The Great Andromeda Galaxy, M31
The Andromeda Galaxy is a spiral galaxy and it the closest large galaxy to the milky way (this is not including dwarf galaxies). It is approximately 2.5 million light-years away in the constellation Andromeda and is listed as the 31st object in Messier’s catalog of large night-sky objects.
Andromeda is one of the easiest objects to spot in the night sky. It can be seen on a clear night with the unaided eye as a faint smudge of light about 3 times the apparent length of the moon. This makes the Galaxy a great viewing/imaging target if you have a pair of binoculars or a telescope.
Like our milky way galaxy, the Andromeda galaxy has smaller satellite galaxy, known as dwarf galaxies, that orbit it. One of these dwarf galaxies can be seen in the above images as a small smudge below Andromeda’s galactic disk.
The top image shows a wide field view of the Andromeda Galaxy. The next two images show wide field views of the galaxy in infrared and ultraviolet light and the last two are infrared and ultraviolet images taken recently by the Spitzer space telescope.