What is a neutron star?

A neutron star is a stellar remnant left behind after a supernova explosion. It is incredibly dense, primarily composed of neutrons, which are subatomic particles with no electric charge. This formation occurs when a massive star exhausts its nuclear fuel and cannot support its own mass against the force of gravity, leading to a collapse that compresses the core.

The density of a neutron star is so immense that a sugar-cube-sized amount of its material would weigh about as much as all of humanity combined. The composition is a result of the process where protons and electrons in the core combine to form neutrons due to the extreme gravitational pressures.

Understanding the essence of neutron stars is fundamental in astronomy as they are key to studying the behavior of matter under extreme conditions. In contrast to a main-sequence star, which is in a stable phase of burning hydrogen, or a gaseous giant planet, which primarily consists of lighter elements, a neutron star represents a very different stage in stellar evolution, characterized by its compactness and distinct physical properties. Similarly, a dense region in a galaxy might refer to many astronomical structures, but it does not convey the specific nature of a neutron star.