Whilst previously, I had called them Geminians, the real term for this alien are Solar Avatars. The aliens are avatars of stars, Trance Gemini is the Solar Avatar of the Tarn-Vedra star, the star that Dylan Hunt's home planet orbits. At the start of the series, Trance Gemini is a purple creature with a tail but she eventually looses her tail and changes.
In later series she has red hair after Trance meets her future self in the episode Ouroboros. There are two Geminians in the series, the main one being Trance Gemini and the later at the end of the final series, we are introduced to Maura who seems to be the leader of the Solar Avatars.
At the beginning of the fifth and final series of Andromeda, we see that Trance Gemini has become a star inside the Andromeda Ascendant but reverts back to her normal form.
Copyright: Tribune Entertainment