Tau Puppis

Tau Puppis (Tau Pup, τ Puppis, τ Pup) is a star in the southern constellation of Puppis. It has an apparent visual magnitude of +2.95 and is located at a distance of about 182 light-years (56 parsecs) from Earth. This is a spectroscopic binary star system, with the presence of the secondary component being revealed by the shifts of absorption lines in the spectrum resulting from the Doppler effect. The two components orbit each other with a period of 1,066.0 days (2.9 years) and a low eccentricity of 0.090.

The primary component of this system has a stellar classification of K1 III. A luminosity class 'III' indicates this has expanded into a giant star after exhausting the supply of hydrogen at its core and evolving away from the main sequence of stars like the Sun. The interferometry-measured angular diameter of this star, after correcting for limb darkening, is 4.49 ± 0.07 mas, which, at its estimated distance, equates to a physical radius of about 27 times the radius of the Sun. It appears to be rotating slowly, with a projected rotational velocity of 2.2 km s⁻¹. This gives a lower bound on the azimuthal velocity of rotation along the star's equator. Tau Puppis is radiating energy from its outer envelope at an effective temperature of around 4,500, giving it the orange hue of a cool, K-type star.