The Andromeda Galaxy is the galaxy closest to our own galaxy, the Milky Way. It is about 2.45 million light years away from our solar system. It is located in the constellation Andromeda and can be seen in the northern hemisphere in autumn and early winter. The galaxy was catalogued by Charles Messier in his catalogue with the number 31. 

The Andromeda galaxy has a diameter of about 152,000 light years, making it 1.5 times larger than our own galaxy. Like our own galaxy, Andromeda is a barred spiral galaxy.  Andromeda is expected to collide with the Milky Way in about 4 to 5 billion years.