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Pulsars are very interesting astronomical objects. Put simply, a
pulsar is just a neutron star that happens to have a strong magnetic
field and happens to be rapidly rotating. Charged particles near the
neutron star are accelerated along the magnetic field lines, which
produces radiation (light) that is beamed along the magnetic axis. As
the magnetic axis rotates around, the beam of light sweeps across the
sky. If we happen to lie in a direction that intercepts the beam, we
see the pulsar periodically brighten, just like a far-off lighthouse!
So, a pulsar is just a special kind of neutron star, but what's a
neutron star? When a massive star ends its life in a supernova, the
star's core is crushed by incredibly large forces, and it is raised to
extremely high temperatures. This causes all of the atoms in the
star's core to fuse together into one gigantic atom. This atom is
made up almost entirely of neutrons, and it is much denser than
ordinary matter. A typical neutron star weighs more than our Sun, but
it is only 10 km across! (the size of a small city!!)
To learn more about pulsars, neutron stars and supernovae, check
the Ask-an-Astronomer answer archive! Thanks for your question.
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