reddish giant star in the constellation Taurus. Aldebaran is one of the 15 brightest stars, with an apparent visual magnitude of 0.86. Its diameter is approximately 50 times that of the Sun. It is accompanied by a very faint (13th magnitude) red companion star. Aldebaran lies about 65 light-years from the Earth. The star was once thought to be a member of the Hyades cluster, but in fact Aldebaran is 85 light-years closer to Earth. Aldebaran was probably named “The Follower” because it rises after the Pleiades cluster of stars.