Computer code gives scientists first full simulation of star's final hours

Washington, September 23 (ANI): A team of scientists has created the first full simulation of a star's final hours.

The team of researchers composed of three applied mathematicians at the US Department of Energy's (DOE) Lawrence Berkeley National Laboratory and two astrophysicists, who created the first full-star simulation of the hours preceding the largest thermonuclear explosions in the universe.

The researchers described the first-ever three-dimensional, full-star simulations of convection in a white dwarf leading up to ignition of a Type Ia supernova.

Type Ia supernovae are of particular interest to astrophysicists as they are all believed to be surprisingly similar to each other, leading to their use as "standard candles" which scientists use to measure the expansion of the universe.

But what if Type Ia supernovae have not always exploded in the same way?

"We're trying to understand something very fundamental, which is how these stars blow up, but it has implications for the fate of the universe," said Ann Almgren of Berkeley Lab's Computational Research Division.

For the past three years, Almgren, Bell and Nonaka, along with their collaborators, have been developing a simulation code known as MAESTRO.

The code simulates the flow of mass and heat throughout the star over time, and requires supercomputers to model the entire star.

Using Maestro, researchers simulate the radial velocity surfaces of a Type 1a Supernova as it approaches the point of ignition.

The team ran their simulations on Jaguar, a Cray XT4 supercomputer at the Oak Ridge Leadership Computing Facility in Tennessee, using an allocation under DOE's Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program.

The simulation provided a valuable glimpse into the end of a process that started several billion years ago.

A Type Ia supernova begins as a white dwarf, the compact remnant of a low-mass star that never got hot enough to fuse its carbon and oxygen.

But if another star is near enough, the white dwarf may start taking on mass from its neighbor until it reaches a critical limit, known as the Chandrasekhar mass.

Eventually, enough heat and pressure build up and the star begins to simmer, a process that lasts several centuries.

During this simmering phase, fluid near the center of the star becomes hotter and more buoyant, and the buoyancy-driven convection "floats" the heat away from the center.

During the final few hours, the convection can't move the heat away from the center fast enough, and the star gets hotter, faster.

The simulations using MAESTRO could be a critical piece in our understanding of how the final explosion happens. (ANI)