The Expansion of Cassiopeia A

This paper describes a detailed comparison of radio maps of Cas A obtained with the Cambridge 5 km Radio Telescope in 1974 and 1978. Accurate proper motions and brightness changes are presented for 342 distinct radio peaks, ranging in angular size from 1 arc minute for fragments of the intense ring to less than the resolution limit of 2.0 × 2.3 arc seconds for the compact radio knots.