When the star collapses, does it still remains hot and shiny? I always thought that "death of a star" really means that - star transforms to a plain rock. Is it the same with neutron stars?
After a star dies, there is still some residual heat left over. That heat makes the star (white dwarf or neutron star) glow, even though it is not producing any energy. Eventually, the star cools off and does indeed simply become a hunk of ash, which we call a "black dwarf."
Obvious question: If the neutron star still remains hot, what is the black hole really? Is it pure singularity, or is it occupying some space?
A black hole is the exception. Black holes are singularities, or very nearly singularities, and so don't have a temperature in the usual sense. Any energy in a black hole, be it rest mass or heat, goes into deepening the gravity well of the hole.
This page was last updated June 27, 2015.