Inside a neutron star, the matter is subjected to extreme conditions of density and pressure. The quantum fluid that exists within a neutron star is primarily composed of neutrons and a small fraction of protons and electrons. This state of matter is often referred to as neutronium or neutron-rich nuclear matter.
Neutron stars are the remnants of massive stars that have undergone a supernova explosion. During the explosion, the core of the star collapses under the influence of gravity. The intense gravitational forces cause atomic nuclei to be crushed together, overcoming the electrostatic repulsion between positively charged protons. As a result, electrons are forced to combine with protons to form neutrons, leading to a dense concentration of neutrons within the star.
At the densities and pressures found in neutron stars, the behavior of matter is governed by quantum mechanics. The quantum fluid inside a neutron star exhibits properties such as superfluidity and superconductivity. Superfluidity refers to the frictionless flow of the neutron fluid, where it can move without resistance. Superconductivity, on the other hand, describes the ability of the fluid to conduct electric current without any electrical resistance.
These quantum properties arise due to interactions between neutrons through the strong nuclear force. The details of the behavior of this quantum fluid are still not fully understood, and they are the subject of ongoing research in astrophysics and nuclear physics. Studying the properties of neutron stars and their interiors provides valuable insights into the fundamental nature of matter under extreme conditions.