Small galaxies have fewer than a billion. Astronomers have photographed millions of galaxies through telescopes. They estimate that there are about 100 billion galaxies in the universe. Galaxies are distributed unevenly in space. Some galaxies are found alone in space, but most are grouped in formations called clusters.
Clusters of galaxies range in size from a few dozen members to several thousand.
There are three types of galaxies. These types are called spiral galaxies, elliptical galaxies, and irregular galaxies. A spiral galaxy is shaped like a disk with a bulge in the center. The disk resembles a pinwheel, with bright spiral arms that coil out from the central bulge. The Milky Way is a spiral galaxy.