Talk:Alpha Centauri/Archive 3

From a hypothetical A or B planet
This section of the article has very few citations to sources. The section also contains the following statement:

"For example, some theoretical planet orbiting about 1.25 AU from Alpha Centauri A (so that the star appears roughly as bright as the Sun viewed from the Earth) would see Alpha Centauri B orbit the entire sky once roughly every one year and three months (or 1.3(4) a), the planet's own orbital period."

Is this original research? I wonder if a planet could orbit stably at such a distance from Alpha Centauri A given the proximity of Alpha Centauri B, and, in particular, I wonder if that could persist at that distance for a year, as the sentence seems to imply. The rest of the paragraph elaborates on other things, but no source is cited. This seems like a problem to me. Thanks, Attic Salt (talk) 01:55, 24 June 2018 (UTC)

I see, now, that the matter of stability of planetary orbits has been previously discussed:. Though, I still think that this section is largely original research. Attic Salt (talk) 03:07, 24 June 2018 (UTC)
 * A 1.25 au orbit around A would likely not be stable; B's eccentric orbit would destabilize it, which was the point of the original paper. It's not impossible to find a stable orbit at that distance, but it's not trivial (you have to fiddle with inclination and eccentricity to get a non-chaotic orbit) so is unlikely. It does appear that section is WP:OR, someone trying to convey the relative brightness of the secondary star compared to the primary. Tarl N. ( discuss ) 03:12, 24 June 2018 (UTC)

Also, what does it mean one would "see Alpha Centauri B orbit the entire sky"? Attic Salt (talk) 03:39, 24 June 2018 (UTC)
 * What they meant to say is that it would behave like an external planet (e.g., Jupiter), as the inner planet's year goes by, they'd see the secondary go from behind (their) sun, to full opposition as a midnight sun, to back to behind their sun again. I'm not sure it's worth trying to make that better, since it's all OR anyway. Tarl N. ( discuss ) 03:52, 24 June 2018 (UTC)
 * See this discussion. I think this comes from here. Arianewiki1 (talk) 06:24, 24 June 2018 (UTC)
 * It appears that large parts of the Alpha Centauri article are inspired by this source. Is it considered reliable? I note that parts of it read like personal opinion, saying, for example "As regarding the stability of the orbits, it seems to me that he just brushes off the significant problems of perturbations." in regard to published work on planetary orbit stability. Attic Salt (talk) 15:37, 24 June 2018 (UTC)

"Routine calculations" are given as an example of what is NOT "original research" for Wikipedia. If so, then what might be acceptable sources for brightness of full sunlight in lux? — Preceding unsigned comment added by 2001:7D0:82AE:C780:8588:77AD:EC9F:526F (talk) 18:47, 24 June 2018 (UTC)

This section contains these two sentences:


 * "An observer on the hypothetical planet would notice a change in orientation to very-long-baseline interferometry reference points commensurate with the binary orbit periodicity plus or minus any local effects such as precession or nutation."


 * "Assuming this hypothetical planet had a low orbital inclination with respect to the mutual orbit of Alpha Centauri A and B, then the secondary star would start beside the primary at "stellar" conjunction."

I propose removing the first, as it seems oddly technical. I don't understand the second. What does it mean "the secondary star would start"? Thoughts? Attic Salt (talk) 14:44, 22 July 2018 (UTC)
 * I assume they are referencing the fact that if the orbits are at low relative inclination, you'll get an "eclipse" of one star going in front of the other. Tarl N. ( discuss ) 16:54, 22 July 2018 (UTC)
 * Okay, but the word "start" is confusing. How to fix? Also, are you okay with simply removing the other sentence? Attic Salt (talk) 17:34, 22 July 2018 (UTC)
 * I'm good with you removing the other sentence. Heck, I think the entire section should be removed as mostly WP:OR. As for start, that's probably poor phraseology from someone trying to describe a yearly cycle. Tarl N. ( discuss ) 00:52, 23 July 2018 (UTC)
 * After just trying to remove confusing stuff, I went ahead and removed the entire section.
 * Yes - it was very overinvolved - and lacking in a reference from a peer-reviewed journal. One line that might be worth keeping is about proxima being as bright as a 4th-5th magnitude star from the system. Cas Liber (talk · contribs) 19:58, 25 July 2018 (UTC)

Kinematics
This section contains this paragraph:


 * "Edmond Halley in 1718 found that some stars had significantly moved from their ancient astrometric positions.[73] For example, the bright star Arcturus (α Boo) in the constellation of Boötes showed an almost 0.5° difference in 1800 years,[74] as did the brightest star, Sirius, in Canis Major (α CMa).[75] Halley's positional comparison was Ptolemy's catalogue of stars contained in the Almagest[76] whose original data included portions from an earlier catalogue by Hipparchos during the 1st century BCE.[77][78][79] Halley's proper motions were mostly for northern stars, so the southern star Alpha Centauri was not determined until the early 19th century.[69]"

I note that this is mostly not about Alpha Centuari. I suggest substantial reduction, but I wonder what other editors think. Attic Salt (talk) 12:19, 26 July 2018 (UTC)
 * Yeah - context is necessary but this is too much context. Cas Liber (talk · contribs) 13:49, 26 July 2018 (UTC)
 * Yup. I might say something like "Halley's earlier work on determining stellar proper motions was mostly on northern stars, so Alpha's proper motion was not determined until the early 19th century." Tarl N. ( discuss ) 19:47, 26 July 2018 (UTC)
 * Done. Attic Salt (talk) 12:57, 27 July 2018 (UTC)

Rotational velocity
The article contains a few mentions of "rational velocity", even giving its formula, but then focusing on rotational period. I don't see any reason to discuss rotational velocity, and so I propose that these mentions be removed. Any objections? Attic Salt (talk) 15:13, 12 August 2018 (UTC)
 * Makes sense. I believe the reason rotational velocity even comes up is because that's the value we can measure with a spectrograph (spectral line broadening), and from that we can derive the rotational period. For the purpose of this article, we don't need to get into such details. Tarl N. ( discuss ) 15:20, 12 August 2018 (UTC)
 * Exactly, it is a measured value. The rotational period is derived from it, and even then is just an estimate because we don't know the exact rotational inclination or radius although we have a pretty good idea of the radius.  It is worth noting both that there are other measurements giving different values, and that the margin of error on that value is considerable, making the claim of a short period than the sun somewhat dubious.  The projected rotational velocity should probably be in the starbox, even if nowhere else.  Lithopsian (talk) 18:39, 12 August 2018 (UTC)
 * I tried to insert a new parameter, rotational velocity, into the star box, but I couldn't get it to work. Apologies. Attic Salt (talk) 13:46, 13 August 2018 (UTC)
 * I think you have to add it to Template:Starbox_detail. Modify with caution, this affects every star article in Wikipedia. Tarl N. ( discuss ) 14:25, 13 August 2018 (UTC)
 * That is outside of my comfort area. Attic Salt (talk) 14:34, 13 August 2018 (UTC)
 * Done. Not hard.  starbox detail already supports this.  I just slammed in the values and refs I could get my hands on quickest, so they might be able to be improved.  At least they are referenced now.  Citation bot made a lot of changes, so I'm going to double-check those, and there are quite a few other things that look like they need tidying up.  Lithopsian (talk) 14:54, 13 August 2018 (UTC)

Nationalities of various astronomers (though not all of them)
Some of the mentions of various astronomers include their nationalities (or, even, where they were born). In other cases, no mention is made of nationalities. I propose that we remove most of these, unless it is related to a specific culture that is being discussed (for example, "English explorer Robert Hues brought Alpha Centauri to the attention of European observers"). Any objection? Attic Salt (talk) 15:21, 12 August 2018 (UTC)
 * I went ahead an removed some of the nationalities that didn't seem relevant to "Alpha Centauri". Attic Salt (talk) 21:26, 12 August 2018 (UTC)
 * Someone at FAC might ask for them all back...just sayin' Cas Liber (talk · contribs) 00:29, 13 August 2018 (UTC)
 * Probably a consideration for much of the article. Deleting badly-worded or sourced stuff is all well and good, but this article is important enough that it should be aiming for FAC sooner rather than later.  That requires completeness, so always bear in mind what can be improved or even expanded, rather than just stamping out the rubbish.  Of course, ruthlessly stamping out the rubbish and then expanding with better-quality text is another way to go.  Lithopsian (talk) 20:55, 13 August 2018 (UTC)

Proposal: Remove section: View from this system
I propose removing the section entitled "View from this system". I don't think it adds much understanding. That is my opinion, so I thought I'd check with interested editors first. Thanks. Attic Salt (talk) 20:02, 13 August 2018 (UTC)
 * Here I disagree. The section is indeed convoluted, and may not have much scientific use, but with the amount of science fiction existing and being written for the system, it's worth documenting what we can about how the sky will appear. It's useful for those who are either fact-checking or just curious. Documenting the positions of a few bright stars is achievable without WP:OR, and documenting magnitudes of the components as viewed from close orbit about each of the others is another such case. In both cases, being careful to document the exact mathematical transforms so future editors can fact-check them.
 * Give me a couple of days to propose a re-written section, rather than deleting it entirely. I'd call it something like "skies from &alpha; Cen" and try to give the flavor of what would change without going into the appearance of asterisms. Tarl N. ( discuss ) 20:39, 13 August 2018 (UTC)
 * Okay, thank you. Please go ahead and rewrite. Attic Salt (talk) 20:56, 13 August 2018 (UTC)
 * I went ahead and worked this section over. Attic Salt (talk) 14:30, 24 August 2018 (UTC)

Erroneous footnote
Several months ago I tried to edit the first paragraph under the header "Predicted future changes", but the author of that paragraph reverted it. I think the whole paragraph is just obvious stuff that doesn't need to be mentioned. But in any case, there's a footnote at the end that says "Changes in position angle (θ) are calculated as; θ − θo = μα × sin α × (t − to ), where; α = right ascension (in degrees), μα is the common proper motion (cpm.) expressed in degrees, and θ and θo are the current position angle and calculated position angle at the different epochs." I think this is wrong, and if we really do have a group of astronomers and physicists who have offered to help update this article (as said above — perhaps can bring this to their attention), then I would like someone of them to check this point. Here I copy my argument which I gave above:

I think the formula should say:


 * $$\theta-\theta_0=\mu_\alpha(t-t_0)\sin\delta$$

In other words with sin δ instead of sin α (with δ being declination). The author of the footnote gave this Google Book link and this link to a book by Heintz called Double Stars. First of all, I have no problem with his Equation 5. That is concerning the precession of the earth's axis, and so it's right that it depends on the right ascension of the double star in question, because the motion of the double star in equatorial coordinates as the axis of the earth moves depends on where the double star is compared to the equinox (the intersection of the ecliptic with the equator). But the equation which we're discussing (in your footnote) has nothing to do with the position of the ecliptic, so it shoud not depend at all on right ascension. Now, to see how proper motion in the east-west direction affects the position angle, it suffices to take the case of two stars that are initially at RA zero and at declination δ and δ+ε, both at the same distance r from here. Converting to rectangular coordinates, we have
 * $$x=r\cos\delta$$
 * $$y=0$$
 * $$z=r\sin\delta$$

for the first star and
 * $$x=r\cos(\delta+\epsilon)$$
 * $$y=0$$
 * $$z=r\sin(\delta+\epsilon)$$

for the second. Now let them both move $$r\tan(\mu_\alpha(t-t_0))\cos\delta$$ in the y direction. Now the RA of the first star is
 * $$RA=\arctan\frac{r\tan(\mu_\alpha(t-t_0))\cos\delta}{r\cos\delta}=\mu_\alpha(t-t_0)$$

but for the other star it's
 * $$RA=\arctan\frac{r\tan(\mu_\alpha(t-t_0))\cos\delta}{r\cos(\delta+\epsilon)}\sim\mu_\alpha(t-t_0)\frac{\cos\delta}{\cos(\delta+\epsilon)}\sim\mu_\alpha(t-t_0)(1+\epsilon\tan\delta).$$

This is an asymptotic expansion for small ε. Now, in the sky the second star will be approximately ε further north than the first, and $$(\cos\delta)\mu_\alpha(t-t_0)\epsilon\tan\delta$$ further east, so the new position angle is approximately
 * $$\theta\approx\arctan\frac{(\cos\delta)\mu_\alpha(t-t_0)\epsilon\tan\delta}{\epsilon}\approx\mu_\alpha(t-t_0)\sin\delta.$$

Since at the start the position angle was zero, we have:
 * $$\theta-\theta_0\approx\mu_\alpha(t-t_0)\sin\delta$$

as I said. Actually this equation is only valid when the two stars are the same distance from us, but if we talk about the position angle of the line of nodes, then we can write
 * $$\Omega-\Omega_0\approx\mu_\alpha(t-t_0)\sin\delta$$

and this is valid no matter what the inclination is. But of course this is only asymptotically true (for small $$t-t_0$$).

Eric Kvaalen (talk) 12:47, 28 August 2018 (UTC)


 * Eric, you have obviously given this lots of thought. My first reaction, however, is that this is original research (thoughtful research). If you are willing to accept this, then perhaps we should, as you apparently suggest some time ago, remove the whole section on future motions. I see that some of the section is cited to sources. But insofar as scientists sometime engage in this "future prediction stuff", things that will never be verified in the lifetime of the scientist making the predictions, I just think it is kind of a waste of time. So, yes, I support either removing the section or reducing it a lot. Attic Salt (talk) 13:09, 28 August 2018 (UTC)
 * , so I think you are only suggesting that the footnote be removed? I can agree with that, since it doesn't add much to the article even if it is correct. Attic Salt (talk) 12:49, 29 August 2018 (UTC)


 * Yes, I would be happy with just removing the whole paragraph. I do think, though, that if we don't remove it the footnote at least should be removed, even though the equation is found in a book. We should not give false statements in Wikipedia, and if it can be proved false by mathematical "research", it's still permitted to remove it. The idea of "original research" should only be applied to what we put ín Wikipedia, not what we don't put in.
 * So go ahead and remove the paragraph. Or I will if there are no more comments.
 * Eric Kvaalen (talk) 13:08, 29 August 2018 (UTC)
 * , What concerns me is that some material might be inserted into Wikipedia by editors making seemingly simple calculations with equations that they have misinterpreted. As I understand it, Wiki permits simple calculations, but this assumes the equations are properly understood. Regarding removing the identified stuff, this is for you. Attic Salt (talk) 13:13, 29 August 2018 (UTC)

Nature and Components
The section Nature and Components contains the following sentence:

"Because the distance between the Sun and Alpha Centauri AB does not differ significantly from either star, gravitationally this binary system is considered as if it were one object."

What does the Sun have to do with this? I checked the cited source (to Wayback), and the Sun is not mentioned there. Attic Salt (talk) 16:28, 13 August 2018 (UTC)
 * Given the context of that paragraph, it should be distance from Proxima, not Sun, and I'd add a weasel phrase "for practical purposes" or something like that. I suspect that sentence got migrated from a discussion about why there is a distance (from Sun) listed for Proxima, but not for each A & B component.
 * Looking at that paragraph in more detail, I'd probably simply delete the sentence, I think it's mostly covered in the first sentence of the paragraph. <b style="color:green">Tarl N.</b> ( discuss ) 16:37, 13 August 2018 (UTC)


 * It is talking about the centre of mass. Calculations of motion is based on motion relative to the Sun. Arianewiki1 (talk) 10:43, 20 September 2018 (UTC)

Is this a "good" article now?
,, , , and other interested editors, is this article a "good" one? Attic Salt (talk) 20:45, 18 September 2018 (UTC)
 * Definitively not, since it has unsourced statements. The one that is tagged should be simple enough to fix.  With that out of the way, maybe.  Its certainly big.  I'm not a good article reviewer, but I could see a case for meeting the six good article criteria.  Personally though, I'd have reservations.  I think the split of Proxima Centauri could still do with some tidying, seems like about a quarter of this article should really be elsewhere.  I'm always wary of see also sections in supposedly comprehensive articles; they tend to mean the article isn't comprehensive (or they are just wikilink spam).  I'd also take a good long look at the notes section: very easy to slide in original research, or to hide away things that should either be explained properly or in the body.  The article structure doesn't fill me with glee either, gives the distinct impression that it randomly accreted cruft rather than being thought out, which I suppose is actually what happened.  So maybe ... Lithopsian (talk) 21:03, 18 September 2018 (UTC)
 * I agree with pretty much everything Lithopsian said. Years ago I tried to align this article like other star articles, but was reverted. Another editor (Arianewiki) left me this note. It was difficult to negotiate changes - you can see by his note on my page how he felt about the article. Anyway, I'll have a look too. Cas Liber (talk · contribs) 21:08, 18 September 2018 (UTC)
 * Seems like some WP:OWN at work there. User Arianewiki1 has been blocked indefinitely from Wikipedia for edit warring. Multiple requests for an unblock have been denied. Praemonitus (talk) 21:24, 18 September 2018 (UTC)

Surprise! Someone already nominated it, and it was recently:. Attic Salt (talk) 21:56, 18 September 2018 (UTC)
 * I'd seen the nomination, an obvious place to check for clues about what a real reviewer thought. Not very helpful though, because it was withdrawn before any meaningful progress.  Probably worth another go, but wait a few days and see if anyone can think of good things to improve first.  Lithopsian (talk) 10:43, 19 September 2018 (UTC)
 * Since the recent edits made by Attic Salt, this article has greatly diminished in quality. It needs significant work. There has been many recent changes that are either wrong nor understand the correct astronomical terminology. To suggest that it somehow qualifies for Good article criteria as it appears now is clearly inappropriate. Improving readability is good, but the facts presented have to be right.
 * Much of the early stable article was reached by agreed compromise. If you need to fix this article you'll need some adequate experts on the subject, as previously suggested.
 * As or the last two responses above by Praemonitus & Attic Salt it clearly says PA : ""Do not make personal attacks anywhere on Wikipedia. Comment on content, not on the contributor. Derogatory comments about other editors may be removed by any editor."" & ""It is as unacceptable to attack a user with a history of foolish or boorish behavior, or one who has been blocked, banned, or otherwise sanctioned, as it is to attack any other user."
 * As for this statement "Arianewiki1 has been blocked indefinitely from Wikipedia for edit warring." That is factually wrong, and I ask you to kindly strike/remove that please. Arianewiki1 (talk) 10:25, 20 September 2018 (UTC)
 * Nope. You are incorrect in your assertion about my behavior: my statement was purely factual and I didn't share my actual opinion of you or your behavior. Instead I was speaking to the message on Casliber's talk page: "Note: I have contributed much to this page – 713 edits according to the statistics." Please see WP:CIVIL. Thank you. Praemonitus (talk) 15:41, 20 September 2018 (UTC)
 * Also, Arianewiki1, when you say: "As or the last two responses above by Praemonitus & Attic Salt it clearly says PA ..." you seem to be asserting that I made a personal attack against you. I don't know what I wrote that offended you. Attic Salt (talk) 15:56, 20 September 2018 (UTC)
 * Praemonitus statement : "User Arianewiki1 has been blocked indefinitely from Wikipedia for edit warring." I was blocked for Violating BLP actually. Considering the difficult debate on my talkpage, defensively stating "my statement was purely factual" might be true, but the need to say it in they circumstances can be construed as WP:PA. Making wrong or even slightly hinted inference statements about blocked users is particular abhorrent because they can't actually defend themselves. Broadcasting other's 'difficult' circumstances, factual or not, just suggests perhaps a different motive.
 * The adage here appears like : When someone is down, you shouldn't kick. Yet, the adopted attitude seems instead, let's just kick even harder.
 * As for "Seems like some WP:OWN at work there." No evidence for this at all, and considering the efforts to get a stable article at the time, and the amount of vandalism, you might like to consider portraying the context in why it was written. What has this to do with "Is this a "good" article now?" So why the need to say these things? What's the point? Arianewiki1 (talk) 01:51, 21 September 2018 (UTC)
 * Why say how many edits you have had? It's irrelevant and speaks of an ownership attitude. Instead, I'm suggesting that seeking consensus is usually a better approach. Praemonitus (talk) 03:36, 23 September 2018 (UTC)

Inline references in the lead
One idea that strikes me for improving this article to good is simply to make the lead as clean as possible. This is by far the most important part of the article and if nothing else it creates a good impression. One thing I feel, although not everyone agrees, is that there should be no need for inline references in the lead of a good article. The lead should summarise the important points of the article and everything in the lead (of an article at good level or better) should be explained in more detail in the article, with references. References in the lead are unhelpful to most readers and simply add clutter where simplicity is needed. Lithopsian (talk) 10:48, 19 September 2018 (UTC)
 * Most of it was added to settle arguments of the facts, actually. It solved any ambiguity. Complex articles need complex cites and support. What you write above is opinion that is not supported by editing policy. 10:35, 20 September 2018 (UTC)
 * Incorrect. MOS:LEADCITE applies here. The lead should generally have fewer citations, with exceptions being settled by consensus. But if challenges are presented, that's usually cause for a cite in the lead. Praemonitus (talk) 03:33, 23 September 2018 (UTC)

What might or might not be critical information
With this edit:, added words that he asserted provide "critical information". I don't see how any of this is critical. Isn't "positive radial velocity" the same as "moving away"? Does the bit about "visual perspective" actually add any information to what is already noted to be "naked-eye visibility"? Personally, I think we need to minimise redundancy and fluff, but I thought I'd ask other editors about this. Thank you. Attic Salt (talk) 15:37, 4 October 2018 (UTC)
 * Not only not critical, but very sloppy wording. That stuff about "visual perspective" is weird and the "vanishing point" bit just wrong.  It also seems to be ungrammatical in its latest form.  Lithopsian (talk) 18:22, 4 October 2018 (UTC)

Confusion
I am confused on what Alpha Centauri defines; does it mean the physical triple system, or does it only refer to the binary system? What adds to the confusion is that there is a "binary system" section and a "nature and components" section. Also the starbox mostly just has information on Alpha Centauri A and B, and there is even a separate article on Proxima Centauri. — Preceding unsigned comment added by Sbznpoe (talk • contribs) 00:48, 29 November 2018 (UTC)
 * Alpha Centauri refers to the entire system. Per IAU action recently, two stars in the system have official names: A is Rigil Kentaurus and C is Proxima Centauri. B does not have an official name, other than Alpha Centauri B. Yes, it's confusing, many authors use different standards about what the names apply to, but the preceding is now what the IAU recommends. <b style="color:green">Tarl N.</b> ( discuss ) 01:14, 29 November 2018 (UTC)

Alright, thanks. Sbznpoe (talk) 07:22, 1 December 2018 (UTC)

Proxima Centauri cleanup
The status of Proxima Centauri adds much confusion in my reading of the article, and I feel like I already know a great deal about it. I can't imagine what it must be like for someone new the the subject. Probably this has been discussed ad nauseam in the past, inevitably since there was a split of Proxima Centauri but the article is still muddle. A simple example, "α Cen C" is in the starbox catalogue but not the rest of the starbox. The lead itself starts by claiming α Cen as the closest star system to Earth, then quoting a distance that is larger than the distance to Proxima Centauri. So we need some clarity about how to describe this star system when a physically associated component is not generally treated under the name α Centauri and has a separate article. Do we want to claim α Centauri as the closest star, fudge it by saying it is the closest star system, or explain that it forms part of the gravitationally bound group with the real closest star which is called Proxima Centauri (and α Centauri C in the context of the multiple star system)? Lithopsian (talk) 11:02, 19 September 2018 (UTC)
 * Some of the referenced stuff in the lede is mentioned in the body of the article, but some is not, like this phrase: "Alpha Centauri B is smaller and cooler, at 0.907 times the Sun's mass and 0.445 times its luminosity.[16]", and this cited source [16] is only used once (in the lede). My issue with some of this is that many numerical facts also appear in the info box to the right of the lede. So I wonder, should we be putting into sentence form numerical info already given in the infobox? Personally, I find it tedious to read some of the sentences in this article, with this or that star having this or that mass, luminosity, etc. I don't gain insight from this. Can we remove sentences that just repeat numerical info already in the infobox, and just keep numerical values in sentences when it is necessary to give insight? Thoughts on this? Attic Salt (talk) 13:01, 19 September 2018 (UTC)
 * Some people like words, some like numbers. Certainly there is key information that has to be in text, and probably the lead, for example the distance.  There is also some that may be subject to in-depth explanation, for example there is a whole table of parallax measurements that could do with some words; and a section on historical observations which has a lot of overlap.  There is also a section on the orbit.  Obviously, repeating some of the drier starbox facts like position is unnecessary, but explanation of things like the combined and individual magnitudes would be helpful to many people.  Lithopsian (talk) 13:31, 19 September 2018 (UTC)
 * Ideally, anything in the infobox should be discussed in the prose, since the infobox is only intended to be a summary of what the article states (especially in an article of this size). In the real world, it often isn't practical to wordify some of the very specialised, but still completely encyclopedic, facts and figures we use in astronomy (and spaceflight, for that matter; can you imagine trying to discuss a satellite's orbital elements in the prose? For a short article, a table with that data truly would be redundant). Use your best judgement. If something can be reasonably discussed in the prose or used in a table, then it should be. However, the lead is definitely not the place for those detailed figures, since the lead should be a summary of what is stated in the prose. Alpha Centauri B is slightly smaller and much cooler than the Sun would suffice. — Huntster (t @ c) 13:35, 19 September 2018 (UTC)
 * Okay, I will accept consensus, and I respect the more expert opinions of Lithopsian and Huntster. It remains my opinion, however, that standalone sentences like this star has this luminosity and this mass, etc. are uninteresting for most readers unless these numbers are coupled to some conceptual insight. I do agree that the numerical distance of Alpha Centauri is important and should be in the lede. Thank you. Attic Salt (talk) 13:42, 19 September 2018 (UTC)
 * Q. Is Proxima actually in orbit around the main pair or is it a co-moving star? This explains the alleged 'confusion' in the text. (The article has too many absolutes making statements false.) Arianewiki1 (talk) 10:41, 20 September 2018 (UTC)
 * Looks to be a pretty solid assumption now, as documented and referenced in Proxima Centauri. Not sure it changes much though.  Whatever the relationship, they are close enough to eachother to be considered a multiple star (ie. sometimes called α Centauri C) and we have to explain that while allowing that Proxima Centauri is treated as a separate star with a separate article.  Lithopsian (talk) 16:18, 20 September 2018 (UTC)
 * Quick ref: https://www.aanda.org/articles/aa/abs/2017/02/aa29930-16/aa29930-16.html — Huntster (t @ c) 16:58, 20 September 2018 (UTC)
 * The problem is few established binaries have periods exceeding 20,000 years, which is made worst by needing enough evidence to show the stars are actually attached. This same kind of problem is with Formalhaut, which is 0.29 pc apart. Although the article says it is a binary, evidence is not direct. Here "Fomalhaut forms a binary star ..." and "...for the two stars forming a physical binary." (A definition of binary stars is you need orbital elements. As the Huntsters linked article says: "...demonstrate that TW PsA is unequivocally a physical stellar companion to Fomalhaut,...", but also says "...common proper motion system TW PsA." Not a true definition of a binary star, though.
 * As far as I know, Proxima is in the same boat. Proxima might be considered a multiple system, but its not directly established as in orbit around AB. (it an assumption.) Even linked article says "...are gravitationally bound with a high degree of confidence." It does not say it is a binary, but still could be a common proper motion pair. One of the theoretical problems is that is how Proxima can stay linked to the main pair or billions of years but not be disrupted by multiple stellar encounters.
 * IMO, it is better to say ambiguous term not absolutes. In some other recent large number edits made Attic Salt they have just gloss over the uncertainty in our knowledge.
 * Also the article was originally split by User:RJHall, mostly to avoid confusion and stop continuous disruptive editing. Arianewiki1 (talk) 00:38, 21 September 2018 (UTC)
 * Are you here to help or just complain? None of your arguments contribute to cleaning up the article.  We have a reference showing an association between the stars today, and a long history of arguments both ways if you want to make a paragraph about it.  Either way, the distinction between a close α Centauri binary, Proxima Centauri, and the use of the α Centauri designation to include all three stars as a group (whether optical, binary, common proper motion, or who the hell cares) needs to be made clear to a reader who may not already know.  I feel that there is too much Proxima stuff left behind from the split and not enough clarity about what this article is about.  I've made a presumption that Proxima Centauri stays a separate article, it is already Featured and merging it here would make for one huge ream of text; hence that this article is, largely, about only the close binary pair (a wonderful hope except for the dangling end of α Centauri C!).  Lithopsian (talk) 21:03, 21 September 2018 (UTC)
 * Umm. Nothing changes. First sentence "Are you here to help or just complain?" You already know the answer, considering my previous contributions to this article, so I'll just ignore it. Nothing personal, but that is your own problem. Deal with it.
 * As for saying "...whether optical, binary, common proper motion, or who the hell cares." is actually the central point. (Note: A co-moving pair can be never an optical double. All it means is that it has a common origin. Assumptions either way, find that this. or any other article, is about verifiable facts not in making blind or incorrect assumptions.) Alpha Centauri, on many levels, is more about it being the closest star, and central is explaining that important fact. Proxima is part of that fact, and its relation to the main pair is paramount. This is why Proxima separate article alludes to the nature of that star in isolation. I once disagreed with RJHall on the original split, which is why you see the development that has been presented. It was frankly a compromise. I'm more than happy to take your suggestion in improve this article, but going over the trials and tribulations in agonising over old ground based on opinion ain't going to achieve anything. Been there, done that. (However, in compromise, that does not mean it is forever set in stone e.g. When the stable version was produced little was known about exoplanets, which is why the recently removed section detailed about the nature of a hypothetical planet around either star in the binary.)
 * You've said yourself "...or explain that it forms part of the gravitationally bound group with the real closest star which is called Proxima Centauri." My last response above shows that that is unproven and this/your view just might be an incorrect assumption. "Fudging it", frankly, just diminishes expressing our current knowledge, and just supplants ambiguity. I agree writing this in a comprehensible manner is hard because of its overall complexity, but availing such attitudes as given above, you'll never achieve any adequate or compromised solution. I might be wrong too, but articles here is about being on agreed consensus not airy-fairy personal inadequacies. Arianewiki1 (talk) 09:30, 22 September 2018 (UTC)
 * A split? Nope. The Proxima Centauri article was created in 2002; it wasn't split. RJHall's first edit was in 2005 and it was brought to WP:FA status in 2008. This article isn't even at WP:GA status yet; it has a "B" rating. Cas Liber has a lot of experience in bringing articles up to top notch status, so I believe his efforts would have been beneficial. Praemonitus (talk) 03:27, 23 September 2018 (UTC)
 * (belatedly) I think the best way of proceeding is fixing this article first with the most up to date/consensus literature and wording and then see how it contrasts with the Proxima article. Looking now, there is some repetition etc. Cas Liber (talk · contribs) 08:40, 7 December 2018 (UTC)

Binary system
Why is there even a "Binary system" section? Shouldn't that belong in sections like "Nature and components" or "Observation"? Sbznpoe (talk) 23:35, 6 December 2018 (UTC)
 * You are correct. I think the Binary system should be somehow moved into the "Nature and components" section. Cas Liber (talk · contribs) 00:06, 7 December 2018 (UTC)

Thank you for your edits. This article is a lot better now without the confusion. Sbznpoe (talk) 06:05, 7 December 2018 (UTC)

Thank you for your edits. This article is a lot better now without the confusion. Sbznpoe (talk) 06:05, 7 December 2018 (UTC)

Somehow it glitched so my thanks are copied. Sbznpoe (talk) 06:06, 7 December 2018 (UTC)
 * That's alright, I don't mind being thanked twice :) Cas Liber (talk · contribs) 08:37, 7 December 2018 (UTC)


 * All sorts of hangovers from the split of Proxima Centauri and a number of edit wars. Looks better now, but no doubt there could still be structural improvements.  I just had a quick look through and it seems fairly complete, but I'll have to scan recent literature and see if there is new research I haven't seen.  Lithopsian (talk) 14:05, 7 December 2018 (UTC)
 * There are still bits of information that are duplicated or missed. So just reading through....Cas Liber (talk · contribs) 18:40, 7 December 2018 (UTC)

What we call.....
So before 2016 and the advent of this, we'd all be calling them Alpha Centauri A and B, and Proxima Centauri...but now we have this and have the issue of the very familiar vs the official (also still seems odd to me to split the two common names and use one for A and one for B.) Just wondering who has strong feelings on what we use and why. Cas Liber (talk · contribs) 12:04, 9 December 2018 (UTC)


 * It does seem odd especially as the Alpha Centauri system contains multiple stars that cannot be separated without optical aid and the one they are calling Toliman is the dimmer of the two so could not have been known of in the ancient era which is where star names come from. Mtpaley (talk) 15:56, 9 December 2018 (UTC)


 * If this link is to believed someone is trying to make life very complicated by giving different ancient names to the visually indistinguishable main pair of stars in the system "These traditional names are now formally assigned to different component stars within the Alpha Centauri system: the International Astronomical Union has designated Rigil Kentaurus as Alpha Centauri A, and Toliman as Alpha Centauri B." Mtpaley (talk) 16:08, 9 December 2018 (UTC)


 * I agree that the IAU's adopted conventions make for some very strange situations, including this one. One thing to bear in mind is that while they are "official", the majority of the names are from from being in common use.  For example, this article is still called Alpha Centauri, not Rigil Kentaurus & Toliman, and I don't think there is any clamour for it to be renamed.  As for where the names came from, they are two relatively old and unrelated names for the single point of light as it was known, randomly assigned by the IAU to the two components that we now know of.  Some of the etymology is described in the article; Toliman is another 17th century Latinisation of an Arabic word for a group of stars in that area of the sky.  I feel we need to be very careful about creating a situation here rather than just reported one - this article is not too bad, but there are examples which I would call highly-promotional of proper names that simply aren't used by anyone in the real world.  Lithopsian (talk) 17:12, 9 December 2018 (UTC)
 * I was wrong. The article contained far too many uses of proper names referring to individual components.  I found this very difficult to follow, and in some cases the grammar was clumsy.  Better now, but we'll see if everyone agrees.  I know some people are very attached to proper names.  The juxtaposition of Proxima Centauri and Bayer-designated components can still be jarring, and I still feel there is too much detail about Proxima left in this article, but one day at a time.  Lithopsian (talk) 21:59, 9 December 2018 (UTC)


 * Personally I like the current version by Lithopsian. It gives mention to the official names that nobody is going to use but does the rest of the article with the normal names. Mtpaley (talk) 23:16, 9 December 2018 (UTC)
 * I also like the “normal name” version. Attic Salt (talk) 23:22, 9 December 2018 (UTC)


 * Is the term "Toliman" still being used anywhere? I think the OP was asking why this article uses different terms to refer to Proxima Centauri. Kortoso (talk) 03:23, 17 January 2020 (UTC)
 * By "anywhere", do you mean anywhere in the article or anywhere in real life? Toliman occurs all over the article.  Lithopsian (talk) 15:38, 17 January 2020 (UTC)

Latinisation?
The article says: α Centauri (Latinised to Alpha Centauri). A small point, and maybe I don’t understand, but where is the latinisation? Isn’t this still just Greek? Attic Salt (talk) 21:15, 9 December 2018 (UTC)
 * Latinisation "is the practice of rendering a non-Latin name (or word) in a Latin style". There is also the subtly different Romanisation which is simply transliterating non-Latin words into the Roman (Latin) alphabet.  Is Latinisation not the correct term for the spelling out of a Greek letter in Roman script?  Lithopsian (talk) 21:39, 9 December 2018 (UTC)
 * I see, because the Greek word is spelled out. Thanks. Attic Salt (talk) 21:42, 9 December 2018 (UTC)
 * Well, possibly, but don't take my explanation as gospel. I don't think writing α as alpha is strictly Latinisation, or Romanisation, but I don't know of a better term for it.  Lithopsian (talk) 12:15, 10 December 2018 (UTC)

Age estimates in "Physical properties" section
The Physical properties section of the article gives a laborious summary of various age estimates that are said to be for the Alpha Centauri system. As written, it is not clear if these apply to Proxima, though it seems that they do. More generally, can this tedious section be reduced a bit? Thanks, Attic Salt (talk) 15:26, 20 December 2018 (UTC)
 * See the next section of this talk page. The whole article is confused about when it is describing α Centauri as two sun-like stars in a close orbit and when it is describing α Centauri as a triple system including a very distant red dwarf.  In this case, I think the slightly long-winded age descriptions are appropriate in a highly detailed and complete article, but it should be clearer about the age of Proxima which is not being discussed here.  Lithopsian (talk) 20:18, 2 January 2019 (UTC)

Starbox
Why does the starbox mostly have information about Alpha Centauri AB? Shouldn't it also have information about Proxima Centauri as well? Sbznpoe (talk) 09:17, 2 January 2019 (UTC)
 * yes. It should. go for it. Cas Liber (talk · contribs) 10:05, 2 January 2019 (UTC)
 * Careful. There is a separate (featured) article for Proxima Centauri and we shouldn't try to reproduce it here.  The split between this article and Proxima Centauri is a bit messy after a split, and potentially always confusing since Proxima is part of a star system that we call α Centauri in its broadest sense, but the split was approved following discussion and shouldn't be reversed prematurely.  Actually, looking back, it seems that there wasn't discussion about a split, but there was unanimous agreement not to merge Proxima back here.  Lithopsian (talk) 15:19, 2 January 2019 (UTC)

Maybe the starbox could be renamed to Alpha Centauri AB and the little part about Proxima at the bottom could be removed. Sbznpoe (talk) 19:17, 2 January 2019 (UTC)
 * That might make the most sense given the separation of articles. Treat Alpha AB as a separate system than Proxima, with not much more than a footnote indicating Proxima's membership in the system. I will note, however, that the decision to not merge the articles took place before Proxima was known to definitively be bound to Proxima AB - it's only been the the past couple of years that the question has been firmly resolved. <b style="color:green">Tarl N.</b> ( discuss ) 19:57, 2 January 2019 (UTC)
 * Yes, I like this as well, Tarl. This article should focus on AB, but make it abundantly clear in a paragraph in the lead that Proxima is part of the whole system. — Huntster (t @ c) 22:12, 2 January 2019 (UTC)


 * I would suggest that the article is called Alpha Centauri, not Alpha Centauri system. Clearly, Proxima needs to be mentioned, probably frequently, but it is over two degrees away, invisible to the naked eye, not known when the Bayer designation was assigned, not known at all until 100 years ago, to all intents and purposes a separate object with a separate article that is never going to be merged here.  The term Alpha Centauri is very rarely used to refer to Proxima, the opportunity for confusion is limited unless we go out of out way to try and use that designation to include Proxima.  Yes it is, we now know almost certainly, gravitationally bound, but the Earth is gravitationally bound to the sun and we don't try to shoehorn it into the same article - just mention it, link it, and then largely forget about it.   Lithopsian (talk) 21:30, 2 January 2019 (UTC)

so....are we talking about the article or the starbox now? Either way, with the split of the Proxima article, people seem to say that this article (starbox included) should have less information on star C because there's another article on that. Sbznpoe (talk) 22:28, 2 January 2019 (UTC)
 * My suggestion would be for the starbox to say "Alpha Centauri AB" (as it looks like it has already been renamed), with a note (maybe in the final paragraph of the lead) saying that while bound to AB, detailed descriptions of C/Proxima and its planets are in another article. The article should stay named "Alpha Centauri". But that's an aesthetic opinion of one. <b style="color:green">Tarl N.</b> ( discuss ) 04:04, 3 January 2019 (UTC)
 * I certainly wouldn't want to change the article title; α Centauri has historically and in most contexts referred to the naked-eye close binary star, only including Proxima in a very few specific contexts. I'm not over-joyed about having AB in the starbox title, for that same reason and because α Centauri AB really isn't a title that's used very often, but if it helps to keep things clear in a slightly confusing situation then I can live with it.  Lithopsian (talk) 17:22, 3 January 2019 (UTC)
 * I was bold and added a footnote to the title "Alpha Centauri AB" in the starbox. Please revert if anyone sees any problems on having done so. Regards, <b style="color:green">Tarl N.</b> ( discuss ) 00:55, 4 January 2019 (UTC)

"Good" Article?
This is just a thought, but does anyone else think that this article is at least "good" quality now? Sbznpoe (talk) 04:25, 14 February 2019 (UTC)
 * It is still poorly sourced, and has been greatly diminished by novice edits with little understanding of astronomical conventions. GA is unlikely as it appears now. Arianewiki1 (talk) 23:40, 23 February 2019 (UTC)

Alpha Centauri Bc
The reference and statement that a possible other planet was found in 2013 is inaccurate. References 82 and 83 are actually the same Demory et al 2015 reference. The paper makes no mention anywhere of a 2013 announcement. Please remove the text "The existence of a planet, Alpha Centauri Bc, was announced in 2013. It has an estimated orbital period of approximately 12 Earth days – less than that of Mercury – with a semimajor axis of 0.10 AU and an eccentricity smaller than 0.24.[82]" Pcauchy (talk) 13:49, 28 February 2019 (UTC)

Whether stars of a high declination can be simply put in relative terms as lower/higher and then the other dimension (as we can view it, i.e. 2nd dimension) can be called 'offset'
(moved here from my personal talk page, in case anyone wishes to discuss it further, or edit this article accordingly Lithopsian (talk) 19:39, 28 May 2019 (UTC))

Firstly whilst I am enamoured of the complexity and finesse of greek and latin terms in science, there is nought wrong in my mind in calling a high northern or southern star (in those hemispheres) "above" / "below" another; indeed anything about say 10 degrees (probably 0 degrees) should be capable of being branded in that simple comparative way. To introduce ambiguity in your mind; sow the seeds of doubt is both ignorant and/or reticient and is frankly culturally supramacist; Anglo-Saxon and Norman based English is no less capable of describing things than sharp, wordy greek and latin forms which do not lend themselves to wider reading and frankly where never explained, and always wikilinked inject an unnecessary jargon tone into what is supposed to be an encyclopedia, not a robust academic essay. The other dimension can obviously be stated immediately after as 'offset' or are readers to be taken as never able to read words in their obvious context.- <b style="color: black">Adam37</b> Talk  17:15, 28 May 2019 (UTC)
 * Definitely try to avoid using above/below. Use north/south. One minor exception, "higher latitude" means "closer to the pole". As an aside, I compared the entire flurry of edits, I'm not seeing an improvement. Certainly the change in caption is a definite negative, and several other of the changes seem to be change for the sake of change, not helpful. I was tempted to revert the entire mess and suggest it all be discussed here. <b style="color:green">Tarl N.</b> ( discuss ) 21:00, 28 May 2019 (UTC)
 * 'High latitude' means the same as 'high declination': often understood between +60°N and the north pole or −60°S to the south pole.  Defined as: "one designated by the higher figures; consequently, a latitude remote from the equator." Low latitude is 30° either side of the equator.  This link explains this to Grade 6  like here above.
 * The context is obvious.
 * How this relates to possible prejudice issues is something you have to deal with. Take this advice, please. Arianewiki1 (talk) 06:17, 29 May 2019 (UTC)

Stellar system section
Apart from the first sentence, does the introductory paragraph to this section add anything useful to this article? Is it understandable? Is it even correct? Lithopsian (talk) 15:40, 17 January 2020 (UTC)
 * @Lithopsian, I think it's correct (at least the AB part) but in the wrong section. I think the information there would better fit in Nomenclature. It definitely needs to be rewritten for a general audience though, it's kinda wordy and dense. Supernova58 (talk) 21:36, 2 August 2020 (UTC)

Circumstellar discs
Should the "Circumstellar discs" subsection mention the false detection of discs around Proxima Centauri by ALMA in 2017? Supernova58 (talk) 21:14, 2 August 2020 (UTC)

why is "confirmed planets" blank?
the section "comfirmed planets" seems to be blank. 71.89.213.158 (talk) 05:50, 28 November 2020 (UTC)
 * It isn't. It contains the sections Proxima Centauri b and Proxima Centauri c. <b style="color:green">Tarl N.</b> ( discuss ) 05:54, 28 November 2020 (UTC)

Parallax, Observational History vs Kinematics sections
The discussion of Johnson, Henderson, and the discovery of proper motion and parallax is in conflict between para. 4 of Observational History, and para. 2 of Kinematics. The former reads as more informed, and thus likely more accurate, than the latter, but I leave it to those more familiar to make the judgement. Regardly, this needs fixing. It is ridiculous (literally) to have an article disagree with itself. 2001:56A:F0E9:9B00:BC7E:9A8:AECB:1970 (talk) 00:58, 1 December 2020 (UTC)JustSomeWikiReader
 * What exactly is the discrepancy? It seems like one refers to orbital elements within Alpha Centauri, the other refers to distance and proper motion. Either I'm looking at the wrong sections or the disagreement isn't obvious - please quote the pieces you think disagree. <b style="color:green">Tarl N.</b> ( discuss ) 01:16, 1 December 2020 (UTC)

Candidate 1
User:ExoEditor has created this article on the candidate planet at Alpha Centauri A. I'm not sure what to do with it, but it shouldn't be kept as is. It's certainly a notable topic, but as an unconfirmed planet candidate that was just recently announced, it's too soon for it to have its own article separate from this one. I'd just merge and redirect it here, but the title doesn't seem like a plausible redirect - "Candidate 1" probably refers to other things as well, and if the planet was confirmed, it would be called Alpha Centauri Ab. (Also, it currently reads more like a news release than an encyclopedia article.) SevenSpheresCelestia (talk) 23:37, 12 February 2021 (UTC)


 * I support this. I'd take some of the points from the actual article and add to the actual section under Unconfirmed Planets. TheWhistleGag (talk) 22:48, 27 February 2021 (UTC)

Alf Cen Bc impact parameter
This recent edit removes the claim that the planet candidate Alpha Centauri Bc has "an impact parameter of around 0–0.3" with the comment that Impact parameter < 1 means that a orbit is impossible so whatever the editor was saying needs some tweaks. Maybe excentricity? However, the paper supports this claim: [...] We find that the STIS photometry yields an orbital period 2-σ upper limit of 20.4 days (the median of the posterior being 12.4 days), with a modest impact parameter ∼ 0.0 − 0.3 and an eccentricity 2-σ upper limit of 0.24. I don't think this precludes the existence of the planet either, given that the NASA Exoplanet Archive lists over 3000 planets with an impact parameter < 1. SevenSpheresCelestia (talk) 00:00, 16 February 2021 (UTC)

A organizational Suggestion
For stellar system, can we organize physical properties of the three stars into a table? It might help with reading and comparing the stars. Nchen269 2:16, 9 May 2021 (UTC)

Changing "Ab" to "C1" in Alpha Cen A's planetary orbitbox?
I was looking at the planetary orbitbox for Alpha Centauri A and noticed that it had an "Ab" exoplanet present. However, the potential planet is mentioned in the surrounding section as C1 ("Candidate 1"), the name used in the discovery paper. I feel this may be slightly confusing to readers, possibly giving the impression that "Alpha Cen Ab" and "C1" are separate objects. I'm thinking of replacing the "Ab" designation in the orbitbox with "C1" - I would use a note to mention that the planet will likely one day receive the "Ab" designation pending further observations (but has not yet). Please let me know what you think of this proposal. Thanks for considering! Supernova58 (talk) 01:55, 24 July 2021 (UTC)
 * The name c1 is a purely temporary name for a hypothetical possible uncertain (add a few more qualifiers) detection. Ab would be the official name of the first detected planet of Alpha A. Don’t attempt to make c1 more prominent, if it gets confirmation it will get a real name. <b style="color:green">Tarl N.</b> ( discuss ) 03:41, 24 July 2021 (UTC)
 * Makes sense! I understood that C1 is not a real name, I just like to try to make articles as clear as possible! I see where that might promote the idea of C1 being official though (although it is not). In that case, I'll just add a sentence to the section itself to clarify any confusion - I'll mention that C1 is a temporary name and that Ab is (as of now) the name it will receive if confirmed, following convention. Thanks for your feedback! Supernova58 (talk) 04:05, 24 July 2021 (UTC)

Requesting general thoughts/suggestions on the article
Hello everyone! I noticed that this article is rated as B-class. Considering its high importance rating, I think it should be made a GA as soon as possible. However, it's not there yet - it failed the last nomination. I'm asking anyone who's read this article (or contributed to it) to put their suggestions below. For example, I think the planetary system section is a little clunky. The more suggestions posted, the better chance we all have of eventually upgrading this article to GA-candidate material! Supernova58 (talk) 02:48, 9 August 2021 (UTC)

I like the article, not clunky. Gives a lot of pics and scientific data. Also a question - Would Alpha Centauri be the first system that we visit once we are able to travel at light speed?


 * Since we will almost surely never be "able to travel at light speed", that would be a no.2601:41:200:5260:2D36:29AC:1099:E53B (talk) 21:24, 8 September 2021 (UTC)

worth adding an "in popular culture" section?
can think of quite a few notable cultural works that heavily feature Alpha Centauri. Likeanechointheforest (talk) 21:59, 25 October 2021 (UTC)
 * Alot of people hate those sections. Best way is to find some secondary source that discusses various appearances/references to Alpha Centauri. There is also Stars and planetary systems in fiction, where almost all of this content got diverted to about 15 years ago. Cas Liber (talk · contribs) 22:05, 25 October 2021 (UTC)
 * Oops - found Alpha Centauri in fiction (note this is a huge list of primary sources....) Cas Liber (talk · contribs) 22:09, 25 October 2021 (UTC)