1.   If they were only fragments, Kormendy said, their density would have to be lower than that of normal galaxies.

2.   Others look like normal galaxies.

3.   The high-flying astronomers have made several observations of Seyfert galaxies, a type whose cores are spewing out far more energy than normal galaxies.

4.   The most widely accepted model is that a quasar is powered by a supermassive black hole in the core of a more or less normal galaxy.