicode characters was always patchy but I thought they'd sorted it for the most part. Except on Android which still has a number of pretty bad problems. Lithopsian (talk) 11:25, 7 November 2012 (UTC)
The article gives the misleading impression that one or more binary companions are likely. It references a paper that suggest some knots in the circumstellar material were other stars, but ignores the multiple searches that have failed to find any support for this. It also quotes a more recent paper as not ruling out the companion, giving the impression that it is still likely, when in fact that paper says it is "very unlikely" that the features observed represent another star. Lithopsian (talk) 14:45, 17 November 2012 (UTC)
I was wondering how it read to an outsider. When we wrote it, we wanted to give the impression (because it reflects the literature) that you expect above - i.e. one study found some interesting evidence, but no-one else has seen this and it appears highly doubtful, all things considered. However, you're the first one to suggest the emphasis reads differently, so I wonder whether we have to rejig it to make it plainer (that it is unlikely). Have you got an idea on a rephrase? Casliber (talk·contribs) 19:21, 17 November 2012 (UTC)
Section 4, Star System, the main one that discusses this, is perhaps OK in itself. There is a statement in the Properties section that Betelgeuse has no known companion so that is hardly raising expectations. But then there is that last sentence of the introductory section: "Possible stellar companions orbiting within this circumstellar nebula may also contribute to the star's enigmatic behavior." Given its prominence in the introduction and the fact that no researcher is seriously considering this as an option, this seems to me to generate a misleading impression of the likelihood that Betelgeuse is a multiple system. Lithopsian (talk) 20:11, 17 November 2012 (UTC)
After working closely with Casliber for 2.5 years on Betelgeuse we were finally able to cross the FA goal line recently. There is, however, one concern that I have and which could really use your expertise. It concerns the nature of stellar mass loss.
Where we ended up in a pickle, was we needed to reference the luminosity figure for Betelgeuse. Fortunately, we found a recent article from Mohamed 2012 which provides a little infobox on page 2 showing a mean luminosity of ~120,000L☉. But in the infobox is a mass loss rate of ~0.03M☉ every 10,000 years which sources a 2001 article from Graham Harper. In 2009, however, ESO published a Betelgeuse article referencing Ohnaka2009 which quotes ~1M☉ per 10,000 years. It seems that the discrepancy has to do with episodic mass loss (huge gas plume) vs that which is emitted by the star's stellar wind.
So my question is simply this: Is the first paragraph of Circumstellar dynamics a fair representation of the facts?
No rush. There's a major conference on mass loss coming up in November. We're thinking of having the article featured on the main page then. I just want to make sure that the way we've summarized the information makes sense to an astrophysicist. Thanks again for any insights.--Sadalsuud (talk) 19:33, 19 October 2012 (UTC)
Well it took a month, but here are my thoughts:
It's not bad, though a bit heavy going to read. You seem to have described the relevant observations quite well, though it would be nice to have a concluding paragraph to the section which sums up what all these mean, in layman's terms.
1e-4 M_sol/yr is NOT the same as 1 M_sol every 10,000 years. The former is an instantaneous rate, whilst the latter is the average over a long time period. If the mass loss is episodic, the latter can be much higher than the former implies, because the star will go through periods of low- and high-mass loss rate. Don't re-write the measurements in this way. Compare 'the car was travelling at 10mph' and 'the car travelled 88,000 miles in a year' - they mean different things, despite being numerically equivalent.
Harper et al quote a mass loss rate of 3e-6 based on a combination of their model and earlier observations (section 8.1). I cannot see any estimate of Betelgeuse's mass loss rate in the Ohnaka paper, just a general statement about red supergiants (given as 'up to 1e-4'). Harper also references a value of 4e-6 found by Glassgold & Huggins (1986), and two other measurements of 1e-6. In the absence of any other information, I'd go with the Harper number and cite both Harper and Glassgold & Huggins. Delete the 1e-4 figure as misleading and not referring to this star.
I don't like the second paragraph of that section, which reads like a rehashed ESO press release. Really, what does it matter which instrument was used, or who did the study? That's technical information which is of interest to researchers in the field, but not general encyclopaedia readers.
There's no reason to talk up the mass loss from this particular star as somehow being massively important to the entire history of the universe. That's overblown, and belongs in the Stellar mass loss article, not Betelgeuse.
I used a source that gives the named brightness limit directly and I used "may" because the GAIA team has apparently weighed options to read out the CCD differently to get to bright stars and obtain better estimates than Hipparcos, presumably. Hekerui (talk) 13:55, 1 March 2013 (UTC)
Well, strictly speaking all stars we see are in the milky way....but if you're asking is it in the galactic plane, I am not sure - don't think so but need to check a star map. Casliber (talk·contribs) 19:57, 13 March 2013 (UTC)
The galactic equator passes through Orion, so Betelgeuse is close to the galactic plane. It's coordinates in the galactic sphere show it 9 degrees south of the galactic plane. Tarl.Neustaedter (talk) 21:54, 13 March 2013 (UTC)
Cool factoid. I'm writing a sci-fi novel about a high schooler who builds a spaceship and flies to Betelgeuse -- a coming-of-age story -- and this stuff is helpful. To get to Betelgeuse, he travels faster than the speed of light (which isn't possible in reality, right?) but are there any ideas of how such warp speeds could be possible?--Tomwsulcer (talk) 22:13, 13 March 2013 (UTC)
Yes thanks. I figured you knew more than most about this subject. And this stuff may possibly be related to Betelgeuse if (1) I finish my sci-fi novel in which a hero travels to Betelgeuse at warp speed (2) it gets published (3) readers want to know if such blistering speeds are possible to Betelgeuse. That is, my question above is probably almost certainly and most unequivocally irrelevant. :)--Tomwsulcer (talk) 23:22, 13 March 2013 (UTC)
Is it not terribly misleading to quote its distance to so many decimal places in the lead, (641.8 light-years) when its estimated distance, according to the side bar is only known by ± 146 ly ? Dave3457 (talk) 20:46, 21 November 2013 (UTC)
Had exactly the same thought. The statement is made twice in the article. Even if the star is travelling through a medium not originating from its own emissions and generating a bow shock, the density of that surrounding gas is so low that a person on a bicycle could probably be considered to be traveling at supersonic speeds in such an environment! One would have thought such meaningless concepts alluding to the speed of sound in space (where no one can hear you scream:-) would have been weeded out before this article was passed for FA status (particularly since it appears on WP's main page - making it a bit of an embarrassment). I suggest we replace the words 'supersonic speed' with 'high velocity'. Anyone any thoughts that can justify retention of 'supersonic'?1812ahill (talk) 20:40, 26 November 2012 (UTC)
I had remarked that in the featured article review: you can find the response there and note here whether you find it sufficient. Hekerui (talk) 20:57, 26 November 2012 (UTC)
This entire sentence: "Having been ejected from its birthplace in the Orion OB1 Association—which includes the stars in Orion's Belt—this crimson runaway has been observed moving through the interstellar medium at a supersonic speed of 30 km/sec, creating a bow shock over 4 light-years wide" is non-ecyclopedic langauge. " It's more suitable to a comic book. Starting a sentence with 'Having been ejected' is poor diction besides. I think it needs to be rewritten, and perhaps the following sentence as well, but I have not done it because this controvery exists. 72.179.53.2 (talk) 17:47, 28 November 2012 (UTC) Eric
The speed of sound in space is not meaningless. The sound speed is the speed at which changes in pressure can propagate in a medium, and while interstellar space is not dense enough that a human scream could be heard, neither is it a perfect vacuum in which a pressure wave could not propagate. Given the current state of articles addressing these concepts, perhaps it would be more useful if the supersonic re-directed to speed of sound? In the long term, coverage in supersonic should probably be made a bit more general to explain this. James McBride (talk) 23:21, 26 November 2012 (UTC)
Featured article review discussion: http://wiki.riteme.site/wiki/Wikipedia:Featured_article_candidates/Betelgeuse/archive1 The term supersonic is used correctly here and there is not a suitable alternate term. I would suggest linking the word "supersonic", but unfortunately the relevant Wikipedia article is basically just a few pretty pictures of jet planes with very little physics. "Transonic" has a paragraph about some supersonic flows in astrophysics, but hardly worth linking to. Lithopsian (talk) 21:25, 26 November 2012 (UTC)
Well ok, I guess, since it's already been discussed. It still seems odd to me. We don't talk about boats travelling through water at supersonic speeds, even though that's what they do by this standard. And I think the average reader is going to think "700 mph" (or metric equivalent) when told something is supersonic. Kendall-K1 (talk) 21:41, 26 November 2012 (UTC)
After dredging through the FA review I found:
I have reintroduced the word "supersonic" as it is used throughout the primary literature. See: Mohamed 2012, Introduction to Stellar Winds and Bow shock. I'm no astrophysicist, so I will defer to others on this issue. But it appears that this is an important distinction when describing stellar winds.--Sadalsuud (talk) 14:54, 15 October 2012 (UTC)
I appreciate the points being made, but although the term 'supersonic' is used in academic circles when discussing interstellar bow shock, I question whether it is appropriate for an encyclopedic article, particularly when the linked term refers users to pages about Earth's atmosphere as that could lead to confusion for non-experts. Also I note retention of 'supersonic' was done on the basis of only a singly user's decision (correct me if I am wrong). I also suspect that the word 'supersonic' is used in interstellar bow shock literature to ditinguish it from the more familiar phenomenon associated with boats as pointed out by the previous poster.1812ahill (talk) 21:52, 26 November 2012 (UTC)
Betelgeuse is moving at over 30km per *second*. What part of supersonic are you having problems with? You think there is no "sonic" in a vacuum? You thought interstellar space was a vacuum? I'm not a big fan of removing correct and useful statements just because someone doesn't understand them and can't be bothered chasing the references. If a large proportion of readers are not likely to understand the statement, don't just remove it. Explain it better. Lithopsian (talk) 22:12, 26 November 2012 (UTC)
Incidentally there is also a Wikipedia article on Bow Shock specific to stars, but that may just confuse things further. The fact that a star is moving supersonically and the fact that it has a bow shock are two separate things, although both can occur together. However a bow shock may simply be caused by a supersonic stellar wind. Lithopsian (talk) 22:12, 26 November 2012 (UTC)
Well thank you for that rather rude response. What part of 'there is no sonic in a medium as tenuous as that in interstellar space' do you not understand. The lede statement 'moving through the interstellar medium at a supersonic speed of 30 km/sec' is in itself relatively meaningless because the phrase 'the interstellar medium' implies a kind of ether disproved by the Michelson-Morley experiment. Don't know how good your Physics is (you dont have a user page), but such statements referring to 'x km/s' are usefully backed up with 'relative to [something or other better than the interstellar medium]'. The word 'sonic' when used even in our own atmosphere is pretty meaningless. Ask any supersonically flying pilot - it depends on pressure and temperature. I'm bowing out of this conversation now as it seems to have taken a turn for the worse. As I stated before the word is no doubt being used to distinguish it from ship's bow shock.1812ahill (talk) 23:08, 26 November 2012 (UTC)
The interstellar medium has nothing to do with the Michelson-Morley experiment. It instead refers to the gas and dust that exist in the space in between stars. It has a well defined pressure and density in the same way that the Earth's atmosphere does, and that speed and pressure likewise describe a speed of sound. As you point out, the pressure and density are location dependent, but that does not make the concepts of sonic or supersonic speed meaningless. It merely means that treating the speed of sound as fixed is an approximation, rather than being exactly true. James McBride (talk) 23:30, 26 November 2012 (UTC)
Sorry can't help myself. True, as you say, the local 'interstellar medium' rotates around the galactic core along with the rest of the galaxy. I just question the point of using a word involving sonic when the particles creating the phonons in that medium probably have a mean free path on the order of AUs.1812ahill (talk) 23:47, 26 November 2012 (UTC)
Whether or not you question the value of it, the sound speed in the interstellar medium is an incredibly useful and important concept. For one particularly important example, see the article on the Jeans instability, which has an intuitive explanation that relies upon the sound speed in a cloud in the interstellar medium. In short, if the timescale on which gravitational contraction occurs is faster than the timescale on which sound waves cross the cloud, then the cloud will collapse. This entire discussion suggests that there needs to be some work done on making the articles addressing sound speed and supersonic more general. I strongly disagree that the solution is removing the term supersonic from the article on Betelgeuse. James McBride (talk) 00:02, 27 November 2012 (UTC)
Having looked at your user page, I must concede. My (uncompleted) PhD was in nuclear physics. You clearly know more about this subject than I do. Caveat: the link to supersonic speed is inappropriate. Or, as you suggest that article needs extra work. Best wishes.1812ahill (talk) 00:29, 27 November 2012 (UTC)
I could, of course, be making that all up. :) I agree that the link given now is not ideal; I actually suggested above that for the time being, directing users who click on supersonic to the article on the speed of sound might be more useful. James McBride (talk) 00:39, 27 November 2012 (UTC)
And I assume as one of WPs directives, good faith (or whatever it's called), and you seem to know what you're talking about:) Just as a matter of interest, since you're online, what kind of velocities are we talking about in one's average interstellar medium - if the concept is actually meaningful in our Earth's atmosphere centric view. (Sorry if I'm forgrtting this not a forum)1812ahill (talk) 00:49, 27 November 2012 (UTC)
There is not any one number for the interstellar medium (ISM), as it includes gas in a few different phases. Each phase is in rough pressure equilibrium. This includes important, probably dominant, contributions from non-thermal sources of pressure, which actually means that a quantity like the Alfven wave speed (which describes the speed at which magnetic pressure propagates, rather than thermal pressure) is often more important than the speed of sound. Anyway, each phase is in rough pressure equilibrium, but they have very different temperatures and density, so a blob of gas could move through the cold component of the ISM at supersonic speeds, but be subsonic in a warmer ISM component (in much the same way, I suppose, as a jet could be supersonic at one altitude and subsonic at another). At order of magnitude level, in the cold ISM, the sound speed is of order 1 km/s, while for the warm ISM it is closer to 10 km/s. James McBride (talk) 01:16, 27 November 2012 (UTC)
Huthoff & Kaper (2002) give the speed of sound in neutral interstellar gas as 1 km/s at 100K, 10 km/s at 10,000K, and 100 km/s at 1,000,000K. A million kelvin is an extreme condition that only occurs in a few places such as in bubbles blown by supernovae or OB supergiants. Thus most runaways are moving fast enough to be supersonic. In addition, young hot stars have solar winds that are comfortably supersonic wrt the interstellar medium. Even the sun is thought to produce a bow shock where its wind drops to subsonic speeds, but this is very difficult to observe for a normal star and from the inside. Lithopsian (talk) 17:21, 27 November 2012 (UTC)
Thanks for the enlightenment. I'll have to read up on this more - a sound speed of the order of km/s implies very fast moving particles to me in such a tenuous environment. The idiosyncracies of 'sound' in the ISM as you describe do further re-enforce the almost otherworldy sense of 'sound' in the ISM as compared to the understanding the lay reader (probably) has of our familiar Earthly pressure wave, where magnetic or thermal pressure effects (except maybe in storms or fires) are of minimal importance, because our atmosphere is more like a fluid (in the sense that most people understand that word). Thanks for taking the time to explain. Well past my bed time now, so I'll call it a night. Again apologies for turning this into a forum.1812ahill (talk) 02:19, 27 November 2012 (UTC)
I wasn't even thinking of "sound" in a "vacuum" when I questioned "supersonic" for 30 km/sec (Mach 100). The reason why _I_ laughed out loud when I saw it was that it reminded me of the Far Side cartoon, "Young Carl Sagan on his first date": "Just look at all those stars, Gloria, there must be _hundreds_ of them!" Kotabatubara (talk) 02:11, 28 November 2012 (UTC)
"The last part of the name, "-elgeuse", comes from the Arabic الجوزاء al-Jauzā', a historical Arabic name of the constellation Orion, a feminine name in old Arabian legend, and of uncertain meaning. Because جوز j-w-z, the root of jauzā', means "middle", al-Jauzā' roughly means "the Central One"."
That is basically true.. the Arabic word al-Jauza means any black sheep that had a white line "in the middle" of it. This gave the name elgeuse to Orion because of the white line of the belt!
--Mando Salama (talk) 17:20, 1 August 2014 (UTC)
Not that the belt stars were seen as the white line on the black sheep, but there are reliable sources of course for the meaning of the word al-Jauza.. any classic Arabic dictionary, e.g LISAN AL-ARAB, or MUKHTAR AL-SEHAH, etc.
Burnham gives an alternative translation as “The Front Leg of the White-belted Sheep”, saying it’s favoured by “[s]tudents of Arabic” (p.1289), but doesn’t explicitly state that it refers to the Belt asterism. His choice of word (? or his authority’s) might be telling, but I think it would still be synthesis to say so without a firmer source. (The allusion might be to the Equator, for example.) Regardless, I think we“d be justified replacing the “uncertain meaning“ in the article with the marked-sheep definition, however worded; as long as we refrain from commenting on the reason for the association, readers are free to speculate as they will.—Odysseus147900:59, 6 August 2014 (UTC)
The Islamic celestial globe image in the Etymology section does not depict Betelgeuse at all in this perspective. It is approximately centered on the spring equinox point. The human figure just right of center is not Orion, but Andromeda. Orion is located about at the horizon at the 7 o'clock position. I've looked for a similar image with an angle showing Orion, but to no avail so far. If I can't find one, I'll remove the image.
There is a statement in the article that Betelgeuse has lost 1-2 M☉, with two cited references. I couldn't find this within the references, and personally believe it is just plain wrong. Total mass lost to date for a star at this stage of evolution should be considerably higher. Are these values in the references and I missed them? I will be editing this and related statements shortly and am likely to replace this with a more reasonable relation between the initial and current masses. Lithopsian (talk) 14:19, 15 February 2015 (UTC)
Has that been there the whole time (i.e. did we put it in before FAC?)? Don't remember now. Am a bit snowed under but will try and look. Happy if you take the lead on this. Cas Liber (talk·contribs) 19:56, 15 February 2015 (UTC)
It was added 16th Aug 2010 "Ethereal cubed" import by Sadalsuud. The only ref then was the Kaler page which states "(Betelgeuse so far having lost over a solar mass)". I don't like using that page as a ref anyway (not primary, and increasingly out of date), but it looks to me like that statement was mis-interpreted. Lithopsian (talk) 21:21, 15 February 2015 (UTC)
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