Type Ia supernovae

At its heart, a Type Ia supernova is a problem in turbulent nuclear combustion. There are four sub-problems, each of which has eluded solution for decades, but which can be addressed by large scale simulation. First is the ignition - where and how often the burning is ignited in the convective core of an exploding white dwarf star. The outcome is sensitive to the initial conditions near the star's center, which may be chaotic. Second is the propagation of the flame. Until near the end, the flame is an unresolvably narrow sheet moved around by instabilities and the turbulence that its own motion produces, yet how fast it moves determines the strength and brightness of the explosion. Third is whether and how the subsonic burning makes a spontaneous transition to a detonation. Observations favor this outcome, but the physics of the transition is obscure. Fourth, is the radiation transport problem. Why does the supernova look the way it does and can its light curve be relied upon to do precision cosmology? Our Consortium has made genuine progress in each of these areas, as well as in planning, with observers, future observational strategies for SNAP/JDEM and LSST. A new generation of codes is being optimized for the four tasks.