A Bird's Eye View of a Galaxy Collision

1. What happens when galaxies collide?

When galaxies collide, the stars that are part of each galaxy will almost never collide. They usually pass freely between each other with little damage. That's because the stars are far apart from each other.

But the vast clouds of gas and dust between the stars do smash into each other. These collisions compress the clouds and trigger new star birth. The hot blue stars in this image are evidence of this star formation.