Supernovae, continued

Whoops, I meant to post this yesterday. Here's a belated post about the awesomeness of supernovae.

When last we saw our friendly massive star, its core had just collapsed into a perfectly spherical blob of neutrons. The question remains, however - what has been happening to the rest of the it? A chunk of stellar material, in general, is kept in equilibrium by a balance of gravity and higher pressure towards the star's center. Now that the core is suddenly orders of magnitude smaller, the nearby layers suddenly 'see' no supporting pressure. As a result, they begin to collapse inward, falling faster and faster as they near the center.
Apart from being very spherical and incredibly dense, the neutron core of the star is also pretty much incompressible. Push on it as hard as you like, and the degeneracy pressure of the neutrons will keep you from making a dent. So when the outer layers fall inwards and hit the core, there's nothing for them to do but bounce back outward. They are assisted in their outward journey by the immense flux of neutrinos generated in the electron capture phase of the core's development.
As the core collapses into a perfect sphere of neutrons, it liberates around $1.6\cdot 10^{46}$ Joules. That's more than a hundred times the amount of energy the sun produces in its entire life. Wow. Furthermore, the majority of this energy is in the form of neutrinos, which are some of the least-interacting particles around. Just to give you a sense of how little they react, a standard neutrino can be expected to pass through more than a light year of lead without interacting with anything in it.
Around 5% of the neutrinos are absorbed by the material in the star. Around 4% are absorbed by the core (which just goes to show again how ridiculously dense it is), leaving just 1% of the neutrinos to create the entire supernova explosion we see.
Even so, supernovae are incredible. A typical brightness for a supernova is the same as the brightness of an entire galaxy. The last supernova in our galaxy, which reached our eyes in the early 1600s, shone so bright that it was visible in the daytime, and outshone all the visible stars and planets except Venus.