Tau4 Serpentis
Tau Serpentis, Latinized from τ Serpentis, is a M-type bright giant star in the constellation of Serpens, approximately 520 light-years from the Earth. It is classified as a semiregular late-type variable star, and its magnitude varies between +5.89 and +7.07 with a period of approximately 100 days. τ is unique among the stars with the Bayer designation τ Serpentis as being the only one with no HR catalog number.