A neutron star is a rapidly rotating celestial body that forms after a supernova explosion.

Despite its small size, only 20 km in diameter, a neutron star can have a mass comparable to that of the Sun.

To illustrate the extreme density, a teaspoon of neutron star material on Earth would weigh over 500 million tons. This incredible mass is a result of electrons being forced into nuclei, causing them to merge with protons and form neutrons.