- Gamma Geminorum (γ Geminorum, abbreviated Gamma Gem, γ Gem), formally named Alhena /ælˈhiːnə/, is the third-brightest object in the constellation of Gemini. It has an apparent visual magnitude of 1.9, making it easily visible to the naked eye even in urban regions. Based upon parallax measurements with the Hipparcos satellite, it is located at a distance of roughly 109 light-years (33 parsecs) from the Sun.