Most galaxies are relatively isolated, with only a few nearby neighbors. However, in some places, hundreds to thousands of galaxies swarm together in a cluster of galaxies. These galaxies all orbit one another, held together by the gravitational forces between galaxies.
At the center of a cluster of galaxies is often a giant elliptical galaxy or even a larger galaxy that is called a central dominant. Giant elliptical and central dominant galaxies seem to have grown bigger by swallowing other galaxies. Some have two nuclei, indicating that they are still digesting their latest meal! Here’s a look at some galaxy clusters.
