Radio-Frequency Radiation from the Constellation of Cygnus

Abstract

Observations are described of the radiation from portion of the constellation of Cygnus at frequencies of 1210 and 3000 Mc/s. Two sources of radiation were observed at the lower frequency, one being the well-known "radio star ", Cygnus-A. The other was a diffuse source of limited extent which might be called a " radio nebula ". Neither source could be observed at the higher frequency. The properties of both sources, particularly their spectra, are discussed and it is shown that earlier discrepancies in observations of the Cygnus region may be explained. The diffuse source coincides in position with the secondary maximum in the lower frequency galactic contours, which Bolton and Westfold (1950a, 1950b) have interpreted as a spiral arm of the Galaxy. The new evidence suggests that the source is probably due to thermal emission from clouds of ionized interstellar gas, possibly in the region of γ Cygni and having a temperature and electron density of the order of 10⁴ °K, and 10 cm^-3 respectively.