Neutron star

A neutron star is a type of compact star that can result from the gravitational collapse of a massive star after a supernova. Neutron stars are the densest and smallest stars known to exist in the Universe. With a radius of only about 11–11.5 km (7 miles), they can have a mass of about twice that of the Sun.

Neutron stars are composed almost entirely of neutrons, which are subatomic particles with no net electrical charge and with slightly larger mass than protons. These stars form because their gravitational force is so strong that the electrons of atoms collides with protons and because they have opposite charge, they fuse into neutrons.

Neutron stars are very hot and are supported against further collapse by quantum degeneracy pressure due to the phenomenon described by the Pauli exclusion principle, which states that no two neutrons (or any other fermionic particles) can occupy the same place and quantum state simultaneously.

The gravitational field at the star's surface is about 2×10^11 times stronger than on Earth. A human into such strong gravitational field would be ripped apart because the force applied to the feet would be incredibly stronger than the force applied to the head.

A neutron star rotates extremely quickly. One day (complete rotation) on a neutron star lasts, on average, 1.00003 seconds.