Planets May Form Faster than Scientists Thought
Simulations at Pittsburgh Supercomputing Center show that planets can form in hundreds of years.
PITTSBURGH, December 11, 2002 Taking advantage of the computing capability of LeMieux, the Pittsburgh Supercomputing Center's terascale system, scientists have determined that large, Jupiter-like planets similar to those observed outside Earth's solar system can form in dramatically shorter periods of time than previously thought.
The findings, published in SCIENCE (Nov. 29), challenge accepted thinking that it takes millions of years for such planets to form from the pancake-shaped nebula of gas and dust swirling around young stars.
"We used a new model of planet formation," said University of Washington astrophysicist Thomas Quinn, who led the research team, "that couldn't adequately be tested without this kind of computing power, and we found that these giant planets can form in hundreds of years, rather than the millions that the standard model predicts."
Using LeMieux, the most powerful system in the United States committed to public research, the researchers carried out a series of planet formation simulations. Because of LeMieux, the researchers were able to include roughly ten times more detail than previous similar work, and this increased resolution led directly to the new findings.
Nearly 100 extrasolar planets have been detected within the past decade, with masses that range from roughly the size of Jupiter to ten times larger. These discoveries prompted thinking about how large planets, similar to Jupiter and Saturn, form. Called gas giant planets, these planets have most of their mass in a gaseous envelope that surrounds the solid core.
The standard model holds that a core of solid matter congeals from the swirling disk called a protoplanetary disk around young stars, a process thought to take a million years or so, with another million to ten million years to accumulate the gaseous envelope. The problem with this model, however, is that if the formation process takes too long, nearby stars will, in effect, boil off the gas envelope. "If a gas giant planet can't form quickly," said Quinn, "it probably won't form at all."
An alternative model holds that giant planets form directly from instabilities in the protoplanetary gas, without the need for a solid-matter core. Until the recent simulations, this model hadn't produced convincing results. "The main criticism," said Quinn, "was that this model wasn't ready. Nobody was making predictions with it. But that's because they didn't have enough computational horsepower."
The recent simulations using 30,000 processor hours on LeMieux produced a distribution of masses and orbits comparable to observed extrasolar planets. According to the astronomical findings since the mid-1990s, these gas giant planets appear to be fairly common. "If these planets can't form quickly," says Quinn, "they should be a relatively rare phenomenon, and if they form according to this mechanism they should be relatively common."
Authors of the research, besides Quinn, are Lucio Mayer, a former University of Washington post-doctoral researcher who recently joined the University of Zurich, James Wadsley of McMaster University, Ontario, Canada and Joachim Stadel at the University of Victoria, British Columbia, Canada.
Established with an August 2000 grant from the National Science Foundation, LeMieux comprises over 3,000 Compaq Alpha EV68 processors, providing over six teraflops (six trillion calculations a second) of computational capability to U.S. engineers and scientists.
The Pittsburgh Supercomputing Center is a joint effort of Carnegie Mellon University and the University of Pittsburgh together with the Westinghouse Electric Company. It was established in 1986 and is supported by several federal agencies, the Commonwealth of Pennsylvania and private industry.
© Pittsburgh Supercomputing Center.