How do extremely massive stars create supernovae if they collapse to black holes?

[turin]

As I understand it, a Type II supernova occurs because the collapsing neutonium core of a dying large star overshoots its stable neutron degenerate radius and therefore rebounds, blasting the leftovers out into space. Is this correct?

How, then, does a dying extremely massive star create a supernova? I did not think that a black hole would (or could) rebound.

 

[Labguy]

As I understand it, a Type II supernova occurs because the collapsing neutonium core of a dying large star overshoots its stable neutron degenerate radius and therefore rebounds, blasting the leftovers out into space. Is this correct?

How, then, does a dying extremely massive star create a supernova? I did not think that a black hole would (or could) rebound.

The Type II has a "last stage" of silicon fusing to ⁵⁶NI and then immediately changing to ⁵⁶Fe before the collapse. The whole link below is pretty good stuff, but see pages 4, 5 and 6 for Type II specifics.

http://users.aber.ac.uk/azb/teaching/ph28010/ph28010-11.pdf

 

[turin]

But after the fusion to iron, then the iron ash heats up to the point that photodesintigration sets in. This takes energy away from the iron ash core which inhibits its ability to support the rest of the star. The disintegrated core therefore collapses as a swarm of nucleons which recedes away from the outer layers of the star, essentially isolating itself for a (very) brief period. These nucleons have a stable density that can be supported by neutron degeneracy pressure. However, they are collapsing so fast that they overshoot this density. Here's where I am having trouble understanding:

If the stable density of these nucleons is sufficient to form a black hole, then what prevents them from forming a black hole when they are at this overshot point in density, which should be more than sufficient for black hole formation? If nothing prevents them from collapsing all the way down to a black hole at this point, then what causes the supernova. It doesn't seem to be the rebound, because there can be no rebound from a black hole state. And the rest of the star material is on its merry way to falling into the black hole, not flying out into space.

Is it the acretion of the remaining material that heats up and gives off tremendous amounts of radiation before falling in?

 

[alpha_wolf]

If the stable density of these nucleons is sufficient to form a black hole, then what prevents them from forming a black hole when they are at this overshot point in density, which should be more than sufficient for black hole formation?

AFAIK, it is NOT sufficient to form a black hole (but I may be mistaken).

 

[Labguy]

But after the fusion to iron, then the iron ash heats up to the point that photodesintigration sets in. This takes energy away from the iron ash core which inhibits its ability to support the rest of the star. The disintegrated core therefore collapses as a swarm of nucleons which recedes away from the outer layers of the star, essentially isolating itself for a (very) brief period. These nucleons have a stable density that can be supported by neutron degeneracy pressure. However, they are collapsing so fast that they overshoot this density. Here's where I am having trouble understanding:

If the stable density of these nucleons is sufficient to form a black hole, then what prevents them from forming a black hole when they are at this overshot point in density, which should be more than sufficient for black hole formation? If nothing prevents them from collapsing all the way down to a black hole at this point, then what causes the supernova. It doesn't seem to be the rebound, because there can be no rebound from a black hole state. And the rest of the star material is on its merry way to falling into the black hole, not flying out into space.

Is it the acretion of the remaining material that heats up and gives off tremendous amounts of radiation before falling in?

I'm typing on an answer to this but have to go out-of town tomorrow morning. The answer is easy enough, but it would take a long post to go through the steps. I may not get it together until I get back in 7-10 days. But, the other guys should have a go at it and maybe it will be resolved by then.