The Vatican Observatory is one of the oldest astronomical research institutions in the world, with roots tracing back to the Gregorian Calendar reform in the late 16th century and formal establishment as the "Specola Vaticana" in 1891 under Pope Leo XIII. Today it operates out of the papal summer residence at Castel Gandolfo, near Rome, and also runs a modern research facility, the Vatican Advanced Technology Telescope (VATT), atop Mount Graham in Arizona, in partnership with the University of Arizona. Staffed largely by Jesuit priests and brothers who are also professional astronomers, the Observatory studies topics ranging from meteorites and stellar evolution to cosmology, and it maintains that scientific inquiry and religious faith are complementary rather than opposed. It's a distinctive institution: a Catholic Church-run body doing peer-reviewed astrophysics.