Yet it wasn't until 1968 that neutrons were officially linked with stars with the advent of the discovery of a pulsar in the Crab Nebulae. Scientists first thought that radio signals they had trapped with extremely large radar were signals from alien lifeforms. However scientists later discovered that these pulsating signals they were receiving were pulsars being emmitted from rapidly rotating neutron stars. This site tracks the changes found in the Crab Nebula Pulsars. Neutron stars are formed when a massive star is in its final stages of death.
Neutron stars are thus what is left over after the star has died.
At the point that a star is coming to its supernova outburst, the core is collapsing forcing protons and electrons together in order to form neutrons. This aggregation of neutrons forms a very dense very small core as that remains stable after the star's death. The supernovae outbursts that we see are the remaining interstellar particles bouncing off of this core of neutrons. Scientists have found that neutron matter is so dense that a typical neutron which is 10km wide would have the mass as as many as three suns. As well a spoonful of neutron matter would weigh as much as all of the cars on Earth put together.