As vast and empty as the universe appears to be, astronomers believe it is possible for galaxies to collide. Indeed, it is not uncommon for them to move directly through one another. When this happens, their stars mix and the galaxies become distorted. Sometimes they merge entirely, although over so long a period of time that they will not appear noticeably different during the entire course of human history.
The galaxy 3C 75ΓÇöseen here in a false color imageΓÇömay be such an object. A large galaxy extending across 150,000 light years, 3C 75 lies at the center of the distant cluster Abell 400. Most galaxies have only one nucleus, or central concentration of stars. 3C 75ΓÇÖs most striking feature is that it has two. The double nucleus may indicate
