Cosmic collisions occur when galaxies are very close to each other and their mutual gravitational forces pull them together. Although these interactions take place over millions and millions of years, the Hubble Space Telescope has helped us observe these galaxy mergers in progress.

The interacting galaxies, UGC 3912, LEDA 60847, Arp 295 and Arp 140, respectively, show signs that they are merging with a neighbouring galaxy or are after a merger when you scroll through the images. Other signs of these mergers are the emergence of multiple nuclei from different galaxies coming together, or even "tail" structures emerging from the galaxy itself as a result of galaxies gravitationally interacting with each other.

Image description: A collection of images showing colliding galaxies as seen by the Hubble Space Telescope. Some galaxies have moved away from their original shapes and appear to be clouds of gas and dust. Spiral arms have separated from spiral galaxies and some galaxies have become a cosmic pennant. Galaxies are dominated by shades of blue, pink and white. Smaller galaxies and stars are seen in the background with the darkness of space.