Within the diffuse medium of gas and dust that floats between the stars, scientists have discovered objects spanning tens of light-years in diameter that are so dense you can't see the stars behind them. These seemingly solid masses, called "giant molecular clouds," or GMCs, are on the order of 10,000 to 1,000,000 times more massive than our Sun, and the temperatures within them hover around minus 473 degrees Fahrenheit.
These giant clouds are formed from a poorly understood and complex interaction of supersonic stellar winds generating extreme turbulence, similar to the violently churning eddies of water so familiar to whitewater rafters, gravitational forces, physical interactions between the dust particles themselves, and the magnetic effects created by gaseous ions within the giant clouds.
The real surprise to scientists, though, has been the discovery of a variety of complex molecules in the depths of these coldest, darkest regions of space, some of which form the basis of life. "It's a bit like opening up your freezer and finding the uncooked pizza you put in a week ago burnt to a crisp," said Dr. Robert Fisher, an assistant physics professor at the University of Massachusetts Dartmouth.
By developing a computer model of this dynamic environment, Fisher hopes to provide a window into how these molecules are formed, as well as the process of star formation itself. These computer simulations can then be compared with the actual data to be gathered on these clouds by a new generation of dish radio antennas currently being built high in the clear air of the Andes of Chile, the Atacama Large Millimeter/submillimeter Array, or ALMA. These antennae have been specifically designed to provide the high-quality astrochemical observations that currently elude scientists probing these giant clouds.
Physicists disagree, however, as to whether turbulence or magnetism is the dominant driving force. Fisher hopes to resolve the issue by creating a simplified computer model which takes both mechanisms into account. Developing such a model, says Fisher, requires choosing a simple enough problem without complicating factors, capturing what he calls "the essential physics" by understanding what sets up the initial conditions.
If the resulting model fits with the observed behavior of the giant clouds, scientists use the observations to further refine the model, continually comparing it against observations, thereby creating a powerful tool for further understanding the inner dynamics of these volatile regions of our universe.
An early fascination with physics, astronomy, and computers led Fisher into astrophysics, the branch of physics dealing with the physical properties of galaxies, planets, stars, and the diffuse medium of gas and dust between the stars. He was part of a team of scientists at the University of Chicago that used what an article in New Scientist dubbed "extreme computing," the equivalent of 7 years' worth of processing on an ordinary PC, to simulate "the dramatic death of a white dwarf star in a violent explosion" in 2007. The model was considered controversial, however, because it couldn't be replicated by other teams, a necessary prerequisite to establishing the validity of the model.
Using all the tools of the physics trade, from Newtonian mechanics and thermodynamics to atomic physics and relativity, astrophysicists probe the universe for clues into its origins and evolution: How do stars form? What is "dark matter"? What's driving the apparent expansion of the universe? How do complex molecules form within giant clouds? By combining theory with detailed observations and building computer simulations of these processes, one variable at a time, astrophysicists hope to answer some of these perplexing questions that seem to fly in the face of our everyday common sense.
"What happens on the big scale is always connected with what happens on the small scale," says Fisher. He hopes that by modeling these giant clouds on a small scale, he will be able to contribute to our understanding of these clouds on a big scale and eventually solve one more piece of the fascinating puzzle that is our universe.
Kathy Kieva - With a life-long fascination with science and a love of the written word, it has been - and continues to be - a joy to combine the two: as ...
