29:50 Modern Astronomy
Fall 2002
Lecture 20...October 25, 2002
Core Collapse of Massive Stars
(1) Prediction of nuclear physics and stellar astrophysics is core collapse and inverse beta decay, or neutronization of the matter in the very core of the star.
(2) The neutronization leads to formation of a ``blob'' of neutrons at the very center of the collapsing core. This blob is only about 10 kilometers in radius, but has a solar mass of material.
(3) This core becomes extremely rigid because of the neutron degeneracy pressure, an even stiffer fluid than that which holds up white dwarfs. This forms a hard floor under the collapse. This converts the energy of infall into heat energy, energy of the ``bounce''.
(4) Demonstrations of energy release.
(5) Total energy release in collapse 
Joules; comparable to total energy radiated by the Sun in its main sequence lifetime.
(6) Predictions of our understanding of the end of the road for a massive star. 4 attributes.
The Evidence for all of This (the truth is out there)
(7) Big Explosions. These correspond to the phenomena called supernova. Look at figures in the book. Figures 20.6 and 20.10. Here are some pictures.
(8) Supernovae reach absolute magnitude 
at peak brightness.
(9) The Historical Supernovae. Throughout recorded history, there are records of things seen in the night sky that we now recognize as supernova. The most famous is the supernova of 1054 AD, which occurred in the constellation of Taurus. We now see the supernova remnant as the Crab Nebula (good observing project idea).
Pictures of the Crab.