A "pulsar" is a type of neutron star that appears to "blink" periodically when observed with radio telescopes. This type of neutron star has a strong magnetic field that concentrates electromagnetic radiation into a narrow beam shooting from the magnetic poles. This magnetic field is misaligned with the axis of rotation, so the beam sweeps through space as the star spins. An observer will only receive this beam from times where the beam is pointed towards them, appearing as pulses in the signal.