The ‘cosmic lighthouses’ known as pulsars were found by accident while a University of Cambridge team were looking for twinkling sources of radio radiation. In 1967 student Jocelyn Bell (born 1943) was using the university’s four-acre array telescope, designed by her supervisor Tony Hewish (born 1924), and noticed a regular pulse in her data.
At first the pulses seemed too regular to be anything other than human in origin - a satellite off course, for example. Having double-checked their results, Bell and Hewish realised that the unusual signal was coming from outer space and was a new class of cosmic object.
Initially these objects were nicknamed LGM for ‘little green men’. But rather than aliens it was soon realised that these signals or ‘pulsars’ were actually radio beams from rapidly spinning, very dense dead stars called neutron stars. Astronomers have since detected more than 1800 pulsars.