The Angular Size of the Variable Radio Source Hydra?A

Abstract

Slee (1955) has shown that the discrete cosmic radio source Hydra-A shows variations in intensity at metre wavelengths. This is the first variable radio source to be found, other than the Sun, although Ryle and Elsmore (1951) investigated about one hundred northerly sources and found no significant variations in their intensities over a period of 18 months. The observations to be described here were undertaken firstly to check the variability of the source, then suspected by Slee, and secondly to measure its angular size and see whether this might also be variable.