The Andromeda Galaxy, located some 2.5 million light-years from Earth, burns brightly in ultraviolet light in this image taken by NASA’s Galaxy Evolution Explorer. (Credit: NASA/JPL-Caltech)

The Milky Way and Andromeda galaxies are the big fish in our corner of the universe, surrounded by dozens of smaller dwarf galaxies. Together, this cosmic community makes up what scientists call the “Local Group.”

Astronomers believe that the largest galaxies grow by attracting and consuming these sm