Observatories Around the World

An observatory is any facility designed to collect and analyze light or other signals from astronomical objects. The oldest continuously operating scientific observatory, the Paris Observatory, was founded in 1667 under King Louis XIV of France, and the Royal Observatory at Greenwich followed in 1675 under King Charles II of England. For most of the subsequent three centuries, observational astronomy meant visible-light observations from ground-based telescopes placed on hills, estates, or university grounds. The twentieth century transformed that tradition. Advances in mirror casting, active optics, adaptive optics, radio electronics, and space flight opened entirely new windows on the universe, and purpose-built facilities were placed on remote mountain peaks, in deep caverns, beneath Antarctic ice, and in Sun-Earth Lagrange orbits where conditions favor the required observations.

Modern observatories are classified first by the wavelength band they observe and then by their location. Optical and near-infrared observatories are generally ground-based and are placed at high altitude in dry, dark, atmospherically stable locations. The four premier optical sites in operation are Mauna Kea in Hawaii, Cerro Paranal and Cerro Tololo in the Chilean Atacama, the Canary Islands peak of Roque de los Muchachos on La Palma, and the desert mountaintops of the American Southwest. Radio observatories require radio-quiet zones but can operate at lower elevations. X-ray and gamma-ray astronomy, whose photons cannot penetrate the atmosphere, is carried out almost entirely from space. A new generation of multi-messenger observatories uses detectors that are sensitive to gravitational waves or high-energy neutrinos rather than electromagnetic radiation.

Observatories are operated by national agencies, multinational consortia, and large university partnerships. In the United States, ground-based astronomy is coordinated primarily through the National Science Foundation and the NOIRLab system. Space-based programs are led by the National Aeronautics and Space Administration (NASA) and, in Europe, by the European Space Agency (ESA). The European Southern Observatory (ESO), founded in 1962, operates the premier ground-based facilities of the southern hemisphere and is jointly supported by sixteen member states. Japan's National Astronomical Observatory (NAOJ), the CSIRO in Australia, the Chinese Academy of Sciences, and other national bodies operate complementary facilities. A growing number of major projects, including the Atacama Large Millimeter Array and the Square Kilometre Array, are organized as transnational scientific partnerships.