The first pulsar (CP 1919, PSR B1919+21)

Parts from the Cambridge Interplanetary Scintillation Array, 1967

This is part of the four-acre radio telescope used in one of astronomy’s most famous chance discoveries. In 1967, student Jocelyn Bell noticed a ‘bit of scruff’ on the telescope’s data charts. Astronomers realised that the unusual signal, which repeated regularly, came from a new class of cosmic object. Initially, these objects were nicknamed LGM, for ‘little green men’. But rather than aliens, they are rapidly spinning dense stars. They are called pulsars and over 1800 are now known.
Model of a pulsar, c. 1969

Antony Hewish used this model to teach people about pulsars – the new kind of star he and Jocelyn Bell discovered in 1967. The orange ball at the centre represents a neutron star, the incredibly dense remnant of a supernova explosion. The curved wires show magnetic field lines. The foil tubes represent beams of radiation from the neutron star. As the star rotates, the beam turns in the direction of the Earth, and astronomers detect radio pulses. Hewish’s first version of the model was driven by a gramophone motor.