Portable Multi-Channel Intensity Interferometer

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In the continual effort to obtain better images of objects in the universe, the emphasis has generally been centered on orbiting observatories or ever-larger ground-based facilities with laser correction of atmospheric turbulence. Both are expensive endeavors with physical limitations. A quite different approach, intensity interferometry, has a significant history in radio astronomy, but was last seriously used for the optical regime in the 1970's using the simple detectors available at the time. Dr. E. Horch of Southern Connecticut State University (SCSU) has recognized that today's very sensitive, extremely fast solid-state detectors motivates that the technique be re-examined, as it would offer the possibility of obtaining separations of orbiting binary stars, stellar diameters, and even complete stellar images using a small array of inexpensive, modest-sized telescopes and commercially available instrumentation. Indeed, the SCSU project is being promoted as an activity well-suited to student involvement at a small undergraduate university.Intensity interferometry for astronomy utilizes the Bose-Einstein correlation of bosons (and therefore photons) to provide information on the angular size of the radiating source. For telescopes with somewhat less than 1-m aperture distributed over the SCSU campus, Dr. Horch predicts that an angular resolution of 0.1 milliarcseconds can be achieved down to a visual magnitude of ~3.5, allowing detailed inspection of about 200 stars. For comparison, the Sun moved to a distance that yields this apparent magnitude would have an angular diameter of 2 milliarcseconds. Moreover, the effect can be monitored in several wavebands simultaneously through the use of Single Photon Avalanche Diode (SPAD) arrays that have quantum efficiencies near 0.5 and time response of ~0.1 nanoseconds, and the data recorded using GPS technology.Funding for the development of a modern two-telescope prototype of an intensity interferometer array for the optical is being provided by NSF's Division of Astronomical Sciences through its participation in the Major Research Instrumentation program.