Alpha Ursae Majoris (Alpha UMa, α Ursae Majoris, α UMa) is the second-brightest star in the constellation of Ursa Major (despite its Bayer designation of "alpha"). It has the traditional name Dubhe, and a rarer name Ak.
This star forms part of the Big Dipper (also known as the Plough or the Great Bear), and is the northern of the 'pointers' (or 'guards'), the two stars of Ursa Major which point towards Polaris, the North Star. Dubhe is about 123 light years away and is a giant star that has evolved away from the main sequence after consuming the hydrogen at its core. It is a spectroscopic binary with a main sequence companion α UMa B that has a stellar classification of F0V. This star orbiting at a mean separation of about 23 astronomical units (AU) and completes an orbit every 44.4 years. More than 90,000 AU distant from this pair is a second binary system that includes an F-type star, making this a four star system.
Although it is part of the constellation of Ursa Major, it does not form part of the Ursa Major Moving Group of stars that have a common motion through space..
Read more about Alpha Ursae Majoris: Name and Etymology, In Culture
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