Before the Sloan Digital Sky Survey, astronomers knew of 11 dwarf galaxies caught in the gravity of the Milky Way galaxy. But cosmologists believed there should be from 10 to 100 times more dwarf galaxies surrounding large galaxies like the Milky Way. The number of dwarf galaxies is increasing as astronomers continue to scan for more dwarfs.

A large international group of astronomers led by Vasily Belokurov and Daniel Zucker of Cambridge University in England has discovered many more dwarfs galaxies by studying the overdensity of stars in fields and determining or recognizing them as dwarf galaxies. The fields were centered in the constellations of Canes Venatici, Coma Berenices, Hercules, and Leo. The satellite galaxies have been confirmed by ground-based telescopes.

The newly discovered satellite galaxies are thin congregations of only a few million stars each, and are spread over several hundred light-years of space. The result is extremely low surface brightnesses. Their irregular shapes suggest that they are being tidally disrupted by the Milky Way. That means the gravity of the Milky Way is affecting the gravitational fields within the smaller galaxies. The satellite galaxies will change their shapes and motions, and eventually be torn apart and absorbed by the Milky Way.