Eta Capricorni

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Eta Capricorni
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Capricornus
Right ascension 21h 04m 24.301s[1]
Declination –19° 51′ 17.97″[1]
Apparent magnitude (V) +4.82
Spectral type A4V + F7/8V[2]
Proper motion (μ) RA: –37.62 ± 0.90[1] mas/yr
Dec.: –24.95 ± 0.88[1] mas/yr
Parallax (π) 19.49 ± 0.29[2] mas
Distance 167 ± 2 ly
(51.3 ± 0.8 pc)
Other designations
HD 200499, HR 8060, BD–20°6115, HIP 104019, SAO 189986, WDS J21044-1951AB[3]

Eta Capricorni (η Cap, η Capricorni) is a binary star in the constellation Capricornus. It is approximately 167 light years from Earth.

The primary component, η Capricorni A, is a white A-type main sequence dwarf with an apparent magnitude of +4.82. Its companion, η Capricorni B, has an apparent magnitude of +6.5 and is located 0.34 arcseconds from the primary.

Sometimes, this star is called by the name Armus.[4]

Chinese Name[edit]

In Chinese, 十二國 (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.[5] Consequently, η Capricorni itself is known as 周一 (Zhou yī, English: the First Star of Zhou), meaning that this star (together with 21 Capricorni and β Serpentis in Right Wall of Heavenly Market Enclosure (asterism)[6][7]) represent Zhou () (possibly Chow, the dynasty in China).[8]