Astronomers have spotted the eroding remains of 100 dwarf galaxies that have been violently stripped of their outer layer of stars by larger galaxies. These disrupted galaxies represent the "missing link" in the evolution of a puzzling type of galaxy called ultra-compact dwarf galaxies (UCDs).
The discovery shows that UCDs — which are among the densest collections of stars in the universe — are the fossilized remains of normal dwarf galaxies that have been destroyed in violent gravitational encounters with other galaxies.
Astronomers first discovered UCDs more than two decades ago. The ultra-dense galaxies posed a mystery for astronomers because they are smaller and more compact than ordinary dwarf galaxies but larger than the star clusters they most closely resemble. Scientists theorized that UCDs were the remains of destroyed dwarf galaxies, but they lacked an intermediate galaxy to help confirm the transition.
