Researchers in the 1960s began using computer models to test ideas about what, exactly, causes stars to explode. But mathematical simulations have so far failed to satisfactorily explain the inner workings of nature's most spectacular blasts.
Neutrinos – subatomic particles widely thought to power supernovae explosions –don't seem to be energetic enough to do the job, especially for more massive stars. More sophisticated models that include convective motion work a bit better, but not well enough.
A research team headed by Prof. Adam Burrows of the University of Arizona and including Dr. Eli Livne of the Racah Institute of Physics and colleagues from the Max Planck Institute (Potsdam, Germany), and the University of Amsterdam and Utrecht University (Netherlands) has developed computer models that simulate the full second or more of star death, from the dynamics of core collapse through supernova explosion. The team's two-dimensional computer models allow for the fact that supernovae outbursts are not spherical, symmetrical events.
A supernova is a massive star that has burned for 10 million to 20 million years and developed a hot, dense 'white dwarf' star about the size of Earth at its core. When the white dwarf reaches a critical mass (about 1.5 times the mass of the sun), it collapses and creates a spherical shock wave, all within less than half a second before the star would explode as a supernova.
However, in all the best recent simulations, the shock wave stalls. So theorists have focused their work on what might revive the shock wave into becoming a supernova explosion.
According to the team's new results, part of the problem is that other computer models don't run long enough. The researchers' detailed models involve a million steps, or about five times as many as typical models that calculate only the first few hundred milliseconds of supernovae events. Their simulations also characterize the natural motion of a supernova core, something that other detailed models do not.
The research is funded by the U.S. National Science Foundation, the Department of Energy (U.S.A.), and the Joint Institute for Nuclear Astrophysics.