Chi

Its story

Chi Geminorum is an orange K2 giant whose surface burns at only 4,540 K, a thousand degrees cooler than the Sun. At 256 light-years it is also a spectroscopic binary: a companion invisible to telescopes betrays itself only through the swaying spectral lines of the primary. It shines in the Twins, the zodiac constellation where Castor and Pollux mark the two ends of the old Greek myth of brotherhood.