Tau Ursae Majoris

Tau Ursae Majoris (τ UMa) is the Bayer designation for a binary star in the northern circumpolar constellation of Ursa Major. It is visible to the naked eye, having an apparent visual magnitude of 4.66. With an annual parallax shift of 25.82 mas, it is located about 126 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.19 due to interstellar dust.

This is a single-lined spectroscopic binary star system with an orbital period of 2.9 years and an eccentricity of 0.48. The primary member, component A, is an evolved bright giant with a stellar classification of kA5hF0mF5 II. This notation indicates the star's spectrum shows the K line of an A5 star, the hydrogen lines of an F0 star, and the metallic lines of an F5 star. It is an evolved Am star of the Rho Puppis type and is located in the instability strip of the Hertzsprung–Russell diagram.

With φ, h, υ, θ, e, and f, it composed the Arabic asterism Sarīr Banāt al-Na'sh, the Throne of the daughters of Na'sh, and al-Haud, the Pond.