When galaxies collide, the outcome is hard to predict.

The three galaxies have been colliding for hundreds of millions of years.

Astronomers know that in cosmos, galaxies sometimes collide.

When two galaxies collide, the material is pulled out in strands, allowing astronomers to determine which way the galaxies are moving.

This occurs when two galaxies collide and do not have enough momentum to continue traveling after the collision.

These mergers can be extremely violent; galaxies often collide at speeds of 500 kilometers per second.

Most quasars were active in the early universe, which was smaller, so galaxies collided more frequently.

When two galaxies collide, they actually pass through each other.

When two galaxies collide, one galaxy may be stripped of its gas and dust.

Our galaxy will probably collide with the Andromeda galaxy in about 3bn years.