Animation of Milky Way and Andromeda 'galaxy pile-up'
1 June 2012 Last updated at 14:02 BST
Astronomers have used the Hubble Space Telescope to work out when precisely our Milky Way Galaxy will crash into its neighbour, Andromeda.
Computer simulations based on Hubble's data indicate the two great masses of stars will eventually shape themselves into a single elliptical galaxy similar to the kind commonly seen in the local Universe.
This Nasa simulation shows the galaxy merger which scientists say will begin to occur in about four billion years' time.