Rho Capricorni

Rho Capricorni (ρ Cap, ρ Capricorni) is a binary star^[3] in the constellation Capricornus. Sometimes, this star is called by the name Bos, meaning the cow in Latin.^[10] In Chinese, 牛宿 (Niú Su), meaning Ox (asterism), refers to an asterism consisting of β Capricorni, α² Capricorni, ξ² Capricorni, π Capricorni, ο Capricorni and ρ Capricorni.^[11] Consequently, the Chinese name for ρ Capricorni itself is 牛宿六 (Niú Su liù, English: the Sixth Star of Ox.)^[12]

Rho Capricorni

Location of ρ Capricorni (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Capricornus
Right ascension	20h 28m 51.61448s[1]
Declination	−17° 48′ 49.2693″[1]
Apparent magnitude (V)	+4.78[2] (4.97 + 6.88)[3]
Characteristics
Spectral type	F2 IV[2] + G1[4]
Astrometry
Radial velocity (Rv)	+18.4[5] km/s
Proper motion (μ)	RA: −14.98[1] mas/yr Dec.: −7.29[1] mas/yr
Parallax (π)	33.04±0.46 mas[1]
Distance	99 ± 1 ly (30.3 ± 0.4 pc)
Absolute magnitude (MV)	2.52 + 4.56[4]
Orbit[3]
Period (P)	278 yr
Semi-major axis (a)	1.877″
Eccentricity (e)	0.91
Inclination (i)	113.3°
Longitude of the node (Ω)	162.0°
Periastron epoch (T)	1965.0
Argument of periastron (ω) (secondary)	144.5°
Details[6]
ρ Cap A
Mass	1.52±0.04 M☉
Radius	1.3[2] R☉
Luminosity	9[7] L☉
Surface gravity (log g)	4.02±0.03 cgs
Temperature	6,911±63 K
Metallicity [Fe/H]	−0.20±0.05 dex
Rotational velocity (v sin i)	87.7[8] km/s
Age	1.74±0.15 Gyr
Other designations
ρ Cap, 11 Cap, ADS 13887, BD−18°5689, Gl 791.1, GJ 9696, HD 194943, HIP 101027, HR 7822, SAO 163614, WDS J20289-1749AB[9]
Database references
SIMBAD	ρ Cap
	ρ Cap A
	ρ Cap B
ARICNS	ρ Cap A
	ρ Cap B

This system is visible to the naked eye with a combined apparent visual magnitude of +4.78.^[2] The pair orbit each other with a period of 278 years and an eccentricity of 0.91.^[3] Based upon an annual parallax shift of 33.04 mas as seen from the Earth,^[1] the system is located about 99 light years from the Sun. It is a thin disk population^[6] star system that made its closest approach to the Sun about 1.6 million years ago when it came within 12.49 ly (3.830 pc).^[13]

The primary member, component A, is a yellow-white hued, F-type subgiant with an apparent magnitude of 4.97^[3] and a stellar classification of F2 IV.^[2] This star has 1.5^[6] times the mass of the Sun and 1.3 times the Sun's radius. It is radiating 9 times^[7] as much luminosity of the Sun from its outer atmosphere at an effective temperature of 6,911 K.^[6] The companion, component B, has a visual magnitude of 6.88.^[3] The mass ratio is 0.539, meaning the secondary is only 53.9% as massive as the primary.^[14]