Rho Capricorni

Rho Capricorni (ρ Cap, ρ Capricorni) is a binary star in the constellation Capricornus. Sometimes, this star is called by the name Bos, meaning the cow in Latin. 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. Consequently, the Chinese name for ρ Capricorni itself is 牛宿六 (Niú Su liù, the Sixth Star of Ox.)

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

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