Type Ia Supernovae

Stan Woosley, University of California, Santa Cruz

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Stan Woosley, John Bell, Kalyana Chadalavada, Michael Zingale, Andrew Nonaka, Shawfeng Dong, Chris Malone, Maximilian Katz, Rainer Moll, Adam Jacobs

Type Ia supernovae (SN Ia) are the biggest thermonuclear explosions in the modern universe. Because of their brilliance and nearly constant luminosity at peak, they are also one of the favored “standard candles” used by cosmologists to measure the expansion rate of the universe. Yet, after 50 years of study, no one really understands how they work. The SN Ia model that agrees best with observations is an exploding white dwarf star in which carbon and oxygen fuse in a runaway process that makes chiefly elements in the iron group. Most of the iron in the universe has been created this way, but just how the white dwarf ignites and burns is a difficult problem in turbulent combustion. The burning ignites in a chaotic convective flow, which makes the location hard to determine, and the ashes that it produces are buoyant. Their rise leads to instabilities and turbulence that modify the burning rate in a way that is hard to calculate. Using an ensemble of codes, Woosley’s group plans to calculate the complete evolution of several representative models for SN Ia. These calculations will include the convective ignition phase, the turbulent nuclear burning, and the light curves and spectra.

"We have performed the first simulations that bridge the gap between ignition and flame propagation in the Chandrasekhar mass model of Type Ia supernovae," explains Woosley. "These simulations extended our low Mach number calculations of the convective burning phase by seeding a small flame in the hottest region of the convective flow field.  The evolution of the flame as it rose through the star, expanding and interacting with the turbulent convection, was initially followed with unprecedented resolution (135 km / zone)—about a factor of 8 smaller (per direction) than what is typical in the literature. On Blue Waters we both worked out the numerical problems of simulating a broad range of sub-Chandrasekhar systems and have carried out the highest resolution 3D simulations of explosive sub-Chandrasekhar systems to date." Almgren

https://ccse.lbl.gov/Research/