 The name Algol means "demon star" (from "al-ghūl"), which was probably given due to its peculiar behavior.Another visible ternary is Alpha Centauri, in the southern constellation of Centaurus, which contains the fourth-brightest star in the night sky, with an apparent visual magnitude of −0.01.This system also underscores the fact that no search for habitable planets is complete if binaries are discounted.