The Nuclei of Normal Galaxies: Lessons from the Galactic Center

Our Galactic center's proximity allows astronomers to study physical pro­ cesses within galactic nuclei at a level of detail that will never be possible in the more distant, but usually also more spectacular, extragalactic systems. Recent advances in instrumentation from the radio, through the submillime­ ter and infrared wavebands, and out to the X- and "'(-ray bands now allow observations of the Galactic Center over thirteen orders of magnitude in wave­ length. Our knowledge about the central few hundred parsecs of our Galaxy has consequently increased vastly over the past decade. The same new instru­ ments provide high resolution, high quality measurements of nearby ''normal'' galactic nuclei; that is, nuclei whose modest energy output is comparable to that of our own (and most other) galaxies. Theorists, spurred in part by the new observations, have been able to refine models of the energetics, dynam­ ics, and evolution of the gas and stellar systems deep within galactic nuclei.