Astronomers don't know for sure if we're in store for a head-on collision or a mere sideswipe. Future telescopes will make precise enough observations to tell for sure, but supercomputer simulations show the collision will cause the Milky Way and Andromeda galaxy to merge together into a single, giant elliptical galaxy.

The Andromeda galaxy will likely first swing by our galaxy and then take perhaps 100 million years to make a slow U-turn before plunging into the Milky Way's core.

Hubble Space Telescope views of spectacular collisions between other pairs of spiral galaxies in the universe have already given astronomers a preview of what's in store for the Milky Way.

The nighttime ribbon and stars and dust that marked the lanes of our Milky Way will begin to come apart under the gravitational tug-of-war between the two galaxies.

The sky will grow increasingly jumbled with shreds of black dust, glowing gas, and "superclusters" of brilliant blue stars. Cold, black molecular clouds will be compressed and heated until they burst apart in a firestorm of starbirth. Supernova explosions from the most massive of the newborn stars will pepper the heavens with titanic blasts going off like a string of firecrackers.

As the stars gravitationally settle into their new home, any hint of the Milky Way and Andromeda as majestic spiral galaxies will be gone. Far-future alien skywatchers will gaze into a rich starry sky and look all the way across space into the brilliant core of our newly formed elliptical galaxy.