Interferometry is a method for combining the light from multiple telescopes to generate an image with exceptionally high spatial resolution. Such acuity cannot be obtained by either telescope alone. This challenging technique can resolve stars outside our solar system, despite their very great distances. Such a feat is impossible with any single telescope, for which even the closest stars are still seen as unresolved points of light. Ordinary interferometry combines the amplitudes of optical telescope signals to form an image. This project utilizes another kind of interferometry that makes use of the quantum nature of light (photons). This quantum approach was first demonstrated in the 1950?s. Kieda and collaborators update this approach by using large, well-separated optical light collectors and fast, modern electronics. They will form images of 35 bright stars over the course of a one-year observing campaign. They will use the VERITAS Observatory and their own dedicated detectors, electronics and data connectivity. This project will serve as a technology pathfinder that may lead to a new regime in ultra-high resolution optical astronomy.
This project will image stars in the UV/Optical bandpass using the method of Hanbury Brown Twiss (HBT) interferometry. This method utilizes the correlation between intensity fluctuations, also called photon bunching, that occurs when different detectors observe the same source. In this method, the intensity correlation time series is the interferometric quantity upon which images are derived. The main advantage of this method is that it is robust to atmospheric turbulence; however, its low inherent sensitivity demands large-area light collectors. It also requires fast time resolution and long integration times. Astronomical observations using HBT were done in the 1960?s and 1970?s during which time the angular diameters of more than 30 stars were measured with a resolution of 1 mas. This method was recently demonstrated on several bright stars with modern detectors and electronics operating in the photon-counting regime. Kieda and collaborators will use the VERITAS gamma-ray observatory telescopes to demonstrate imaging with intensity interferometry. They have validated key technologies for measuring spatial and temporal bunching of blackbody radiation. They have demonstrated the ability to reconstruct images using synthetic data. Their method requires sub-nanosecond synchronization of the data acquisition from multiple detectors spaced at ~100+ meter baselines. This project has the potential to demonstrate a scalable technology and open a wide, unexplored frontier for astronomical, optical imaging with ultra-high resolution.
