First Starlight Fringes at the CHARA
Array
First starlight fringes were observed with the CHARA Array at about 1:00 am local time on Tuesday, 23 November 1999. Fringes were obtained using K-band (2.2 microns) on Gamma Eridani, Alpha CMa, and Alpha Hydrae using a baseline of 34 meters. A linear sweep was used and fringes were found within 4 cm of where the astrometric model predicted. Fringes for Sirius (Alpha CMa) are shown above.
Also see the brief news report in Sky and Telescope's Reports on Astronomy and Space Science, and the New York Times article of November 30, 1999 titled ``6-Eyed Creature to Watch Sky on Famed Peak."
The ``6-Eyed Creature" is of course the interferometer and not Nils, Steve, Judit, Theo, Laszlo, and Hal, pictured below.
Press Release
Tuesday, November 23, 1999
GEORGIA STATE'S NEW TELESCOPE ARRAY ACHIEVES FIRST RESULTS
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 is equivalent to structures the size of a personal computer on the moon or a football field on Mars.
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.
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Courtesy of Theo ten Brummelaar and Hal McAlister.