Andromeda is the closest spiral galaxy to our own and lies at about 2.5 million light-years away.
Andromeda is estimated to have a mass of approximately 1.2 million million solar masses and a diameter of 220,000 light-years.
Andromeda is moving towards our galaxy at a speed of about 100 to 140 kilometres per second (400 light-years every million years). This means it is possible that it will collide with our galaxy in about 4.5 billion years. It is not certain that this will happen. If it did, the two galaxies would probably form a large elliptical galaxy. If they didn't merge, the effect on our Solar System is uncertain. It is possible that the Solar System could be ejected from the Milky Way or join Andromeda.
Andromeda is one of the furthest objects that is visible with a naked eye. It can be found quite easily on a clear night. It appears a fuzzy patch and lies somewhere between the constellation of Cassiopia and the constellation Pegassus. Just look below the W or above the M of the Cassiopia as a starting point.