A brief summary of some highlights in the study of high energy astrophysical
sources over the past decade is presented. It is argued that the great progress
that has been made derives largely from the application of new technology to
observation throughout all of the electromagnetic and other spectra and that,
on this basis, the next decade should be even more exciting. However, it is
imperative to observe cosmic sources throughout these spectra in order to
obtain a full understanding of their properties. In addition, it is necessary
to learn the universal laws that govern the macroscopic and the microscopic
behavior of cosmic plasma over a great range of physical conditions by
combining observations of different classes of source. These two injunctions
are illustrated by discussions of cosmology, hot gas, supernova remnants and
explosions, neutron stars, black holes and ultrarelativistic outflows. New
interpreations of the acceleration of Galactic cosmic rays, the cooling of hot
gas in rich clusters and the nature of ultrarelativistic outflows are outlined.
The new frontiers of VHE γ-ray astronomy, low frequency radio astronomy,
neutrino astronomy, UHE cosmic ray physics and gravitational wave astronomy are
especially promising.Comment: To appear in "High Energy Processes and Phenomena in Astrophysics,
IAU Symposium 214", X. Li, Z. Wang, V. Trimble (eds
