Editing 61 Cygni (section)

=== Binary observations ===
Due to the wide angular separation between 61 Cygni A and B, and the correspondingly slow orbital motion, it was initially unclear whether the two stars in the 61 Cygni system were a  [[star system|gravitationally bound system]] or simply a [[optical binary|juxtaposition of stars]].<ref name="davis-1898">{{cite journal
 | last=Davis | first=Merhan S.
 | title=Remarks regarding the parallaxes of 61 Cygni and the probable physical connection of these two stars
 | journal=Astrophysical Journal
 | date=1898 | volume=8 | pages=246–247
 | bibcode=1898ApJ.....8..246D
 | doi=10.1086/140527 | doi-access=free
 }}</ref> von Struve first argued for its status as a binary in 1830, but the matter remained open.<ref name="davis-1898" />

However, by 1917 refined measured parallax differences demonstrated that the separation was significantly less.<ref>{{cite journal
 | author=Adams, W. S.
 | author2=Joy, A. H.
 | title=The luminosities and parallaxes of five hundred stars
 | journal=Astrophysical Journal
 | date=1917 | volume=46 | pages=313–339 | bibcode=1917ApJ....46..313A
 | doi = 10.1086/142369
}}—See Table I, page 326</ref> The binary nature of this system was clear by 1934, and [[orbital elements]] were published.<ref>{{cite journal
 | last=Baize | first=P.
 | title=Second catalogue d'orbites d'Etoiles Doubles visuelles
 | trans-title=Second catalog of orbits of visual double stars
 | journal=Journal des Observateurs
 | date=1950 | volume=33 | pages=1–31 | language=fr | bibcode=1950JO.....33....1B
}}—on page 19, the authority is listed as Zagar (1934).</ref>

In 1911, [[Benjamin Boss]] published data indicating that the 61 Cygni system was a member of a [[Comoving distance|comoving]] group of stars.<ref>{{cite journal
 | last=Boss | first=Benjamin
 | title=Community of motion among several stars of large proper-motion | journal=Astronomical Journal
 | date=1911 | volume=27 | issue=629 | pages=33–37
 | bibcode=1911AJ.....27...33B
 | doi=10.1086/103931 }}</ref> This group containing 61 Cygni was later expanded to include 26 potential members. Possible members include [[Beta Columbae]], [[Pi Mensae]], [[14 Tauri]] and [[68 Virginis]]. The space velocities of this group of stars range from 105 to 114&nbsp;km/s relative to the Sun.<ref>{{cite journal
 | last = Eggen | first = O. J.
 | title=White dwarf members of the 61 Cygni group
 | journal=The Observatory
 | date=1959 | volume=79 | pages=135–139
 | bibcode=1959Obs....79..135E }} – Gives space velocity components of U=+94, V=–53 and W=–7 for HD 201091/2.</ref><ref>{{cite web | url=http://www.solstation.com/stars2/pimensae.htm | title=System Summary Pi Mensae | publisher=Sol Company | access-date=1 May 2015 | author=Sol Company | archive-date=3 June 2012 | archive-url=https://web.archive.org/web/20120603142304/http://www.solstation.com/stars2/pimensae.htm | url-status=live }}</ref>

Observations taken by planet search programs show that both components have strong linear trends in the [[radial velocity]] measurements.<ref name="howard-2016" />