Discovery of pulsars. Abstract photograph depicting the discovery of pulsars by Hewish and Bell in 1967. In the foreground is a negative image of the radio telescope made by Hewish, in the background are modern radio images of known pulsars. The array was built to study the scintillation of quasars, and detected signals at a wavelength of 3.7 metres. Bell was the first to notice unusually regular signals being detected. Hewish and Bell made further measurements, showing the period of the signal to be just over one second, and that it was not man-made. Pulsars are rapidly rotating neutron stars which emit radio beams in a lighthouse-like fashion.