MRI: Development of a Fiber-Linked Mobile Telescope Facility for the CHARA Array

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Most stars are so distant that even the largest telescopes show them as no more than dots. To see the stars close up would require conventional telescopes that are too large and too expensive to construct. Instead, astronomers use a collection of smaller and distributed telescopes. These work together like a single telescope as large as the separation of the components. One of the best of these is the CHARA Array located at Mount Wilson Observatory in California. The CHARA Array has six telescopes arranged in pairs in fixed locations along three arms. Each telescope sends starlight through long aluminum tubes into a central laboratory for analysis. Each telescope pair is sensitive to a specific size and direction of an object in the sky. Thus, the CHARA Array works best for a size range that is related to the fixed telescope locations. Other sites are needed at larger and smaller separations to study smaller and larger stars. This program will enable these new sites by adding a mobile telescope to the Array. The movable telescope will send starlight through fiber optic cables instead of a bulky tube. This system of seven telescopes will let astronomers make detailed maps of stellar surfaces. This will help place our own Sun within the context of stellar mass, age, and magnetic activity. It will also help train young scientists in the technologies needed to explore outer space.Georgia State University's Center for High Angular Resolution Astronomy (CHARA) operates an optical/near-infrared interferometric array at Mt Wilson Observatory in California. The CHARA Array has six 1 m aperture telescopes in a Y-shaped configuration providing 15 baselines from 34 to 331 meters. With the number and size of its telescopes, the length of its baselines, and the range of wavelength covered by its beam combiners, the CHARA Array is a uniquely powerful facility for milliarcsecond imaging. The goal of this proposal is to develop a new instrument that will expand the spatial dynamic range of the CHARA Array by a factor of ten. The CHARA Michelson Array Pathfinder (CMAP) instrument will be a mobile telescope connected to the Array telescopes through a novel application of fiber optics technology. By placing the mobile telescope close to the pair of telescopes with the smallest baseline, the CMAP instrument will allow us to map the surfaces of large stars, and moving the mobile telescope to distant locations will provide the means to measure details of small stars. This exploration of stars using fiber optics for interferometry will provide the means to map stellar surfaces in unprecedented detail. The CMAP instrument will help train young scientists in the technologies needed for future interferometers on Earth and in space.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.