Many people wonder what happens when two galaxies collide? The truth is, what could happen when galaxies interact largely depends on the composition and size of the galaxies that are colliding. The best way you can think about galaxies meeting is by thinking of them as “merging” instead of “colliding.” Planets and stars will not run into each other. Galaxies contain a lot of space, and it is more likely that stars will pass by each other. Scientists like to imagine the “collision” as two swarms of bees flying towards each other.
Many large galaxies can attract a smaller galaxy. The gravity of the large galaxy will pull the smaller one towards it, creating a collision. If one galaxy has enough momentum, the galaxy with enough movement or momentum could keep moving away after the collision. However, most galaxies are pulled towards one another and do not continue moving past each other because they do not have enough momentum and the gravitation pulls are too strong to escape.
This means the larger galaxy begins to change the smaller one and merge this small galaxy into the larger one. Galaxies are made up of stars, material, gas, rocks, and dust. When galaxies merge, the gasses interact with each other. Gasses in galaxies exist in large clouds that are spread throughout the galaxy system. This means that large clouds of gasses are more likely to run into other large clouds of gasses. The gasses begin to become dense and experience more pressure. The combination of gasses can cause waves, and the gasses can collapse on themselves: Both of these actions cause new stars to form.
When two galaxies of the same size are merging, many new stars form, making the merging galaxies brighter. However, if these galaxies merge too quickly, many of the newly formed stars are likely to die shortly after their formation. As they begin to approach one another, the galaxies begin to stretch and deform, creating tails or arms. The combination of the two galaxies then forms what appears to be an elliptical galaxy as the arms begin to disappear. The merger of gasses creates new stars, and the new shape becomes more elliptical, globular, or sometimes irregular.
The merger can create a new supergalaxy. Stars from each galaxy will probably move to a new location within this new supergalaxy, meaning the relationship one planet has to other planets and star systems will no longer exist.
Keep in mind that these mergers take a few billion years to complete. They do not happen in the blink of an eye. The Milky Way galaxy and the Andromeda galaxy are moving towards each other on a collision course. It will take millions of years for both to collide. Scientists think that the black holes within the Andromeda and Milky Way galaxy will combine, but they do not know how this will affect the rest of the galaxy.
When you’re wondering what happens when two galaxies collide, try not to think of objects smashing into each other or violent crashes. Instead, as galaxies collide, new stars are formed as gasses combine, both galaxies lose their shape, and the two galaxies create a new supergalaxy that is elliptical.