Did you know that Hubble space telescope has been operating already 18 years? To celebrate this anniversary NASA has published 59 new pictures of colliding galaxies. This is the biggest single set of Hubble pictures ever published.

Collisions of galaxies is just normal evolution, but it all happens in such a long time period and within such a big scale that seeing it happen in a picture is absolutely stunning. A typical collision of galaxies lasts hundreds of millions of years, so it is far from Hollywood movies

A beginning collision can be detected from a material bridge between galaxies which is caused by gravitational forces of the galaxies. The shock waves of collisions form great amounts of new stars that increase the brightness of the galaxies.

Billions of years ago, as the universe was young, collisions of galaxies was more common. Galaxies collided more often due to lack of space in the young and small universe.

Read more about the pictures of colliding galaxies in NASA’s website.

Here is a bigger picture of the gallery.