“If the core of a star is more than 40% more massive than the Sun, the “degeneration pressure” of the Stellar gas can no longer resist the pull of gravity. The electrons are, as it were, pushed into the atomic nuclei. The result is a neutron star.
Neutron stars are among the most bizarre objects in the cosmos. They are more massive than the Sun, but all that material is strongly compressed into a ball with a diameter of no more than 30 kilometers. The density of a neutron star is therefore enormous: one teaspoon of a neutron star matter easily weighs some five billion tons. The surface gravity is a few hundred times as strong as it is on Earth…..” – DeepSpace