They have no business being there. There's no other way to make them, other than to collide stars.

They are the most violent energetic events in the universe. Some release a thousand times as much energy in a few seconds as the sun would in its lifetime.

It you waited ten million times the age of the universe, only then would you have a 50-50 chance of a collision.

Suddenly we're starting to get lots of collisions. There's probably one about every ten seconds.

Most people a few years ago though that collisions didn't happen.