Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Mu Ursae Majoris is a star in the constellation Ursa Major. Mu Ursae Majoris is a M-type red giant with a mean apparent magnitude of 3.0m. It is approximately 250 light years from the Earth. It is classified as a Semiregular variable star and its brightness varies from magnitude 2.99m to 3.33m. Spectroscopically it has been determined that this is a double star with a companion a mere 1.5 AU from the primary with a rotation period of 230 days.