In 1904 George Ellery Hale, seeking clearer skies than existed near his native Chicago, obtained support from the newly formed Carnegie Institution of Washington to found the Mount Wilson Solar Observatory in the mountains near Pasadena, California. Hale, inventor of the spectroheliograph, discoverer of solar magnetism, and one of the founders of modern astrophysics, was determined to push beyond the descriptive astronomy of earlier generations to understand the internal physics of the Sun and the stars. In pursuit of this goal, stellar telescopes soon followed the initial complement of solar telescopes on Mount Wilson: first the 60-inch, then the 100-inch Hooker telescope, each the largest in the world at the time of its construction.

The Mount Wilson telescopes transformed astronomy and astrophysics. It was with these that Shapley mapped the globular cluster system of the galaxy, Hubble discovered the expanding universe, Baade first recognized the phenomenon of stellar populations, and Adams, Joy, Sandage, and others established the empirical basis for theories of stellar structure and evolution. Striving to push deeper into the universe, in 1928 the Carnegie and Mount Wilson astronomers persuaded the Rockefeller Foundation to fund a 200-inch telescope on Palomar Mountain. Title was given to the California Institute of Technology, which joined with Carnegie to form the Mount Wilson and Palomar Observatories, a partnership that lasted until 1980.

Carnegie astronomers had long wanted an observing station in the Southern Hemisphere that would give them access to the Magellanic Clouds and the center of the Milky Way. The Las Campanas Observatory, located at a superb site high in the southern reaches of Chile's Atacama Desert, was established in 1969 to be home to both 40-inch and 100-inch reflecting telescopes. In 1986, as light pollution encroached from the Los Angeles basin, day-to-day operation of the historical telescopes on Mount Wilson was transferred to the Mount Wilson Institute, and Las Campanas became Carnegie's principal observing site. The newest additions there, twin 6.5-meter reflectors, are remarkable members of the latest generation of giant telescopes.

The main offices of the Carnegie Observatories continue to be located on Santa Barbara Street in Pasadena, California, with about 65 scientific, support, and technical staff in residence. Though a succession of earthquakes felled many of the early buildings, the original 1912 office building still stands, and was recently restored to its early spare elegance. It, and a wing added in the 1960s, house most of the scientific and support staff, as well as an extensive library and photographic plate collection. A new building, completed in 1994, contains a lecture hall, conference room, machine shop, and electronics and instrumentation labs.


Fifty-two hundred miles southeast of Pasadena, about a dozen scientists and administrative personnel work in the offices of the Las Campanas Observatory located in the coastal resort city of La Serena, Chile. The observatory itself is located approximately 100 kilometers north of La Serena, Chile, at an altitude of 2,400 meters, in a region of dark and clear skies and excellent seeing unsurpassed by any site on Earth. The principal telescopes at Las Campanas are the Swope 1-meter telescope, the du Pont 2.5-meter telescope, and the twin 6.5-meter Magellan telescopes. Carnegie operates the latter for a consortium whose other members are Harvard, MIT, and the Universities of Arizona and Michigan.

The Las Campanas telescopes are notable for their exceptionally wide fields. The Swope and the du Pont are Cassegrain equatorial telescopes with a 2-degree field, whereas the Magellan telescopes are alt-azimuth, with both Nasmyth and Cassegrain foci. The Magellan telescopes have a field of 30 arc minutes at the f/11 Nasmyth foci; an f/5 Cassegrain focus with a 1-degree field is planned for the second Magellan telescope. The Las Campanas telescopes are equipped with broad suites of optical and near-infrared cameras and spectrographs. Most of the instruments are designed and built in our shops in Pasadena under the direction of Carnegie astronomers.

Carnegie is a very special place, and the environment of the Observatories reflects the values of an institution dedicated to enabling exceptional scientists to pursue their ideas with complete freedom. Observatories Staff Members and fellows have no other responsibility than to do great science; neither teaching, nor the search for outside funding, nor any other institutional priority need distract them from their own intellectual goals. The institution supports these goals with generous resources. The small scientific staff of about a dozen Staff Members, and an equal number of postdoctoral fellows and associates, have access to time on the institution's three telescopes. The assurance of generous long-term support permits Observatories scientists to pursue long-term projects whose pace is dictated by the pace of discovery itself, rather than by the need to justify the next grant or the next allocation of telescope time. It is this exceptional environment that has enabled the relatively small Carnegie staff to make such disproportionately large contributions to astronomy.

All Staff Members are free to use their time as they see fit, and each uses it differently. Some develop instruments, some are involved in the affairs of the Observatories or the astronomical community, some pursue mostly their own research. Some work alone, but an increasing number are part of broad collaborative projects, both within and beyond the Observatories. The fellowship program is regarded as the final stage in the education of young astronomers. Fellows are encouraged to interact with the senior astronomers, but are free to follow their own paths.

Observatories' scientists interact on a daily basis. Morning tea, held every day in the foyer of the lecture hall, attracts most Staff Members who are in town to talk about every conceivable subject, scientific or otherwise. Most gather again to eat lunch together in our gardens. The Observatories are part of a large and exceptionally lively local astronomical community, which includes scientists from Caltech, JPL, and UCLA. Weekly colloquia at the Observatories and at Caltech attract many from all these institutions.

The Observatories are also active in the Southern California community. There is an annual spring astronomy lecture series, annual open houses, and outreach activities to local schools.

For more about the history of the Carnegie Observatories, see: