We only have five billion years left until the Milky Way galaxy crashes into Andromeda, our nearest neighbor. What will happen to us then? Because galactic collisions take place over millions or billions of years, the process isn't well understood.
Sometimes galaxies don't just smash into each other — sometimes they just tear each other apart with their gravitational forces. Check out this new Hubble image of NGC 1911 in the Coma Cluster, being torn asunder by neighboring galaxies.
Stephan's Quintet sounds like the name of a nice jazz group, but this galactic cluster, discovered 250 years ago, is actually one galaxy passing through four others at nearly 2 million miles per hour. Hence the long tails. [Chandra Observatory]