Scientists now believe that the Milky Way and Andromeda galaxies are expected to collide much sooner than previously anticipated. The cosmic smashup is supposed to take place at about the same time that are sun uses the remainder of its nuclear fuel or in about 7 billion years. According to estimates, our galaxy is moving at 600,000 miles per hour, and we previously thought it was moving at a mere 100,000 mph. Here is a simulation of collision day:

As you can see, after a dramatic collision, the two galaxies will be at separate poles for awhile and then eventually merge into one super galaxy.