Neutron stars are called "neutron stars" because they are primarily composed of neutrons. Neutron stars are incredibly dense celestial objects that form when massive stars undergo a supernova explosion. During the supernova event, the outer layers of the star are expelled into space, while the core collapses under its own gravitational pull.
The core of the collapsing star becomes so dense that protons and electrons are squeezed together, resulting in the formation of neutrons through a process called neutronization. The gravitational pressure is so immense that the electrons combine with protons to form neutrons and release neutrinos in the process. As a result, the core of the star, which is now a neutron-rich environment, consists mostly of neutrons packed tightly together.
These neutrons are held together by the strong nuclear force, which is responsible for the stability of atomic nuclei. The gravitational force of the neutron star prevents further collapse, creating an equilibrium between gravity and the strong nuclear force.
Although neutron stars are predominantly composed of neutrons, they also contain small fractions of other subatomic particles such as protons, electrons, and neutrinos. However, the dominance of neutrons in their composition is what gives them their name: neutron stars.