| absmag_v = +1.35[11]
}}{{Starbox orbit
| reference = [12]
| period = {{Val|27.85|0.15}}
| axis = {{Val|0.265|0.003}}
| eccentricity = {{Val|0.410|0.005}}
| inclination = {{Val|162.6|0.5}}
| node = {{Val|171.1|15.0}}
| periastron = {{Val|2002.46|0.09}}
| periarg = {{Val|238.2|15.0}}
}}{{Starbox detail
| source =
| component1 = η Cap A
| mass = {{Val|2.03|0.12}}[12]
| radius =
| luminosity = 24[11]
| temperature =
| gravity =
| metal_fe = −0.01[11]
| rotational_velocity =
| age_myr =
| component2 = η Cap B
| mass2 = {{Val|1.21|0.07}}[12]
}}{{Starbox catalog
| names = η Cap, 22 Cap, BD−20° 6115, HD 200499, HIP 104019, HR 8060, SAO 189986, WDS J21044-1951AB[17]
}}{{Starbox reference
| Simbad = eta+Cap
}}{{Starbox end}}Eta Capricorni, Latinized from η Capricorni, is a binary star[12] system in the southern constellation of Capricornus. It can be seen with the naked eye, having a combined apparent visual magnitude of +4.84.[3] Based upon an annual parallax shift of 20.20 mas as seen from the Earth,[ the star is located about 161 light years from the Sun.]
The pair orbit each other with a period of 27.85 years, a semimajor axis of 0.265 arc seconds, an eccentricity of 0.410.[12] The primary member, component A, is a white-hued A-type main sequence star with an apparent magnitude of +5.02.[4] Its companion, component B, has an apparent magnitude of +7.39.[4]
Nomenclature
η Capricorni (Latinised to Eta Capricorni) is the system's Bayer designation. It also has the Flamsteed designation 22 Capricorni.
In Chinese, {{lang|zh|十二國}} ({{lang|zh-Latn|Shíer Guó}}), meaning Twelve States, refers to an asterism which is represent twelve ancient states in the Spring and Autumn period and the Warring States period, consisting of η Capricorni, φ Capricorni, ι Capricorni, 38 Capricorni, 35 Capricorni, 36 Capricorni, χ Capricorni, θ Capricorni, 30 Capricorni, 33 Capricorni, ζ Capricorni, 19 Capricorni, 26 Capricorni, 27 Capricorni, 20 Capricorni and 21 Capricorni.[1] Consequently, η Capricorni itself is known as {{lang|zh|周一}} ({{lang|zh-Latn|Zhou yī}}, {{lang-en|the First Star of Zhou}}), meaning that this star (together with 21 Capricorni and β Serpentis in Right Wall of Heavenly Market Enclosure (asterism)[2]) represent Zhou ({{lang|zh|周}}) (possibly Chow, the dynasty in China).[26]
Sometimes, this star is called by the name Armus in an astrological context.[27]
References
1. ^{{zh icon}} 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, {{ISBN|978-986-7332-25-7}}.
2. ^{{cite web|url=http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Serpens*.html|title=LacusCurtius • Allen's Star Names — Serpens|publisher=}}
3. ^1 2 3 {{citation | title=XHIP: An extended hipparcos compilation | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015 | arxiv=1108.4971 | postscript=. }}
4. ^1 2 3 {{citation | last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A. | title=A catalogue of multiplicity among bright stellar systems | journal=Monthly Notices of the Royal Astronomical Society | volume=389 | issue=2 | pages=869–879 | date=September 2008 | doi=10.1111/j.1365-2966.2008.13596.x | bibcode=2008MNRAS.389..869E | arxiv=0806.2878 | postscript=. }}
5. ^1 2 3 4 {{citation | author1=Nicolet | first1=B. | title=Catalogue of homogeneous data in the UBV photoelectric photometric system | journal=Astronomy and Astrophysics | volume=34 | pages=1 | year=1978 | bibcode=1978A&AS...34....1N | postscript=. }}
6. ^1 {{citation | title=Binary Star Differential Photometry Using the Adaptive Optics System at Mount Wilson Observatory | display-authors=1 | last1=ten Brummelaar | first1=Theo | last2=Mason | first2=Brian D. | last3=McAlister | first3=Harold A. | last4=Roberts | first4=Lewis C., Jr. | last5=Turner | first5=Nils H. | last6=Hartkopf | first6=William I. | last7=Bagnuolo | first7=William G., Jr. | journal=The Astronomical Journal | postscript=. | volume=119 | issue=5 | pages=2403–2414 | date=May 2000 | doi=10.1086/301338 | bibcode=2000AJ....119.2403T }}
7. ^1 2 3 4 5 {{citation | title=Dynamical and physical properties of 22 binaries discovered by W. S. Finsen | last1=Docobo | first1=J. A. | last2=Andrade | first2=M. | journal=Monthly Notices of the Royal Astronomical Society | volume=428 | issue=1 | pages=321–339 | year=2013 | postscript=. | bibcode=2013MNRAS.428..321D | doi=10.1093/mnras/sts045 }}
8. ^1 {{cite simbad | title=eta Cap | accessdate=2017-05-15 | postscript=. }}
9. ^1 {{citation | url=http://www.constellationsofwords.com/stars/Armus.html | title=Armus | publisher=constellationsofwords.com | accessdate=2017-05-16 | postscript=. }}
10. ^1 {{citation | url=http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Capricornus*.html | first1=Richard Hinckley | last1=Allen | publisher=Dover | year=1963 | accessdate=2017-05-09 | title=Star Names, Their Lore and Meaning | chapter=Capricornus | postscript=. }}