Galaxy collisions are a slow-speed, spectacular crash of whirling stars driven by gravity. A new simulation from NASA's Goddard Space Flight Center runs through the history of the universe in under a minute, with galaxies swirling together in a beautiful mess of dust and stars.
From the video description:
Galaxies are collections of stars, gas, dust and dark matter held together by gravity. Their appearance and composition are shaped over billions of years by interactions with groups of stars and other galaxies. Using supercomputers, scientists can look back in time and simulate how a galaxy may have formed in the early universe and grown into what we see today. Galaxies are thought to begin as small clouds of stars and dust swirling through space. As other clouds get close, gravity sends these objects careening into one another and knits them into larger spinning packs. Subsequent collisions can sling material toward a galaxy's outskirts, creating extensive spiral arms filled with colonies of stars.
Collision of spiral galaxies NGC 2207 and IC 216. Image credit: NASA/Hubble Space Telescope
Galactic collisions are in the skies all around us. The astrophotography of these catastrophic events are beautiful, with stars and dust flung in all directions.
Stephan's Quintet. Image credit: ESA/NASA