Here's why:

* Neutron Stars: These are incredibly dense objects formed from the collapsed core of a massive star after a supernova.

* Spinning: Pulsars are born spinning extremely rapidly.

* Pulsating Radio Waves: As a pulsar spins, its powerful magnetic field emits beams of radio waves (and sometimes other types of radiation) that sweep across space. From Earth, we observe these beams as regular pulses of energy, hence the name "pulsar".