The Andromeda Galaxy is a barred spiral galaxy and is the nearest major galaxy to the Milky Way. It was originally named the Andromeda Nebula and is cataloged as Messier 31, M31. Andromeda has a diameter of about 152,000 light-years, or 1.438 x 10^18 km and is approximately 2.5 million light-years, or 2.36518262 x 10^19 km from Earth. The galaxy’s name stems from the area of Earth’s sky in which it appears, the constellation of Andromeda, which itself is named after the princess who was the wife of Perseus in Greek mythology.
The Andromeda galaxy is very large in the night sky by deep space standards. The Milky Way galaxy, in which the Earth is part, and Andromeda galaxy are expected to collide with each other in around 4–5 billion years.
This image is a mosaic comprised of 7 panels, taken in a single evening in Crestone, Colorado, designated a Dark Sky community.