10/1/00

UT-Chattanooga Alumnus Makes Major Scientific Contribution

"Astronomy and space hold great fascination for the public partly, I think, hbecause of the grandeur and visual mystery that is the night sky, with the inconceivable distances over which we see the light from the stars overhead."

Those are the words of Dr. Hal McAlister, a 1971 alumnus of UT Chattanooga. He is about to dedicate Georgia State University's Center for High Angular Astronomy (CHARA) Array on Mount Wilson, in the San Gabriel Mountains of California. The event, on October 4, marks the completion of the construction and installation of McAlister's new six-telescope, optical interferometric array.

Speakers at the Oct. 4 dedication ceremony will include Carl Patton, president of Georgia State University; Hon. Joe Frank Harris, former governor of Georgia and a member of the University System of Georgia Board of Regents; James Breckinridge, National Science Foundation; Sidney Wolff, director of the National Optical Astronomy Observatories; Robert Jastrow, director of Mount Wilson Institute; Mercedes Talley, program director of the W.M. Keck Foundation; Terry Ellis, district ranger, Angeles National Forest; and Hal McAlister, director of CHARA. Their comments will be followed by a reception and open house.

The CHARA Array is among the most powerful facilities of its kind in the world, and the only optical array operated by a U.S. university. The Array, constructed in the shadow of the famous 100-inch telescope at the Mount Wilson Observatory, has been under McAlister's care for twenty-three years. To understand the resolution of the Y-shaped configuration of the array, it is the equivalent to the angular diameter of seeing a nickel from a distance of 10,000 miles. (In case you were wondering, the human eye can pick up a nickel at 100 yards.)

How will the Array be used? In astrophysics, it can be used to measure the diameters, distances, masses, and luminosities of stars, in addition to spots and flares on their surfaces. Black hole driven central engines of quasars and active galaxies can also be studied with the Array.

A particularly interesting feature of this high precision system in California is that it can be operated from the Georgia State campus in Atlanta.

McAlister's major at the University was physics/astronomy, and Dr. Karel Hujer was his mentor at the time. He later studied at the University of Virginia, and completed a post-doctoral appointment at Kitt Peak in Arizona.

The native Chattanoogan looks at space exploration as an opportunity to "learn so much about things so remote in the universe by studying light that has traveled for thousands, millions or even billions of years before entering our telescopes."

"We can learn things about the chemistry, age, size, temperature, mass, motion, etc. about stars and galaxies, with no hope of ever reaching these objects, by applying the laws of physics to the light we receive from them. Its the most wonderful detective story there is, unraveling the secrets of the night sky," McAlister said.

McAlister is married to Susan Johnson McAlister, also a UTC graduate (English/Secondary Education '72). The pair met at what was then UC during the summer after their freshman year.

For more background information about the CHARA Array, go to wwww.chara.gsu.edu/CHARA/array.html

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