Answer: Such galaxies probably formed when two or more spirals, like the Milky Way, merged to form a single galaxy. One bit of evidence supporting the merger theory is a large number of ellipticals in dense clusters of galaxies, where mergers must be common. Two giant ellipticals dominate the center of the densely packed Coma Cluster
Galaxies are thought to begin as small clouds of stars and dust swirling through space. As other clouds get close, gravity sends these objects careening into one another and knits them into larger spinning packs.
