Georgia State University
Atlanta, Georgia


Dr. Hal McAlister

Director, Center for High Angular Resolution Astronomy

Georgia State University


Kim MacQueen

University Relations


FOR IMMEDIATE RELEASE: November 24, 1999


Atlanta — Astronomers at Georgia State University have obtained the first results from a new telescope array on
Mount Wilson, California. The “CHARA Array,” designed and operated by the University’s Center for High Angular
Resolution Astronomy (CHARA), will incorporate six telescopes distributed over the grounds of the historic Mount
Wilson Observatory. Two of these telescopes are presently installed and the remaining four will be put in place this
winter. Each of the new telescopes has a light-collecting mirror 1 meter in diameter that relays starlight through
vacuum pipes to a central beam combination facility. The central facility houses optics that combine the light to an
accuracy of one-millionth inch using the techniques of optical interferometry, enabling the array of six telescopes to
work together as a single telescope 400 meters in diameter. This will allow the CHARA Array to see detail in
astronomical objects as small as one ten-millionth of a degree in angular extent. This

Last night, CHARA astronomers successfully combined light from the two telescopes in the first demonstration that
the Array will function as designed. The pair of telescopes was pointed at the bright stars gamma Eridani, alpha Canis
Majoris (also known as Sirius) and alpha Hydrae. At the point of combination of the light, more than 200 meters
from the collecting telescopes, the astronomers saw and recorded interference fringes rushing across the screen of
an oscilloscope. These fringes are the direct evidence that all the necessary optical, mechanical, and electronic
subsystems as well as the computer software that controls them, were functioning correctly.

Dr. Harold McAlister, CHARA Director, said, “This is the major milestone we’ve been working towards since ground
was broken in 1996. We now have evidence that the Array will live up to our expectations.” These expectations
include the imaging of surfaces of stars like the sun, the measurements of orbital motions in binary systems of stars
that orbit each other in just a few days, the detection of planets in multiple star systems, and the detection of disks of
pre-planetary material around newly forming stars. “We’re elated,” McAlister said, “and we look forward to
obtaining new scientific results as we finish all the remaining work needed to combine light from all six telescopes.
We have a lot yet to do, but at least we can prove that the Array will work.”

When fully operational in early 2001, the CHARA Array will be among the world’s most powerful instruments for
measuring details of the surfaces of stars and their nearby environments. Funding for the $13.5-million facility has
been provided by the National Science Foundation, Georgia State University, the W.M. Keck Foundation, and the David
and Lucile Packard Foundation.

Visit CHARA’s website at