Physics Colloquium 5th May 2017 delivered by Dame Professor Jocelyn Bell Burnell Pulsars, or pulsating radio stars, were discovered accidentally 50 years ago. Dame Professor Bell Burnell will give a brief account of the equipment used and the discovery. We now understand pulsars to be rapidly rotating neutron stars (1ms P 10s, R ≈ 10km, surface speed 10%c) which manifest extreme physics in several dimensions (average density = nuclear, surface B up to 1011T). Dame Professor Bell Burnell will describe the main features of pulsars and indicate how they are impacting our understanding of physics today.