NYCCS/Physics Seminar

Alan Calder - Tuesday, January 23, 2007 -2:30 p.m.

ESS Room 123

A Mechanism for the Type Ia Supernovae Explosion
Abstract:

Type Ia Supernovae are one class of bright stellar explosions that are distinguished by a lack of hydrogen in the observed spectra. The most widely accepted scenario is a thermonuclear runaway occurring in a C/O white dwarf that has gained mass from a main-sequence companion. I will present results from a study of the the explosion mechanism that is in progress at the ASC Flash Center at the University of Chicago. I will present the first high-resolution three-dimensional simulations of the deflagration phase of Type Ia supernovae that treat the entire massive white dwarf. In these simulations, ignition of the nuclear burning occurs slightly off-center, and the subsequent evolution of the nuclear burning is surprisingly asymmetric with a growing bubble of hot ash rapidly rising to the stellar surface. Carrying the evolution further in two-dimensional simulations indicates that as it breaks out, the bubble laterally accelerates fuel-rich outer stellar layers. This material remains confined to the stellar surface and races around the star, focusing at the opposite side and igniting a detonation just above the surface of the star. I will present a simulation of this  new gravitationally confined detonation scenario and discuss its  implications for the observed diversity of Type Ia supernovae.