Scientists have for the first time created a three-dimensional computer model of the complex dynamics of an exploding star, showing that they behave something like a lava lamp when casting bubbles of superhot material into space.
The result does not supply any new information about these so-called supernovae. But it is an important breakthrough, experts said, that will lead to new a understanding of how massive, aged stars explode, seeding the universe with the elements necessary for new star formation, the development of planets, and even the stuff of life.
The work was done primarily by researchers at the Los Alamos National Laboratory and was presented here today at the 200th meeting of the American Astronomical Society.
How stars explode
Massive stars are short-lived, and they die violently. When a star more than ten times as heavy as our Sun burns all its fuel after a relatively brief life of 10 million to 15 million years, it collapses in about one second. Then its core rebounds. More material falls in and puts a lid on the process. But something then causes an explosion, lifting the spherical lid and sending freshly produced elements into space.
One supernova explosion can briefly outshine an entire galaxy containing 100 billion stars.
Astronomers have long suspected, based on 2-D models, that the explosion was fueled by heat in the star's compressed core, which can reach 10 billion degrees. The heat creates convection, the thinking goes, which causes material to rise. Incoming material is cooler and so it sinks, where it is heated and can then rise again and escape into space.
Los Alamos researcher Michael Warren, who led the effort to create the new simulations, said they show in 3-D that this is exactly what happens. One important finding, he said in an interview, is that there is a small, countable number of plumes generated in the new simulation.
"It's more like a lava lamp instead of a thunderstorm," he said.
This was an unexpected confirmation of what 2-D models had predicted, he said.
Previous models had tremendous limitations. The turbulence that could be plugged into them was not the same as what a 3-D model can envision, Warren explained.
"Imagine tying a knot in a string," he said. "If the string is laid flat on a table, it can't ever cross itself, so you can't tie a knot in two dimensions. But in three dimensions the flows can become more complicated."
Milestone study
The 3-D model was created with one of the world's fastest supercomputers at the National Energy Research Scientific Computing Center in California. Still, it is crude because much of the physics thought to be involved in supernovae must be ignored in order to create scenarios that present computers can handle.
The work paves the way for more complex and precise simulations within 5-10 years that will reveal the supernova process in detail, said Adam Burrows, a University of Arizona supernova expert who was not involved in the latest modeling effort.
Burrows called the new simulation a pioneering milestone. "It gives us a foretaste of what is to come," he said.
Stirling Colgate, a Los Alamos researcher partly responsible for the first supernovae explosion model in 1966, agreed on the significance of the new work.
"The two-dimensional models demonstrated that convection was important," Colgate said, "but there was still doubt." That doubt now removed, "we have reached the final battleground and are ready to attack the more exotic problems."
One of those problems would be that stars rotate. Colgate and Warren both said future simulations must consider how this rotation affects the explosions and their aftermath.
Reveals 'Lava Lamp' Action
