Castor (star)
Castor is the second brightest object in the zodiac constellation of Gemini. It has the Bayer designation α Geminorum, which is Latinised to Alpha Geminorum and shortened to Alpha Gem or α Gem. It has an apparent visual magnitude of 1.93, which makes it one of the brightest stars in the night sky. Castor appears as a single star to the naked eye, but it is actually a sextuple star system (six stars) organized into three binary pairs of stars designated Castor A, Castor B and Castor C, each containing two stars. Even though it is the 'α' (alpha) member of the constellation, it is fainter than 'β' (beta) Geminorum, Pollux.