Many, if not all, dead 'neutron stars' are probably pulsars, but we can only see the effect if the beams of radiation they send out are lined up directly with Earth.
Pulsars are 'neutron stars', which form in the aftermath of a supernova explosion.
When a giant star comes to the end of its life, and stops burning fuel, its outer layers are blown off in an enormous explosion, and its core then collapses to a ball only a few kilometres across. The neutron star can reach speeds of hundreds of revolutions each second - only the enormous gravitational pull caused by its mass stops it flying apart. In the same way as the angular momentum of the star is conserved as it collapses, so is its magnetic field. The same amount of magnetic force suddenly has to pass through a much smaller surface, so the field lines are condensed and magnified, creating an enormous magnetic field, which channels radiation from the star out at only two points, the magnetic North and South poles. The radio waves are caused by an effect called synchrotron radiation' - particles give off energy as they become trapped in the strong magnetic field.