Gemini constellation. Stars of Castor (at centre) and Pollux (at lower centre) in the constellation of Gemini (the Twins). Castor (Alpha Geminorum) & Pollux (Beta Geminorum) form the heads of 2 twins; the bodies are represented by dimmer stars towards bottom left. The stars often represented opposing characters or behaviours in mythology. Castor is not a single star but a system of 3 binary stars about 45 light years away. The components of these stars orbit around each other every 2.9 days, 9.2 days and 10,000 years respectively. Pollux is a single star about 35 light years away which, although cooler than the Sun, has four times the diamater and is 35 times as bright.