Phi_Ursae_Majoris
Phi Ursae Majoris
Binary star in the constellation Ursa Major
Phi Ursae Majoris, Latinized from φ Ursae Majoris, is binary star[11] system in the northern constellation of Ursa Major. It is white-hued and is visible to the naked eye with a combined apparent visual magnitude of +4.60;[2] the primary is magnitude 5.28 while the secondary is magnitude 5.39.[11] The system is located at a distance of approximately 510 light-years (160 parsecs) from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −14.7 km/s.[5] It should make its closest approach at a distance of around 370 light-years in about 4.7 million years.[6]
As of 2017, the components had an angular separation of 0.50″ along a position angle of 304°.[3] They are orbiting each other with a period of 105.4 years and eccentricity of 0.44.[7] Both of components are A-type subgiant stars[12] with a stellar classification of A3 IV.[4]
Phi Ursae Majoris is moving through the galaxy at a speed of 21.6 km/s relative to the Sun. Its projected galactic orbit carries it between 24,000 and 46,000 light-years from the center of the galaxy.[6]