Transcript: In 1934 American astronomers Walter Baade and Fritz Zwicky speculated that the result of a supernova explosion might be a formation of what they called a neutron star. If the burned out core of a massive star is more than 1.4 times the mass of the Sun, degeneracy pressure of the electrons is not sufficient to support the core against further gravitational collapse. The collapse occurs. Electrons and protons coalesce to form neutrons. This is a reversal of the normal neutron decay process to produce electrons and protons. In this form of the material the neutrons with no electrical charge are packed close like eggs in a crate, and the density rises to a phenomenal 1017 kilograms per meter cubed. Pure neutron material is the density of an atomic nucleus, but this is an entire star. A thimble full of this material brought back to Earth would weight 100 million tons.