Physics of nonthermal radio sources

The fundamental observational problem in radio‐astronomical investigations of discrete sources is the determination of the precise positions and spectra of these objects, as well as measurement of the brightness distributions of those sources large enough to be resolved by existing equipment. Recently, polarimeter measurements at a number of frequencies have provided data on the percentage of linear polarization and position angle of the electric vector for some of the more intense sources. This work, in turn, has made it possible to study the effects of Faraday rotation on the cosmic radio waves, leading to model‐dependent estimates of the electron density and magnetic field strength in interstellar and intergalactic space.