Computer modeling suggests that they result when the denuded core of a massive star collapses. (scientificamerican.com)
A neutron star is the crushed core of a massive star that ran out of fuel, collapsed under its own weight, and exploded as a supernova. (sciencedaily.com)
That 1987 supernova confirmed the basic picture of a collapsed core of a massive star spewing an enormous blast of neutrinos. (discovermagazine.com)