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Posted 10-2-98
Some people build model cars and airplanes. Case Western Reserve University's Christopher Mihos designs computer models of colliding galaxies and black holes.
His models answer important questions about galactic evolution, the study of galaxy formation over time.
What may look like a fuzzy patch of light in the night sky actually can be a blazing and dynamic inferno of millions of new star formations from two colliding galaxies. The impact shocks and squeezes dust and gases into the center of a newly formed galaxy.
This has happened to M87, the brightest star in the constellation Virgo and one that particularly interests the assistant professor from the Department of Astronomy.
From information provided by a variety of high powered telescopes, astronomers have gleaned that the universe is more dynamic than once thought. Just 30 years ago, astronomers thought galaxies were "island universes," Mihos said.
They know differently now. New galaxies and stars continue to form as galactic paths cross in space. Spiral galaxies, like the Milky Way, dance around each other and then turn back as the force of gravity pulls them together to create an oblong or elliptical galaxy.
A small galaxy called Sagittarius Dwarf is falling into the far edge of our Frisbee-shaped Milky Way. Much of the action cannot be seen by normal eyesight, since the collision is masked by the dense disk of stars orbiting around the center of the Milky Way.
The Milky Way is easily absorbing Sagittarius Dwarf, but galactic fireworks will erupt millions of years from now when Andromeda and the Milky Way meet, and the two masses of almost equal size create a tug-of-war in space.
"Some of the brightest objects in the universe seem to be the end stages of mergers," explained Mihos. It's the last glow of a brilliant starburst before all gas from the two galaxies is used up. The galaxy's center then becomes a round fuzzy blob without much star emission, according to Mihos. It may also contain a black hole, swallowed up like a swirl of water draining from a bath tub.
Mihos joined the faculty in the spring semester. He came to CWRU from Johns Hopkins University, where he was a Hubble Fellow. Interested in stars from an early age, he pursued astronomy at the California Institute of Technology (Caltech), where he earned his Ph.D.
He continues to research galactic evolution with a three-year, $250,000 grant from NASA. He is part of a collaboration with Steinn Sigurdsson from Penn State University, Lars Hernquist of the University of California at Santa Cruz, and Colin Norman of Johns Hopkins University. The group generates computer models of the effects of black holes on galactic formation in a project called, "Evolution of Galaxies, Harboring Massive Black Holes."
"With computer models, we can follow what happens to the stars and the gas in these galaxies," said Mihos.
This whole process takes billions of years. Computer modeling enables Mihos and other theoretical astronomers to take all the different snapshots of various galactic collision from telescope astronomers and use that information to show how galaxies form and evolve.
"Models help tie together the qualitative arguments that can be made about evolution with some quantitative footings," added Mihos.
Computer modeling for astronomers had its inception in the late 1960s. High-powered computers have allowed astronomers to search for more complicated answers to questions about galaxies, such as Mihos' new project on black holes and what happens when black holes from two galaxies merge.
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