Fri, August 01, 2008
BEIJING, Aug. 1 (Xinhuanet) -- A new model construct that follows the simpler physics that dominated the early universe has produced a new supercomputer simulation that offers the most intricate view yet of how the first stars evolved following the Big Bang.
; The simulation reveals how cold clumps of gas eventually became giant star embryos.
"Until you put that physics in the code, you can't evaluate how the first protostars formed," said Lars Hernquist, an astrophysicist at Harvard University whose early-stars model is detailed in this week's issue of the journal Science.
Mysterious "dark matter" provided the first gravitational impetus for hydrogen and helium gas to start clumping together, Hernquist said. The gas began releasing energy as it condensed, forming molecules from atoms, which further cooled the clump and allowed for even greater condensing.
The latest simulation takes this cooling process of "complex radiative transfer" into account, said Nagoya University astrophysicist Naoki Yoshida, who headed up the modeling project.
Eventually gravity could not condense the gas cloud any further, because the densely-packed gas exerted a pressure against further collapse. That equilibrium point marked the beginning of an embryonic star, called a protostar by astronomers.
Simulation runs show that the first protostar likely started with just 1 percent the mass of our sun, but would have swelled to more than 100 solar masses in 10,000 years.
"No simulation has ever gotten to the point of identifying this important stage in the birth of a star," Hernquist noted.
(Agencies)
