2007 ASP Annual Award Recipients
and Eric Muhlmann Award
Harold A. McAlister
Georgia State University & the CHARA Array Project
Although optical astronomers operate at wavelengths four to five orders of magnitude shorter than those used by radio astronomers, and although the diameters of optical telescopes are approaching those of some radio telescopes, the highest resolution available to astronomers has generally been in the radio regime. The reason is simple: radio astronomers can use the technique of interferometry, combining signals received from several reflectors to produce images with a resolution set by the size of the array of reflectors, not the aperture of an individual one.
Optical astronomers are making rapid strides in introducing interferometric techniques to the near infrared and optical. A leader in this effort is Harold McAlister, this year's recipient of the Maria and Eric Muhlmann Award presented each year for "significant observational results made possible by innovative advances in astronomical instrumentation." Harold McAlister led the Center for High Angular Resolution Astronomy (CHARA) team that designed, built and is now operating an array of 1-meter telescopes that form the most powerful optical interferometer now available. This has helped bring milli-arcsec resolution to optical astronomy, rivaling the best resolutions obtainable at radio wavelengths. The CHARA array has directly measured the diameters not just of giant and supergiant stars but also of much smaller M dwarfs. It has also enabled astronomers to measures the shapes of both rotationally distorted stars and close binary systems, leading to accurate stellar masses. These same interferometric techniques will form the basis of advanced, satellite missions to study planets orbiting other stars.