27.5: Key Terms
- active galactic nuclei (AGN)
- galaxies that are almost as luminous as quasars and share many of their properties, although to a less spectacular degree; abnormal amounts of energy are produced in their centers
- active galaxies
- galaxies that house active galactic nuclei
- quasar
- an object of very high redshift that looks like a star but is extragalactic and highly luminous; also called a quasi-stellar object, or QSO