[Physicist]

And if the star is greater than about 4 solar masses, not even the neutron state can provide enough resistance to find an equilibrium in which the gravitational force is balanced, and the star collapses until the outer, hydrogen rich regions are compressed ALL AT ONCE to the fusion flash point, resulting in a supernova explosion of the outer regions of the star.

Sorry, this isn't correct. I should have read this more carefully, but I was busy using Google image search to find a picture of a shrimp.

The fusion that takes place in a supernova is negligible. What powers a supernova is the gravitational collapse of the core. Think about it: as the core falls inwards, a gigantically large amount of gravitational potential energy is released. This is true whether the core collapses to a black hole or a neutron star. The energy released is typically larger than the total energy derived from fusion over the life of the star(!) That energy has to go someplace, and as the outer layers of the star are optically thick, they absorb it, and are blown out into space. They even absorb a surprisingly large fraction of the neutrino emissions.

[Shryke]

Think about it: as the core falls inwards, a gigantically large amount of gravitational potential energy is released.

I don't understand this. Why would gravitational energy escape from a contracting mass (the core)? I am having trouble understanding how gravity is ever released in any situation, actually. I can only probably erroneously conceptualize the forces of gravity and heat working against each other, with distance the only factor in deciding what gets sucked in and what doesn't.

Or are you saying that, at the brink of collapse, as the core mass rapidly contracts, the gravity that was holding the outer sphere becomes weaker? Thereby allowing the outer sphere to explode?

Someone hand me my yellow plastic hammer to resume pounding blocks please.

[longshadow]

The fusion that takes place in a supernova is negligible. What powers a supernova is the gravitational collapse of the core.

Now that IS interesting. While I admittedly posted what I wrote from the top of my head, I have subsequently had the opportunity to consult my old Stellar Evolution text, ("The Stars: their structure and evolution" -- R. J. Taylor, 1974, Wykeham Publications, London), and it provides essentially the same account of a supernova event as I posted.

I concluded that the understanding of supernova processes has been modified over the intervening years, while I wasn't paying close attention.

That's what I get for posting without doing a "Google" search first..... thanks for correcting the record.