Chi Ursae Majoris
Chi Ursae Majoris or χ Ursae Majoris, formally named Taiyangshou, is a single star in the northern circumpolar constellation of Ursa Major. The star has an orange hue and is visible to the naked eye at night with an apparent visual magnitude of 3.72. It is located at a distance of approximately 198 light-years from the Sun based on parallax, but is drifting closer with a radial velocity of −9 km/s.
Nomenclature
χ Ursae Majoris is the star's Bayer designation.It bore the traditional name Taiyangshou, meaning Guard of the Sun, from Chinese astronomy. It is a single-star asterism in the Purple Forbidden enclosure. In R. H. Allen's Star Names, this name was transliterated as Tai Yang Show, "the Sun Governor". The star has also been called Alkafzah, Al Kaphrah, or El Kophrah, from Arabic القفزة al-qafzah "the leap ", which refers to an asterism consisting of ι, κ, λ, μ, ν, and ξ Ursae Majoris.
In 2016, the IAU organized a Working Group on Star Names to catalog and standardize proper names for stars. The WGSN approved the name Taiyangshou for this star on 30 June 2017 and it is now so included in the List of IAU-approved Star Names. The name Alkaphrah was approved for κ Ursae Majoris.
Properties
Chi Ursae Majoris is an evolved, orange hued K-type giant with a stellar classification of K0.5 IIIb. It is a red clump giant, which means it is on the horizontal branch and is generating energy through helium fusion at its core. This star has expanded to 23 times the radius of the Sun with 1.49 times the Sun's mass. It is radiating 170 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,331 K.The spiral galaxy in Ursa Major, NGC 3877, type Sc, is best found from Chi Ursae Majoris, which is almost exactly 15 arcminutes north of the galaxy.