What is CHARA?
The flagship project of Georgia State University's Center for High Angular Resolution Astronomy (CHARA) is its optical interferometric array of six telescopes located on Mount Wilson, California. Each telescope of the CHARA Array has a light-collecting mirror 1-meter in diameter. The telescopes are dispersed over the mountain to provide a two-dimensional layout that provides the resolving capability (but not the light collecting ability!) of a single telescope with a diameter of 330 meters (one fifth of a mile)! Light from the individual telescopes is transported through vacuum tubes to a central Beam Synthesis Facility in which the six beams are combined together. When the paths of the individual beams are matched to an accuracy of less than one micron, after the light traverses distances of hundreds of meters, the Array then acts like a single coherent telescope for the purposes of achieving exceptionally high angular resolution. The Array is capable of resolving details as small as 200 micro-arcseconds, equivalent to the angular size of a nickel seen from a distance of 10,000 miles. In terms of the number and size of its individual telescopes, its ability to operate at visible and near infrared wavelengths, and its longest baselines of 330 meters, the CHARA Array is arguably the most powerful instrument of its kind in the world.
The Array is applicable to problems in almost all areas of contemporary astronomy. It is particularly suited to stellar astrophysics where it is be used to measure the diameters and temperatures of stars, image features such as spots and flares on their surfaces, and map the orbits of close binary companions. Other projects range from detecting other planetary systems, imaging stars in process of formation, and studies of bright transient phenomena like novae.