LETTER: Analysis of the pulsar discovery

From Professor A. Hewish, FRS

Sir: Allow me to correct an untrue statement about the pulsar discovery, ascribed to John Maddox, and quoted by Paul Vallely in his article (News Analysis; "The Nobel art of picking winners", 10 October) on the Nobel awards. He writes "... though Hewish was director of the project, it was a research assistant, Jocelyn Bell, who did the actual work".

The actual work involved a sky survey of scintillating radio galaxies which I conceived and for which I designed and built a new radio telescope especially sensitive to rapid changes of source intensity. Jocelyn ran the survey for her PhD research and reported an unusual source showing strong intensity variations, apparently changing its position by about one degree and sometimes disappearing for several days.

I decided to investigate more closely using a high-speed recorder which Jocelyn operated and recorded the first pulses. I then analysed the pulse phase which gave more accurate positional data and found that the position was actually constant.

I set up and made the timing measurements which showed the incredible precision of the pulses and I exploited this, via the Doppler effect, to confirm that the signals could not be from intelligent beings on a distant planet - a possibility that could not be ignored. I also organised measurements of the radio spectrum which enabled me to estimate the distance of the source.

There was more to the discovery than is often realised from popular accounts of the work.

Yours sincerely,

Antony Hewish

Department of Physics

University of Cambridge

Cambridge

11 October