Chi Geminorum
Star in the constellation of Gemini
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Chi Geminorum (χ Gem) is a binary star system in the constellation Gemini, near the eastern border with Cancer. It can be viewed with the naked eye on a dark night, having an apparent visual magnitude of 4.98.[3] Based upon an annual parallax shift of 12.73 mas,[2] it is located roughly 260 light years from the Sun.
The two components of this system form a spectroscopic binary with an orbital period of 2,437.8 days and an eccentricity of 0.06.[8] The primary component is a K-type giant star with a stellar classification of K2 III.[5] This is a candidate mild Barium star with the slight overabundance most likely acquired through accretion from what is now a white dwarf companion.[10] The primary has an estimated 1.83[5] times the mass of the Sun and has expanded to 14 times the Sun's radius.[6] The effective temperature of the outer atmosphere is 4,560 K, from whence it radiates 79 times the solar luminosity.[6] It has a leisurely projected rotational velocity of 3.8 km/s[6] and is around two billion years old.[5]