Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Mu Geminorum is a star in the constellation Gemini, approximately 230 light years away from Earth. It has the traditional name Tejat Posterior, which means back foot, because it is the foot of Castor, one of the Gemini twins. Mu Geminorum is an irregular variable of type LB. Its brightness varies between magnitude +2.75 and +3.02 over a 72 day period, with a 2,000 day period of long term variation. It is a red giant of the spectral class M3, with a surface temperature of 3,650 kelvins, meaning it is brighter, yet cooler than our Sun.