Gamma-ray astronomy at high energies

Progress in high-energy gamma-ray astronomy has depended upon the developme nt of sophisticated detectors and analysis techniques. Observations in this decade using space-based and ground-based detectors have observed gamma-ra y emission from a variety of sources. For the first time a consistent pictu re of the gamma-ray sky has emerged. This article describes the detection t echniques in gamma-ray astronomy, the nature of the astrophysical objects s tudied, and the present state of the observations. Several possible new dir ections in the field are also described. [S0034-6861(99)00304-9].