CHARA

CHARA

The Center for High Angular Resolution Astronomy Array is an optical/infrared interferometric observatory located on Mount Wilson, California, operated by Georgia State University with contributions from institutions such as the California Institute of Technology, the University of Michigan, the University of Cambridge, and the Naval Research Laboratory. It provides sub-milliarcsecond angular resolution used in studies that involve targets including stars, exoplanets, active galactic nuclei, and interacting binaries. Instruments and baselines are configured to enable imaging and precision measurements that complement facilities like the Very Large Array, Keck Observatory, and the Hubble Space Telescope.

Overview

CHARA is an interferometric telescope array composed of six fixed-aperture telescopes whose light is combined in long baseline beam paths to achieve high angular resolution comparable to very large telescopes. The array serves communities associated with institutions such as Georgia State University, the California Institute of Technology, the University of Michigan, the University of Cambridge, the Naval Research Laboratory, the Max Planck Institute for Astronomy, the University of Amsterdam, and the European Southern Observatory through collaborative projects. CHARA complements instruments and missions including the Keck Interferometer, the Very Large Telescope Interferometer, the Hubble Space Telescope, the James Webb Space Telescope, the Atacama Large Millimeter/submillimeter Array, and the Submillimeter Array by providing optical/near-infrared spatial detail. Typical science programs connect to targets and programs involving stars like Betelgeuse, Vega, Altair, Fomalhaut, and rapidly rotating and evolved stars studied in contexts similar to those at the Mount Wilson Observatory and Palomar Observatory.

History and Development

The array was conceived and constructed in the 1990s with funding and scientific guidance from agencies and institutions including the National Science Foundation, Georgia State University, the California Institute of Technology, and partner observatories such as Mount Wilson Observatory and Palomar Observatory. Early development drew on technical heritage from projects like the Michelson stellar interferometer, the Narrabri Stellar Intensity Interferometer, the Navy Prototype Optical Interferometer, and the Cambridge Optical Aperture Synthesis Telescope. Milestones in the array's commissioning involved technical contributions and collaborations with groups from the University of Michigan, the University of Cambridge, the Max Planck Institute for Radio Astronomy, the Naval Research Laboratory, the Space Telescope Science Institute, and NASA research programs. Subsequent upgrades integrated instrumentation advancements influenced by work at the European Southern Observatory, the Max Planck Institute for Astronomy, the Leiden Observatory, the University of Amsterdam, and the University of Exeter.

Array Design and Instrumentation

The six-telescope array employs siderostats and evacuated beam tubes to route light to a central beam combining facility, enabling baselines up to several hundred meters and angular resolution rivaling large single-aperture telescopes. Beam combiners developed for the facility draw on concepts and technologies used at the Very Large Telescope Interferometer, the Keck Interferometer, and the Navy Precision Optical Interferometer, with detectors and cryogenic systems influenced by instrumentation at the European Southern Observatory, the Max Planck Institute, the Jet Propulsion Laboratory, and the Space Telescope Science Institute. Adaptive optics and fringe tracking modules take advantage of developments from the Palomar Observatory, the Lick Observatory, the University of Hawaii, the Carnegie Institution for Science, and the California Institute of Technology. Data reduction pipelines and image reconstruction algorithms are related to methods used by teams at the Harvard-Smithsonian Center for Astrophysics, the University of Cambridge, the Max Planck Institute for Radio Astronomy, the University of Michigan, and the University of California, Berkeley.

Scientific Research and Discoveries

Research produced by the observatory spans stellar astrophysics, binary star characterization, rotating star imaging, stellar surface mapping, circumstellar disk studies, and exoplanet host characterization. Scientific programs have observed resolved surfaces and limb darkening on stars such as Altair, Vega, Regulus, Achernar, and Betelgeuse, and resolved binary orbits used to refine masses for systems observed also by missions like Gaia, Hipparcos, and Kepler. Studies of pre-main-sequence stars and Herbig Ae/Be systems connect to research at the European Southern Observatory, the Atacama Large Millimeter/submillimeter Array, the Submillimeter Array, and the Keck Observatory. Measurements of angular diameters and effective temperatures inform stellar evolution models from groups at the University of Cambridge, the Max Planck Institute for Astronomy, the University of Michigan, and Princeton University. Collaborative work with teams from NASA, the Space Telescope Science Institute, the Jet Propulsion Laboratory, the California Institute of Technology, and the Harvard-Smithsonian Center for Astrophysics has advanced understanding of active galactic nuclei, interacting binaries like Algol-type systems, and rapidly rotating stars akin to those studied in the context of the Royal Greenwich Observatory and Mount Wilson Observatory.

Operations and Collaborations

Operations are managed by Georgia State University with technical partnerships and observing time exchanged among institutions such as the California Institute of Technology, the University of Michigan, the University of Cambridge, the Naval Research Laboratory, the Max Planck Institute for Astronomy, the Leiden Observatory, and the University of Amsterdam. The facility interfaces with international networks and projects including the European Southern Observatory, the Very Large Telescope Interferometer, the Keck Interferometer, the Atacama Large Millimeter/submillimeter Array, the Hubble Space Telescope, the James Webb Space Telescope, and the Square Kilometre Array pathfinder teams through data sharing and coordinated campaigns. Educational and outreach collaborations involve organizations like the Space Telescope Science Institute, the American Astronomical Society, the International Astronomical Union, the National Science Foundation, and local institutions including Mount Wilson Observatory and Caltech. Future plans and upgrade paths consider synergies with projects at the Max Planck Institute for Radio Astronomy, the University of Cambridge, the Jet Propulsion Laboratory, NASA astrophysics programs, and international partners such as the European Southern Observatory and the Leiden Observatory.

Category:Observatories