The Andromeda Galaxy is a large galaxy closest to the Milky Way. It is also known as Messier 31, M 31 or NGC 224. It is one of the few galaxies that can be seen from the Earth. In 4.5 billion years, the Andromeda Galaxy and the Milky Way are expected to collide. Since it is the nearest spiral galaxy, astronomers use the Andromeda Galaxy to understand the origin and evolution of galaxies. The Andromeda Galaxy is the most distant object you can spot with the naked eye.