“There are something like a trillion galaxies in the observable universe, of a range of sizes. And galaxy collisions happen a lot.

In fact, galaxies primarily grow by cannibalizing other (smaller) galaxies. Our own has eaten several—we can see streams of stars as debris.

In fact, galaxies primarily grow by cannibalizing other (smaller) galaxies. Our own has eaten several—we can see streams of stars as debris.

In addition to making the galaxies look like a train wreck (this is the term we often use), the merging can also cause new stars to form.

Throwing a lot of gas together & stirring it around can create new stars. And it can feed the big black holes too.

For all that chaos, collisions between stars themselves are actually pretty unlikely. There's a LOT of space between stars, even in galaxies.”