Propus (stars.astro.illinois.edu)PROPUS (Eta Geminorum). Gemini, the Twins, represented by Castor (Alpha Geminorum) and Pollux (Beta Gem) at its northern end, is anchored at the bottom by Alhena (Gamma) and at the southwest corner by a pair of similar stars, Tejat (Mu Gem) and our Propus, to which Bayer assigned the Greek letter Eta.