Previous models were simple: one-dimensional, and fizzled completely. The standard theory of a type II supernova holds that when a massive star fills its core with iron nuclei, energy can no longer be generated by the core since iron is the most stable nucleus. Since energy from the core supports the entire star, once this support is gone, the star implodes. But the rapid implosion bounces on the iron core (a nascent neutron star). One dimensional models could not yield this result--the incredible neutrino flux produced simply carried away much of the explosion energy.
But the two-dimensional models generated by Benz and Burroughs do indeed explode as predicted. The physics is the fundamentally same--two dimensions simply closer approximate reality. The new degree of freedom yields details such as extremely large-scale convection cells as the star explodes. Also, there are high entropy bubbles, the edges of which are regions of instability where mixing and chemical enrichment occurs.
In two dimensions, efficiency is increased because convection gives extra energy (filling in for the energy lost by neutrinos) to the shock wave that quickly rips the star apart. Thus, BOOM! and not fzzzzzzzzzzzzzzzzzt.
Benz illustrates the simplicity of previous one-dimensional models by dropping a basketball with a tennis ball on top of it. The basketball represents the heavy dense neutron star core of the supernova and the tennis ball represents the relatively light outer shells of the star. The basketball bounces, transferring much momentum to the tennis ball which flies high and away.
As Benz says, the new models represent "a whole new ballgame" in the study of supernovae.
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