Rho Ursae Majoris
Rho Ursae Majoris is the Bayer designation for a solitary star in the northern circumpolar constellation of Ursa Major. It is often faintly visible to the naked eye with an apparent visual magnitude of 4.74. The distance to this star, based upon an annual parallax shift of 10.37 mas, is around 315 light years.
With a stellar classification of M3 III, this is a red giant star on the asymptotic giant branch. It is a suspected small amplitude variable. The measured angular diameter of the star after correcting for limb darkening is, which, at the estimated distance of this star, yields a physical size of about 58 times the radius of the Sun. It is radiating 464 times the solar luminosity from its outer atmosphere at an effective temperature of about 3,725 K. Based upon its motion through space, there is a 60.6% chance that this star is a member of the Sirius stream.
Naming
- With π1, π2, σ1, σ2, A and d, it composed the Arabic asterism Al Ṭhibā᾽, the Gazelle. According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Ṭhibā were the title for seven stars : A as Althiba I, π1 as Althiba II, π2 as Althiba III, this star as Althiba IV, σ1 as Althiba V, σ2 as Althiba VI, and d as Althiba VII
- In Chinese, 三師, meaning Three Top Instructors, refers to an asterism consisting of ρ Ursae Majoris and σ2 Ursae Majoris. Consequently, the Chinese name for ρ Ursae Majoris itself is 三師一.