What is CHARA ?

Photo courtesy Eric Simison, Sea West Enterprises

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 a fifth of a mile in diameter. Light from the individual telescopes is conveyed 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.