Many galaxies are members of groups or clusters. Since groups and clusters contain so lots of galaxies comparatively close together, it ought to not be surprising that galaxies sometimes collide with each other. In fact, the Milky Way Galaxy is colliding with the Sagittarius Dwarf Galaxy right now (see the SDSS First Discoveries for more information). Although galaxy collisions are common, stars in each galaxy are so far apart that collisions between stars are rare.
Even if galaxies don't actually collide, though, they can still affect another. When galaxies pass close to another, the force of gravity they exert on another may cause both galaxies to bend out of shape. Both crashes and near misses between galaxies are often called "interactions."When galaxies interact, clouds of gas inside each galaxy may become compressed. Compressing the clouds may cause them to collapse under their own gravity, turning in to stars. This process can lead to a burst of star formation in interacting galaxies, leaving a new generation of stars in a galaxy where normal star formation may have ceased long ago.
At the right, you can see galaxies interacting. You can see they are being distorted by the gravitational interaction between them. Are you able to imagine what they might have looked like before they interacted?
Galaxy collisions take hundreds of millions of years, so they cannot watch them happen. In lieu, they use computer simulations to show us what would happen if galaxies collided in a sure way. In case you are interested in learning about galaxy collisions, you can use a web-based simulation tool to model them.
Even if galaxies don't actually collide, though, they can still affect another. When galaxies pass close to another, the force of gravity they exert on another may cause both galaxies to bend out of shape. Both crashes and near misses between galaxies are often called "interactions."When galaxies interact, clouds of gas inside each galaxy may become compressed. Compressing the clouds may cause them to collapse under their own gravity, turning in to stars. This process can lead to a burst of star formation in interacting galaxies, leaving a new generation of stars in a galaxy where normal star formation may have ceased long ago.
At the right, you can see galaxies interacting. You can see they are being distorted by the gravitational interaction between them. Are you able to imagine what they might have looked like before they interacted?
Galaxy collisions take hundreds of millions of years, so they cannot watch them happen. In lieu, they use computer simulations to show us what would happen if galaxies collided in a sure way. In case you are interested in learning about galaxy collisions, you can use a web-based simulation tool to model them.