# Talk:61 Cygni

61 Cygni has been listed as one of the Natural sciences good articles under the good article criteria. If you can improve it further, please do so. If it no longer meets these criteria, you can reassess it.
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## Talk 1

The planet around 61 Cygni B was first reported in the 1890s by the American astronomer Thomas J. J. See (1867-1960), then at the Leander McCormack Observatory. See specialized in studying binary stars to determine their orbits, and it was the gravitational effect of this planet on the motion of 61 Cyg B that led him to submit an article claiming a third object in the 61 Cyg system. He did not claim a planet, but any astronomer checking his figures could see this was no star. The resultant controversy effectively destroyed See's career, and he was forced to leave his post. He wound up doing mathematical work for the Naval Observatory, and long outlived his foes.

If this is true, it belongs in the article, not on the talk page. The Singing Badger 13:47, 26 Nov 2004 (UTC)
If 61 Cygni really has a planet, then why it is not in the Extrasolar Planets Encyclopaedia? All the old planet "discoveries" by astrometry have been disproven, because the observations were way too imprecise (radial velocity surveys could have spotted them). Only one planet have been confirmed astrometrically so far (Gliese 876 b) by Hubble Space Telescope.
Note that there is another star in a binary system, 16 Cygni B that indeed has a very eccentric planet. Jyril 14:07, 27 Nov 2004 (UTC)
I just realised you're right, I mistook 16 Cygni for 61 Cygni. What a berk I am! Sorry... The Singing Badger 18:05, 27 Nov 2004 (UTC)
I've heard of this 61 Cyg B too, so I agree that this story shall be in the article under a "history" section, that could also refer to Bessel's parallax measurements. Since the dist to 61 Cyg was measured before dist to α Cen, 61 was for a while the nearest known star. 61 Cyg lacks a name, but if any, it should be known as Bessel's star (but don't write that in the article). Rursus 12:20, 16 December 2006 (UTC)
In fact, a google for Bessel's Star gives a few hits pointing to 61 Cygni, so it might actually be referred to as Bessel's Star. Rursus 12:24, 16 December 2006 (UTC)

## Talk 2

The mention that there might be a planet of 61 Cygni is unsourced in the article and rather inprecise. If it is only a dubious and decades out-of-date claim then that should be noted. In any event references should be given. From 61 Cygni 2, I have links to this 1943 paper claiming a planet, this 1957 paper also claiming one and a 1978 paper attempting to refute such claims. MichaelSH 19:13, 1 October 2006 (UTC)

The statement "From the point of the view of the casual astronomical observer, 61 Cygni is not particularly spectacular." seems to me to be a matter of opinion and therefore does not belong here. I think it should be deleted unless someone seriously objects and can cite a verifiable source for the statement. Chris 19:25, 10 August 2006 (UTC)

This is from page 302 of the book "The Nine Planets" (copyright 1970) "Of course, the theories of cosmology do not prove that other solar systems exist. But in recent years other convincing evidence has appeared to indicate that they do. For those who were heartily eager to believe that other solar systems might someday be found as possible repositories of intelligent life, the most encouraging discovery imaginable has been made in recent years: at least two other stars have been shown definitely to have at least one planet apiece. And for a race of creatures about to leap into space and explore their own solar system, that discovery has breathtaking significance. Granted that no one yet has actually seen a planet of another star. The star systems involved are 61 Cygni and 70 Ophiuchi. Both of these are double-star systems and are close enough to be observed and studied fairly well. In each case, astronomers observed that the two stars in the binary systems were not moving around each other in quite the fashion they ought to be. Their orbits deviated a tiny bit from the expected pattern. With no other factors that could possibly be causing such deviations, only one explanation was possible. In each of these systems the "A" and "B" components (the double stars that could be seen) were being influenced by a dark "C" component. In either case it was possible to calculate the characteristics of such a "C" component. It would have to be another stellar or planetary body, but not a very large one because its influence on the "A" and "B" components was very small. The observers concluded that the "C" component in the 61 Cygni system was a dark mass of matter with approximately the weight of sixteen Jupiters, while in 70 Ophiuchi the "C" component was a nonluminous body with the mass of ten and one-half Jupiters." (User: Zachariahskylab)

## Moon width in 150 years?

The net proper motion μ of 61 Cygni is:

${\displaystyle \ ={\sqrt {\mu _{\delta }^{2}+\mu _{\alpha }^{2}\cdot \cos ^{2}\delta }}}$
${\displaystyle \ ={\sqrt {4109.17^{2}+4156.93^{2}\cdot \cos ^{2}38.74^{\circ }}}}$
${\displaystyle \ =5234.34}$ mas.

The Moon is about a half-degree across, or ~1,800 arc seconds. So 61 Cygni will traverse the diameter of the Moon in ${\displaystyle 1800/5.2=346}$ years. I am wondering where the 150 year figure came from. Any ideas? — RJH (talk) 19:03, 24 July 2007 (UTC)

No response to this, so I removed the statement from the article. — RJH (talk) 20:23, 4 September 2007 (UTC)

The change in declination is 3259.39 mas per year, not 4109.17. —Preceding unsigned comment added by 77.127.10.172 (talk) 11:45, 10 September 2009 (UTC)

True.
${\displaystyle {\sqrt {3259.39^{2}+4156.93^{2}\cdot \cos ^{2}38.74^{\circ }}}}$
${\displaystyle \ =4909.38}$ mas.
1800/4.9 = 367 years.—RJH (talk) 17:59, 10 September 2009 (UTC)

## Successful good article nomination

I am glad to report that this article nomination for good article status has been promoted. This is how the article, as of October 3, 2007, compares against the six good article criteria:

1. Well written?: A thorough and enjoyable read. I thought the bottom of the article could use tightening a bit though, it just sort of ended.
2. Factually accurate?: I am a layman so may not be the best person to check that but all the references I checked seemed to test out.
3. Broad in coverage?: Seemed quite thorough. Some suggestions: Are there any future plans for study? or long term implications of what was learned so far? Where is the proper motion taking this pair? When will it get there?
4. Neutral point of view?: Very. A no brainer.
5. Article stability? Seems quite stable, no sign of edit wars. Signs that a few dedicated editors have worked hard over the years to polish this nicely.
6. Images?: Two good images. I found the relative size one informative. The star map I found a bit confusingly labeled... are both black spots 61 Cygni? Is there a locator for where Cygni is in the stellar sphere that could be added?

If you feel that this review is in error, feel free to take it to Good article reassessment. Thank you to all of the editors who worked hard to bring it to this status, and congratulations. — ++Lar: t/c 01:39, 3 October 2007 (UTC)

Thank you for the review and the feedback. — RJH (talk) 17:36, 6 October 2007 (UTC)

## 16 Cygni

Do we really need to mention that "61 Cygni" should not be confused with "16 Cygni" in the lead? I'm not clear what value, if any, that paragraph provides. It is also unsourced. At most a hatnote should suffice.—RJH (talk) 18:39, 23 September 2008 (UTC)

## Parallax

The parallax of the star is given as 287.18 ± 1.51[1] mas, where mas links to minutes of arc. Shouldn't it be milliarcseconds instead? 202.129.234.249 (talk) 06:17, 20 April 2010 (UTC)

I think this is a case of articles being merged. The milliarcsecond link redirects to the minutes of arc article. If you look on the minutes of arc article, it covers milliarcseconds.—RJH (talk) 17:06, 20 April 2010 (UTC)

## AU or au?

The international standard symbol for astronomical unit is au, not AU. It is confusing to introduce a non-standard symbol. Dondervogel 2 (talk) 18:54, 16 June 2015 (UTC)

Rather, "AU" is by far the more commonly used, both in scientific publications and in more-popular astronomical writing, which makes "au" the confusing symbol, regardless of the official sanction. But you know that already. I don't know why you now insist on "au" when earlier you were okay with "AU", as long as it was used consistently. --JorisvS (talk) 19:27, 16 June 2015 (UTC)
I am OK with any symbol, including AU, for which there is consensus, but despite several attempts, consensus seems beyond our grasp. I do not understand the objections raised at MOSNUM to this choice, but until such time as agreement is reached there I will continue to argue that Wikipedia should follow international standard symbols, which in this case means au, not AU. I do agree that AU is more common, but I completely reject the suggestion that it is clearer. Does this help clarify? Dondervogel 2 (talk) 19:48, 16 June 2015 (UTC)
Yes, it does. But if the majority of the readers is (much) more familiar with "AU" than "au", how would "AU" not be clearer? --JorisvS (talk) 20:18, 16 June 2015 (UTC)
For exactly the same reason that Mbit/s is clearer than Mbps. The former is defined by international agreement. The latter is not. In the absence of guidance from MOSNUM the natural way of defining any symbol is to follow the appropriate international standards body, which in the case of the au is the IAU, with the support of BIPM. Dondervogel 2 (talk) 20:50, 16 June 2015 (UTC)
But Mbit/s has the common "/" for "per", whereas Mbps has the uncommon "p". No such decomposition is possible with either "au" or "AU". --JorisvS (talk) 21:04, 16 June 2015 (UTC)
The issue of whether one or other symbol or part of symbol is common does not come into it. My argument is entirely about whether something "exists", in the sense that it is defined by a an authoritative body. For WP that authoritative body is MOSNUM. (Yes I know it is a guideline, but it is an authoritative guideline). For as long as AU remains undefined, I cannot support it as a symbol for anything, and will continue to argue against it on those grounds. Dondervogel 2 (talk) 21:54, 16 June 2015 (UTC)
No matter that "AU" is more common (which more to whether it "exists" than any formal recommendation) and a number of editors have indicated that it is easier for them to understand "AU" than "au"... I don't see the logic in that. --JorisvS (talk) 08:50, 17 June 2015 (UTC)
What an editor says and what (s)he means are sometimes two different things. In this case I suspect they confuse familiarity (what they mean) with clarity (what they say). Just my opinion, of course. I just typed something similar, with better explanation, in my response to Ashill on MOSNUM.Dondervogel 2 (talk) 09:00, 17 June 2015 (UTC)
From how I read it, they find "AU" much clearer because they are much more familiar with it (e.g. being familiar with the unit and having read a lot of texts that use "AU" for it, but few, if any that use "au" for it). Ashill has actually explained this rather nicely. --JorisvS (talk) 09:29, 17 June 2015 (UTC)