Andromeda is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and remains one of the 88 modern constellations. Located north of the celestial equator, it is named for the princess in the Greek legend, who was chained to a rock to be eaten by the sea monster Cetus. Its brightest star, Alpha Andromedae, is a binary star, as is bright Gamma Andromedae, a colorful binary and a popular target for amateur astronomers. The constellation's most obvious deep-sky object is the naked-eye Andromeda Galaxy (M31, also called the Great Galaxy of Andromeda), the closest galaxy to the Milky Way and one of the brightest Messier objects. In Chinese astronomy, the stars that make up Andromeda were members of four different constellations that had astrological and mythological signifi