Galactic Radiation at Radio Frequencies. II. The Discrete Sources

An account is given of observations on a number of discrete sources of radio- frequency radiation, together with a brief description of the observational techniques used in their detection, and of the methods employed to determine their positions and angular extent.Noise spectra of four of the more intense sources have been measured over a frequency range of 40-160 Mc/s. : in three cases the change of intensity with wave- length is found to be greater than that of the background continuum, and in one case less. Two of the sources have been provisionally identified with astronomically rare objects, the Crab Nebula and N.G.C. 5128.Finally, the short period fluctuations in the intensity of some of the sources, notably that in Cygnus, are discussed. Evidence is presented which, contrary to previous views, suggests that these fluctuations are of terrestrial rather than of extra-terrestrial origin.