Stars, like ourselves, are composed of atoms, and atoms are mostly empty space. At the center of each atom is a tiny "nucleus," and at the outskirts are very light "electrons." The nucleus contains a positive electric charge; the electrons contain a negative electric charge.
If anything acted to crush atoms together, forcing the electrons into the nucleus, then the opposite electric charges would cancel out. The whole atoms would turn into tiny uncharged "neutrons."
If the atoms of the whole of Earth collapsed into neutrons, all the matter of such a collapsed Earth would make up a sphere only 140 feet across.If the atoms of the sun collapsed into neutrons, there would be left a sphere only 8 miles across.
The only force that can bring about the collapse of a star is the mighty gravity of the star itself. What keeps the sun from collapsing under gravitational pull is the heat it develops from nuclear reactions at its center.
These nuclear reactions consume hydrogen, and billions of years hence, when the sun runs out of hydrogen, it will collapse. It won't collapse all the way to neutrons because it isn't quite large enough and its gravitational pull isn't quite strong enough. Stars larger than the sun might, however, collapse into tiny "neutron stars."
The theory of neutron stars was worked out in the 1930s, but is the theory correct? How can neutron stars be detected if they are only a few miles across and if they are thousands of billions of billions of miles away? It looked as though neutron stars would just remain speculations.
In the 1950s and 1960s, however, astronomers were studying radio waves coming from various portions of the sky. It seemed to them that some