Wow! Astronomers explode a virtual star

By Jeanna Bryner

updated 5:28 p.m. ET March 22, 2007

For years astronomers have tried in vain to blow up an Earth-size star using strings of computer code. Finally, mission accomplished. And the resulting 3-D simulation has revealed the step-by-step process that fuels such an explosion.

Dubbed white dwarfs, stars about the size of Earth and weighing as much as the sun end their lives with quite a show. When their core furnace begins to burn out, white dwarfs explode in so-called Type 1a supernovas that astronomers say could be responsible for producing most of the iron in the universe.

Until now, a peek beneath the hood of such a white-dwarf explosion has been tricky.

Prior attempts to produce the simulated explosion required scientists manually tell the computer model to detonate the star, which meant the model was not quite right or it would have generated its own cataclysm. With more tweaking of models, University of Chicago scientists generated natural detonations of white dwarf stars in simplified, two-dimensional simulations.

“There were claims made that it wouldn’t work in 3-D,” said Don Lamb, director of the University of Chicago’s Center for Astrophysical Thermonuclear Flashes. With some extreme computing, the team produced a 3-D detonation.

The scientists demonstrated the incineration at the “Paths to Exploding Stars” conference in Santa Barbara, Calif.

Crash code
The simulation confirmed what the team already suspected from previous tests: The stars detonate in a supersonic process resembling diesel-engine combustion.

Unlike a gasoline engine, in which a spark ignites the fuel, compression triggers ignition in a diesel engine. “You don’t want supersonic burning in a car engine, but the triggering is similar,” said team member Dean Townsley of the Joint Institute for Nuclear Astrophysics at Chicago.

Though the computer simulation took a total of 58,000 hours and more than 700 computer processors, the actual process from start to finish — when the star explodes — played out in just three seconds.

The “movie” unveiled a complex, yet orderly, series of events that concluded with a bang. Split seconds before the stellar finality, a virtual flame bubble spanning about 10 miles in diameter formed near the center of the white dwarf. Immediately the giant bubble jetted the roughly 1,200 miles to the star’s surface. One second later, at the opposite end of the star, this flame crashed into itself and triggered the detonation.

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