This is not some casual animation. It is based on well established laws of physics, rigorous math, and a lot of computer power. About 3 billion years is compressed into a couple minutes, which may be a time-lapse record.

A galaxy like ours has roughly 100 billion (10¹¹) stars. This is a very large scale event. It would be the end of the world, for billions of worlds. It is about as large a catastrophe as the universe can dish out.

It is also lovely.

Yes. It really does happen. Astronomers have photographed colliding galaxies. It is a violent universe out there.

More at Bad Astronomy.