Jocelyn Bell Burnell
(1943- )
Compiled by Peter Ellis

We often dream of making a revolutionary discovery but very few scientists actually do it especially in the first years of their careers, but that is what happened to Jocelyn Bell, the discoverer of pulsars. The young astronomer Jocelyn was born in Belfast, Northern Ireland in 1943. She became interested in astronomy while still very young because her father, an architect, designed Armagh Observatory near where she lived.

Later she went to school in York and then studied science at Glasgow University. After achieving her degree in 1965 she wanted to do research in the relatively new area of radio astronomy.

First build your telescope

Jocelyn wanted to study quasars, groups of stars that are far beyond our galaxy. Quasars give out radio waves, which seem to twinkle as they pass through the dust and gas in the Solar System. She needed a special kind of radio telescope designed by Antony Hewish, her supervisor at Cambridge University, and spent the first two years of her PhD course building it. Radio waves have a much longer wavelength than visible light. To form an image of the radio source the radio telescope must cover an area considerably larger than the wavelength of the radio waves. Jocelyn's radio-telescope consisted of over two thousand separate radio receivers spread over four acres of fields - quite a task to build! At last in July 1967 the telescope was ready and began churning out rolls of paper bearing the ink traces of the radio signals.

Little Green Men?

Almost immediately Jocelyn noticed a strange signal on her rolls of paper. It was a very short burst of radio waves that repeated over and over again at very precise intervals. This was not at all what she had been expecting. Hewish thought it was probably something on Earth interfering with the telescope - a car or a radio transmitter - and he told Jocelyn to check her instruments again and again. Jocelyn couldn't find any faults or a source of interference and over a few weeks was able to see that the source of the strange signal was moving across the sky at the same rate as the stars - in fact it must be as far away as the stars. She measured the signal precisely; it lasted for 0.016 seconds and repeated every 1.337 seconds. This was so unlike any other signal from stars that they joked that it must be little green men, aliens, signalling to other civilisations. Hewish was still not convinced that the signal was real and suggested that Jocelyn look for other similar signals. She searched through the 100m of paper she had collected each week and eventually found three similar repeating signals coming from different parts of the sky. At last Hewish believed that Jocelyn had found something special and he named them "pulsating stars" which soon became shortened to "pulsars".

Missing the Nobel Prize

The discovery of pulsars was announced in 1968 and the media were fascinated. Soon other pulsars were found and astronomers searched for an explanation of their behaviour. Thomas Gold, an American, suggested that pulsars were spinning neutron stars, the remnants of a supernova. In a neutron star the electrons and nuclei of atoms are compressed together forming an extremely dense mass of neutrons. Jocelyn's first pulsar was a neutron star just fifteen kilometres in diameter, and giving off radio waves in a beam as it rotated like a lighthouse lamp. In 1974 Hewish was awarded the Nobel Prize for the discovery of pulsars but Jocelyn didn't get a share. She had completed her doctorate in 1968, married Martin Burnell and had a son. She only worked part time for a number of years, devoting herself to her family. Perhaps the Nobel Prize committee overlooked her because she was not producing scientific papers as regularly as her male colleagues and did not realise the part she had played as a postgraduate student in the discovery.

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