Fifteen Months of Pulsar Astronomy

Abstract

Towards the end of February 1968 the astronomical world was staggered by a paper from the Milliard Radio Observatory at Cambridge announcing the discovery of an astonishing periodic phenomenon. The characteristics of the pulsating radio source—or pulsar as it came to be called—involved a fantastic multiplicity of time-scales. The duration of the individual events was measured in tens of milliseconds, the repetition rate was of the order of a second, the pulse amplitude showed drastic variations over times of seconds, minutes, hours and even months and, lastly, the stability of the basic periodicity indicated a time-scale of millions of years. A series of pulses from CP 1919, the first pulsar, is shown in Figure 1, and one notices here both the regularity of the pulses and the variation in their amplitude with time. When the individual pulses were observed on an expanded time-scale it was found that the pulses were made up of sub-pulses (Figure 2) and that there was considerable structure even down to a millisecond time-scale.