Here's why:

* Pulsar: A pulsar is a rapidly rotating neutron star. Neutron stars are formed when a massive star collapses at the end of its life, and its core is compressed into a incredibly dense sphere of neutrons. Pulsars emit beams of radiation that sweep across space, and we detect them as pulses.

* White Dwarf: A white dwarf is the remnant core of a low-mass star after it has shed its outer layers. It's primarily composed of carbon and oxygen, and it is significantly less dense than a neutron star.

Key Differences:

* Density: Neutron stars are much denser than white dwarfs.

* Composition: Neutron stars are mostly neutrons, while white dwarfs are mostly carbon and oxygen.

* Formation: Pulsars form from the collapse of massive stars, while white dwarfs form from low-mass stars.

* Rotation: Pulsars are rapidly rotating, while white dwarfs typically rotate much slower.

While both pulsars and white dwarfs are end-stage stellar remnants, they represent different evolutionary paths and have very distinct properties.