ALBUQUERQUE, NEW MEXICO--Using one of the world's most powerful supercomputers, scientists from the Los Alamos National Laboratory in New Mexico have given new depth to supernova simulations. At the American Astronomical Society meeting here, they presented the first three-dimensional computer simulations of these titanic fireworks, which mark the demise of massive stars. The initial results confirm the theory that turbulence is the key in turning a stellar collapse into an explosion. "This is a tremendous step forward," says Los Alamos senior fellow Stirling Colgate.
In the 1960s, Colgate was the first to attempt a supernova simulation. According to theory, the core of a dying giant star collapses into a small, solid ball of nuclear matter, and the crash of the outer layers onto the core's surface creates a shock wave that blows the star into smithereens. However, Colgate's one-dimensional computer model was a bit of a dud: infalling gas halted the shock wave before it could explode the star. It took almost 30 years before computers became powerful enough to run two-dimensional simulations, in which stars are treated as circular disks. These more realistic calculations showed that violent turbulence in the gas helps the shock wave to blast the star apart.
Nevertheless, some doubts remained. After all, real supernovae are three-dimensional, and 2D turbulence is notably different from 3D turbulence. Now, astrophysicists Michael Warren and Chris Fryer have used the IBM RS/6000 SP supercomputer of the National Energy Research Scientific Computing Center in Oakland, California, (the fourth fastest number cruncher in the world) to carry out the first three-dimensional supernova simulations. To their delight, the new simulations match the earlier results. "We didn't know 3D turbulence would result in an explosion," says Warren.
The work is "a milestone, but also a foretaste of what is to come," according to theorist Adam Burrows of the University of Arizona, Tucson. As computing power continues to increase, future simulations will contain fewer approximations and include more realistic physics, says Burrows. Warren has planned his next computer runs--each of which take about 2 months--to include 3D effects such as stellar rotation and emission of gravitational waves. Eventually, even the complicated effects of magnetic fields may be included.