Spinning Neutron Star
Radio waves from the star sweep across the sky. An observer on Earth will see a short radio pulse when the beam sweeps in our direction.

6. Explaining the Pulse

A few days before the paper was published, Hewish announced the results at a meeting of Cambridge astronomers. On hearing the results Professor Fred Hoyle suggested that the pulsar could be the remains of a supernova. In the published paper it was suggested that the pulses could be due to pulsed emissions from theoretical neutron stars, remnants of stars left after a supernova explosion.

Three months later Thomas Gold at Cornell University in Ithaca, USA, published a more satisfying explanation for the pulsed signals. Gold suggested that the radio signals were coming from neutron stars, but that the neutron stars were rotating, spinning around an axis. The neutron star wouldn't need to be emitting pulses of radiation, but could emit a steady radio signal that it swept around in circles like light from a lighthouse. When the pulsar 'lighthouse' was pointing at Earth we could detect the signal, which would show up as the short pulse that Bell had observed.

But these pulses were observed nearly once a second! Could a star really spin this fast? Gold explained that a neutron star could, and that most pulsars should be spinning even faster than the first two observed by Jocelyn Bell. This was because of the way in which neutron stars form.

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