Andromeda galaxy. Optical image of the Andromeda galaxy (M31, NGC 224). North is at right. This is the closest major galaxy to our own, lying around 2.2 million light years away in the constellation Andromeda. It is the largest galaxy in our local group, around 180,000 light years across. The Milky Way, our own galaxy, is around 120,000 light years across. The Andromeda galaxy has two satellite galaxies associated with it: M32 (bright star-like point above and left of M31's nucleus) and NGC 205 (fainter, below M31's nucleus).