The Oxford Science Lecture Series

PROFESSOR JOCELYN BELL BURNELL

Professor of Physics, Open University

"Pulsar Puzzles"

University Museum, Oxford, 13th March 1997

The second in the 'Oxford Science Lecture Series' was given on March 13 1997 by Jocelyn Bell Burnell, Professor of Physics at the Open University. 'Pulsars', or 'pulsating stars', were discovered through the detection of rapid `bleeps' in radio signals from previously unsuspected sources, and are arguably the most bizarre class of objects so far known in the cosmos. In order to set the scene and to discuss where astronomers believe pulsars should be placed in the evolving Universe, Jocelyn first took her audience through a Cook's Tour of the better-known realms of the cosmos -- the solar system, nearby stars in space, the Galaxy and other distant galaxies. She then traced briefly the birth and evolution of a star from an almost random aggregation of particles to an incandescent condensation of matter (a 'star') until it finally exhausts its nuclear fuel and explodes as a supernova, leaving at its centre a tiny core of unimaginably dense material. The combination of the pulsar's phenomenal magnetic field with its rapid rotation is thought to be responsible for the 'beam' of radio waves, which sweeps round rather like a lighthouse beam and gives rise to the amazingly regular, rapid pulses.

Jocelyn's initial discovery of these objects has developed into a major field of astronomical research. In fact, most of the findings have presented major challenges to the relevant theoretical concepts, and investigations of their fascinating properties continue to open up more questions than they answer.

The lecture was very enthusiastically received, its clarity enhanced both by the use of modest but highly effective audio-visual aids (such as a bleeping kitchen timer) and also by the speaker's style of unravelling events as they had actually occurred in history and retracing with the audience the path of her discoveries. Thus we also began by hearing (though in our case from a tape-recording) the 'bleeps' from the first known pulsar, considered with her the evidence for something strange and new that could send unprecedentedly regular radio signals, we puzzled with her over their origin - was it a nearby source, or Little Green Men from another world? - and shared her relief when she discovered a second pulsar in a different part of the sky and thereby reduced effectively to zero the chance that alien civilizations were responsible.

Dr Elizabeth Griffin.