The Great Andromeda Galaxy or M31 is a spiral galaxy approximately 2.5 million light-years from Earth in the Andromeda constellation.
It is the nearest spiral galaxy to our Milky Way galaxy, but not the nearest galaxy overall.
It is gravitationally bound to the Milky way and the two galaxies are expected to collide in 3.75 billion years, eventually merging to form a giant elliptical galaxy.
However the stars in the galaxy are so far apart that the merge is unlikely to cause any stars to collide with each other.
For instance our nearest star, alpha centuary, is 25 trillion miles away.
The Andromeda Galaxy contains roughly one trillion stars, while the Milky Way Galaxy is estimated to contain roughly 100 billion stars.
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