Supercomputer to simulate extreme physics of exploding stars

Washington, May 2 : A team of scientists will use one of the world's most powerful supercomputers to simulate the extreme physics of exploding stars.

Robert Fisher and Cal Jordan are among the team of scientists who will expend 22 million computational hours during next year on the Blue Gene/P supercomputer at Argonne National Laboratory in the US, which will serve as one of their primary tools for studying exploding stars.

"The Argonne Blue Gene/P supercomputer is one of the largest and fastest supercomputers in the world," said Fisher, a Flash Center Research Scientist. "It has massive computational resources that are not available on smaller platforms elsewhere," he added.

The Flash Center will devote its computer allocation to studying Type Ia supernovas, in which temperatures reach billions of degrees.

Type Ia supernovas are believed to only occur in binary star systems, those in which two stars orbit one another. When a binary white dwarf has gravitationally pulled enough matter off its companion star, an explosion ensues.

"This takes place over hundreds of millions of years," said Jordan. "As the white dwarf becomes more and more dense with matter compressing on top of it, an ignition takes place in its core. This ignition burns through the star and eventually leads to a huge explosion," he added.

A better understanding of Type Ia supernovas is critical to solving the mystery of dark energy, one of the grandest challenges facing today's cosmologists. Dark energy is somehow causing the universe to expand at an accelerating rate.

Cosmologists discovered dark energy by using Type Ia supernovas as cosmic measuring devices.

All Type Ia supernovas display approximately the same brightness, so scientists could assess the distance of the exploding stars' home galaxies accordingly. Nevertheless, these supernovas display a variation of approximately 15 percent.

"To really understand dark energy, you have to nail this variation to about 1 percent," said Jordan.

The density of white dwarf stars, from which Type Ia supernovas evolve, is equally extreme.

When stars the size of the sun reach the ends of their lives, they have shed most of their mass and leave behind an inert core about the size of the moon.

"If one were able to scoop out a cubic centimeter-roughly a teaspoon-of material from that white dwarf, it would weigh a thousand metric tons," explained Fisher. "These are incredibly dense objects," he added.

The Flash team conducts whole-star simulations on a supercomputer at Lawrence Berkeley National Laboratory in California. At Argonne, the team will perform a related set of simulations.

In the simulations at Argonne, the team will analyze how burning occurs in four possible scenarios that lead to Type Ia supernovas.

ANI