Tau4 Eridani
Tau4 Eridani is a binary star system in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude that varies from 3.57 to 3.72. The distance to this star can be estimated using the parallax method, which yields a value of roughly 300 light years.
The primary components ia an evolved red giant star currently on the asymptotic giant branch with a stellar classification of M3/4 III. It is a slow irregular variable star of type Lb, undergoing changes in magnitude over the range 3.57−3.72 with a periodicity of 23.8 d. This star has 1.73 times the mass of the Sun and 103 times the radius of the Sun. It shines with 1,537 times the luminosity of the Sun from its photosphere at an effective temperature of 3,650 K.
The secondary is a magnitude 9.5 star at an angular separation of 5.7″ along a position angle of 291°, as of 2013. This angular separation implies a projected separation of 5,800 astronomical units.