Pollux — Double Star in Gemini

Pollux is the brightest star in the constellation Gemini at magnitude 1.14, slightly outshining its twin Castor. It is an orange giant of spectral type K0III, located only 34 light-years from Earth. Pollux is about 9 times the diameter of the Sun, nearly twice its mass, and about 33 times more luminous. In 2006, a planet was confirmed orbiting Pollux — Pollux b (also called Thestias), a gas giant at least 2.3 times the mass of Jupiter in a 590-day orbit.

Pollux and Castor form the heads of the celestial twins, making one of the most recognizable pairs in the sky. Pollux is slightly brighter and noticeably more orange than the blue-white Castor — this color contrast is delightful through binoculars. While Castor is a spectacular multiple star system, Pollux is a single star. The famous open cluster M35 lies at the feet of Gemini, about 9 degrees to the northwest. Best observed from December through May.

Named after Pollux, the immortal twin from Greek mythology (son of Zeus), while Castor was the mortal twin (son of King Tyndareus). Despite being the brighter star, Bayer designated it Beta Geminorum — possibly because Castor was listed first by Ptolemy or because the 'head' twin traditionally took precedence. The planet Pollux b, confirmed in 2006 by Artie Hatzes and colleagues, was one of the first exoplanets found around a giant star.