Andromeda, in astronomy, northern constellation located to the NE of Pegasus and to the S of Cassiopeia. Its brightest star, Alpheratz (Alpha Andromedae), marks the northeast corner of the Great Square in Pegasus. The constellation also contains the bright stars Mirach (Beta Andromedae) and Almach (Gamma Andromedae) and the famous Great Nebula, or Andromeda Galaxy, the only galaxy visible to the naked eye in the Northern Hemisphere. Andromeda reaches its highest point in the evening sky in November.
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