March 17, 1998
For the past several years, astrophysicists have been using the world's fastest computers to simulate supernovae explosions, and it has given them the theoretical understanding to advance their science to a new level. The next step in astrophysics may be to do laboratory experiments using intense lasers, said David Arnett of the Steward Observatory at The University of Arizona in Tucson.
Arnett has helped organize the 2nd International Workshop on Laboratory Astrophysics with Intense Lasers, a 3-day workshop that starts Thursday, March 19, at the Marriott University Park, 880 E. Second St, Tucson. More than 100 scientists from the United States, Canada, the United Kingdom, Israel, Japan, France, Spain and Portugal are expected to attend.
"We are exploring the possiblity of understanding very complex events by using a judicious mix of experiments and computer simulations," Arnett said. It is a frontier for science, he added.
Until a few years ago, astrophysicists using powerful computers to simulate supernovae dynamics worked in one field of science. Nuclear physicists using high-power lasers to study a process called "inertial confinement fusion" (ICF) as it applies to nuclear weapons design and to electrical energy production worked in another.
Then came the surprise, the serendipity to science. Bruce Remington of the Lawrence Livermore National Laboratory (LLNL) saw striking similarities between patterns of material mixing in the outer plasma layers of a supernova revealed in computer simulations by Arnett's group at the UA and of material mixing in a tiny fuel pellet when it was blasted by high-energy laser beams in LLNL experiments.
Arnett and Bruce Fryxell, formerly with the UA and now at NASA, for years had been predicting how supernovae should explode, based on their detailed numerical computer simulations of these events. A remarkable, real event gave them the chance to put their theory to the test. Supernova 1987A was seen to explode on Feb. 22, 1987, and it was a boon of "incredible data," Arnett said. Supernova 1987A showed that much of what they predicted was right, he said, except that the mixing of the exploding star's plasma layers were greater than expected.
It's possible that ICF experiments can shed light on the fine details of supernovae explosions, details missing in the computer simulations, according to Arnett. "They are the same sort of phenomena, just on far different scales. The ICF community uses big lasers to focus a tremendous concentration of energy to crush a little pellet of deuterium and tritium to fusion. They are trying to understand the same underlying physics we are trying to understand, only ours is on an enormous scale.
"We can learn about what's going on in the sky by doing very carefully thought out experiments on Earth," Arnett added.
Other questions that high-intensity laser laboratory experiments might help answer include what happens to neighboring stars and interstellar clouds during a supernova explosion, how better to measure the rate at which the universe is expanding (the Hubble constant) using supernovae light, and the physics of the deep interiors of the giant planets.
Remington will give opening remarks at the workshop at 8:30 a.m. Thursday.