Electrons are degenerate. Mass of Sun compressed to size of Earth. Neutrons and protons have room to move around freely. White dwarf cools off from initial formation temperature of about 100,000 K. Form as outer layers of red giant star puff out to make planetary nebula. Compression so great that protons fuse with electrons to form neutrons.
Neutrons are degenerate.
Formed in supernova explosion. Light flashes with period of milliseconds at start and lengthening to periods of about 4 minutes over time. Slowly rotating Red Giant star has same angular momentum as tiny, fast rotating neutron star. Rotating neutron star only thing that could create that frequency of pulses. If the beam sweeps past Earth, we see a flash of light.