# Talk:Albireo

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## Period

I've taken out the phrase about the distance and orbital period of the binary system, since I've found pages saying that the distance between pair stars is 4400 AU with orbital period of 7300 earth year, such as [1]. --Puzzlet Chung 06:58, 20 Mar 2005 (UTC)

Something is not right with these numbers. Kepler's third law can be expressed as ${\displaystyle a^{3}=(m_{1}+m_{2})P^{2}}$. If we give a total mass of, say, 10 Suns, orbital period of the stars would be still about 92000 years. But in the original article, distance was 44 AU, which is wrong. In that case orbital period would be much less than Pluto's. This article [2] gives possible orbital period of 7800 years. --Jyril 09:04, Mar 20, 2005 (UTC)

## Triple

I replaced the section on Albireo as a triple star -- I was some years later and for several years a member of the team which had made the first high-precision measurements in 1976, and made some of the circa 1990 observations myself using the Kitt Peak 4m telescope. The catalogue of interferometric observations by all groups of this object (and all other binary stars) may be found in the Fourth Catalog of Interferometric Measurements of Binary Stars, available at the US Naval Observatory, http://ad.usno.navy.mil/wds/int4.html. -- Don Barry, Cornell University (24.92.255.115 on 26 September 2006)

## Orbital elements

This page contains nonsense. There is absolutely no source for the orbital elements (eccentricity, longitude of node, orbital period, separation, etc., etc.). The Washington Double Star Catalog quoted as the source lists all components of the albireo system; it lists no orbital elements. the sixth orbital catalog lists elements only for the spectroscopic Ab,Ac system. At a period of 220,000 years there is no way humanity has in two centuries amassed enough positional change data to compute orbital elements. All these numbers have been made up whole cloth. Macevoy (talk) —Preceding undated comment added 21:35, 24 April 2012 (UTC).

The problem is that the infobox is displaying orbital data for Albireo C, not Albireo B. Is there any way to specify this in the infobox? Should the orbital section be removed from the infobox since it gives the impression that the data is for Albireo B? UPDATE: Under "orbit_footnote" I have added, " for Albireo C" to hopefully make the infobox clearer and less misleading. -- Kheider (talk) 19:15, 17 September 2012 (UTC)
The pair visible in a small telescope is A/B. The pair of stars in the first infobox is Aa/Ac, which is also the pair for which the orbit is given. B is in the second infobox, lower down. Spacepotato (talk) 03:43, 18 September 2012 (UTC)
I disagree. As far as I know, the apparent magnitude of 5.8 is Albireo B (the distant blue-green start) not C (the close star). I have corrected this in the infobox.
Obviously, the infobox is not optimal at present, with parts of it referring to the larger binary system, and others to the smaller. Whoever reads this, please feel encouraged to improve ... Tomeasy T C 23:00, 7 November 2014 (UTC)
The first infobox refers to Aa/Ac, the close spectroscopic binary, and the second to B, the more distant companion. See the Washington Double Star Catalog [3], entry 19307+2758. Spacepotato (talk) 23:37, 7 November 2014 (UTC)

## Distances

1.: Distance from earth: The article says "380 light-years (120 pc)" and the infobox says "430 ± 20 ly (133 ± 6 pc)". Now what?
2.: It seems User:PuzzletChung removed the distance from one star to the other in 2005. It's a shame that no one has been able to fill this in in the meantime. I would do the calculation myself if not for 1.
I help out as a guide at an observatory, and thats the first thing people ask: "How far away ist it" / "How much distance between the two". I came here today to get answers, and I'm quite surprised that apparently no one has been able to provide these yet. --BjKa (talk) 17:09, 1 November 2012 (UTC)

380 is an old value, I believe from the original Hipparcos parallax. The revised Hipparcos parallax gives 430. Note that Albireo B infoxbox still has the old value, hence it is 40 light years from its primary :) Interestingly, the new Hipparcos reduction gives different values for the parallaxes of Alibireo A and B, slightly larger than their joint margins of error, an interesting comment on the accuracy of such things. Fixing. Lithopsian (talk) 17:30, 1 November 2012 (UTC)

## Pronunciation

Could someone put up a sound file as I am not sure how to pronounce it? Jzlcdh (talk) 13:54, 15 July 2013 (UTC)

## Discovering a binary with an interferometer?

The article states: "In 1976, component A was itself discovered to be a binary star, using speckle interferometry and the 2.1-meter telescope at the Kitt Peak National Observatory." This seemed suspicious since determining the binary nature of a star with a spectroscope is generally easier than resolving the pair with an interferometer. So I checked and found that Albireo Aa and Albireo Ac, the pair in question, have separate Henry Draper Catalog numbers, HD 183912 and HD 183913 respectively. They must have been known as a spectoscopic binary pair since 1949 at the latest, the last year that the HDC was updated. So, what happened in 1976 was that a known spectoscopic binary was resolved by interferometry. I will make the appropriate correction when I can get the wording and references right, if someone else does not beat me to it. - Fartherred (talk) 18:24, 27 February 2015 (UTC)

In general there is no guarantee that a binary can be detected spectroscopically. Gowever, Albireo has been known to have a composite spectrum for at least a century. Although one of the speckle references claims that no radial velocity differences had ever been detected, the radial velocity of Albireo A had been reported as early as 1919 to be decreasing slowly. It is now known to be a long period binary directly resolvable by modern equipment. Lithopsian (talk) 20:12, 27 February 2015 (UTC)
Thanks Lithopsian, I should have written that determining the binary nature of a star with a spectroscope is easier than resolving the pair with an interferometer most of the time. Of course there are cases in which the axis to rotation of the binary is parallel to the line of sight. With modern spectroscopy and the high orbital speeds that can be involved, there is a small fraction of cases in which the binary nature of a star eludes the spectroscope. Uncountable binaries are beyond resolution with an interferometer. In this case the binary nature of Albireo A was known long before 1976, as shown by the HD numbers, and that is what is most significant here.
Another point about the article, the font in the infobox makes the seconds mark in +27° 57′ 34.84″ for the declination of Aa practically illegible on my display. I had to copy it to a larger font to be sure of the text and then just remember what was printed where.- Fartherred (talk) 21:56, 27 February 2015 (UTC)
Albireo Aa and Albireo Ac orbit each other in 213 years. The separation I calculate from the infobox is 0h 0m 0.009s right ascension and 0° 0′ 0.22″ declination. However the separation given on this site is 0.4 arc seconds. If the separation is decreasing it could be near minimum now which would likewise make the radial velocity differences minimum. One could wait fifty-six years to make spectroscope measurements or else read the literature to find what the spectrum differences were when one could detect them. Various websites copy free information with questionable reliability but I hope professional astronomers have access to historical data that they can depend upon. - Fartherred (talk) 22:47, 27 February 2015 (UTC)
I have made the correction. If someone can improve the wording and give better references, feel free. - Fartherred (talk) 15:47, 1 March 2015 (UTC)

# ==

Also known as the Cub Scout star; but I'm not too sure how to edit it in without it looking like an abomination. :( — Preceding unsigned comment added by 104.220.56.173 (talk) 01:15, 7 July 2016 (UTC)