Castor is the new name for the Outdoor unit. Castor is the second brightest star in the constellation Gemini and one of the brightest stars in the night-time sky. Although it has the Bayer designation “alpha”, it is actually fainter than Beta Geminorum (Pollux). Castor and Pollux are the two “heavenly twin” stars that give the constellation Gemini (meaning “twins” in Latin) its name. Actually the name Castor refers specifically to Castor, one of the twin sons of Zeus and Leda.