Pulsar.

Pulsar Pulsars are highly magnetized, rotating neutron stars that emit a beam of electromagnetic radiation. The observed periods of their pulses range from 1.4 milliseconds to 8.5 seconds. The radiation can only be observed when the beam of emission is pointing towards Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name. Because neutron stars are very dense objects, the rotation period and thus the interval between observed pulses are very regular. Pulsars are known to have planets orbiting them. The theory of how pulsars emit their radiation is still unknown even after forty years of work.