Quasars: The Observational Perspectives

Abstract

The empirical basis of quasar astronomy can be overawing especially in the twenty-first century. A first source of intricacy involves thenomenclature that has evolved to label the multifold phenomenologicalmanifestations now united under the umbrella of active galactic nuclei(AGNs). A further complication involves observations of the manysubclasses with the observations now spanning the electromagneticspectrum.