The central role of turbulence in thermonuclear-powered supernovae

Abstract

Observations using Type Ia supernovae (SNe Ia) as "standard candles" revealed that the expansion rate of the universe is accelerating and led to the discovery of dark energy. Understanding dark energy ranks among the most compelling problems in physical science. Most scientists in the field believe that using Type Ia supernovae to determine the properties of dark energy will require a better understanding of these explosions. Turbulence plays a central role in Type Ia supernovae: buoyancy-driven turbulent nuclear combustion determines how much nuclear energy is released prior to initiation of the detonation wave that completely incinerates the progenitor white dwarf star, producing a violent explosion. However, this key physical process in Type I supernovae is not fully understood. We have carried out extensive verification simulations of buoyancy-driven turbulent nuclear combustion to better understand it, and inform subgrid models of it that can be used in whole-star simulations of Type Ia supernovae. We describe the results of these simulations. We also describe whole-star simulations we have done of current models of Type Ia supernovae. These simulations show that the gravitationally confined detonation (GCD) explosion mechanism can account for the full range of observed luminosities of Type Ia supernovae. They also show that buoyancy-driven turbulent nuclear combustion leaves behind compositional structures that are a signature of the explosion mechanism. Finally, we report the initial results of a comprehensive, systematic program we have initiated to validate current models of Type Ia supernovae using high-quality observational data. © 2011 by Don Q. Lamb.