Our Origins

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 San Gabriel mountains near Pasadena, California. Hale 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 solar telescopes on Mount Wilson, each the largest in the world at the time of its construction. First light on the 60-inch was in 1908 and first light on the 100-inch Hooker telescope was in 1917.

Observatory dome of the Hooker 100-inch telescope, Mount Wilson Observatory.

Mount Wilson and Palomar

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). First light on the Palomar Hale telescope was in 1949.

Las Campanas Observatory.

Las Campanas Observatory

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. So while construction of the Palomar Hale telescope was still ongoing, The Las Campanas Observatory–located at a superb site high in the southern reaches of Chile's Atacama Desert–was established in 1969. First light on the 40-inch Swope telescope was in 1971 and it was soon followed by first light on the 100-inch du Pont telescope in 1977. 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, the twin 6.5-meter Baade and Clay reflectors, saw first light in 2000 and 2002, respectively. In 2015, construction at Las Campanas started for the Giant Magellan Telescope (GMT), Carnegie’s latest contribution to cutting-edge giant telescopes. First light for GMT is expected in 2029.

Carnegie Observatories Santa Barbara Street campus.

Santa Barbara Street

The main offices of the Carnegie Observatories continue to be located on Santa Barbara Street in Pasadena, California. Though a succession of earthquakes in the 1980s felled many of the early buildings, such as the original machine and optical shops, the original 1912 office building still stands because it was one of the first buildings to have steel rebar included in its thick cement walls and the basement levels. This office building, designed by Myron Hunt, was intended to be fireproof because a fire at Harvard College in 1764 had destroyed a massive amount of the College’s observing equipment and records. The Hunt building 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. The most recent buildings, completed in 1994, contain a lecture hall, conference room, machine shop, and electronics and instrumentation labs. In 2020, one of the campus garages was converted into the state-of-the-art VizLab, an immersive visualization display system with 35 2D- and 3D-capable flat panels in the shape of a cresting wave, that enables the visualization of data so that it can interrogated and interpreted in ways that help astronomers discover how our universe works.



First meeting of the Carnegie Institution of Washington’s Board of Trustees, January 29, 1902

Andrew Carnegie establishes the Carnegie Institution for Science, then called the Carnegie Institution of Washington, with a $10 million gift.

	 Andrew Carnegie and George Ellery Hale in front of the 60-inch telescope, Mount Wilson Observatory.

Carnegie funds George Ellery Hale's proposal to build the Mount Wilson Solar Observatories in the mountains overlooking Pasadena.

George Ellery Hale at the spectrograph of the 60-foot solar tower telescope, Mount Wilson Observatory.

Aided by a spectroheliograph of his own design, George Ellery Hale discovers that sunspots are intense magnetic fields. This discovery was the first detection of a magnetic field beyond that of Earth.

Blueprint for the 60–inch telescope and dome, Mount Wilson Observatory.

The 60-inch reflecting telescope at Mount Wilson Observatory sees first light.

60–inch reflecting telescope, Mount Wilson Observatory.

The 100-inch Hooker telescope at Mount Wilson Observatory sees first light. The Hooker telescope was the largest in the world from 1917-1949 and enabled discoveries that transformed our understanding of the scale and nature of the universe.

60-inch reflecting telescope, Mount Wilson Observatory.

Harlow Shapley maps the globular cluster system of the galaxy and finds its center, toppling the almost 400-year-old Copernican model of a Sun-centered universe.

VAR plate taken by Edwin Hubble on the 100–inch telescope at Mount Wilson Observatory.

Edwin Hubble discovers the first Cepheid variable star in M31 proving that the universe exists beyond our Milky Way galaxy.

Edwin Powell Hubble seated at the 100-inch reflecting telescope, Mount Wilson Observatory.

Edwin Hubble discovers that the universe is expanding.

Edwin Powell Hubble, Albert Einstein and five others gathered at the Hale Library, Pasadena.

Meeting with physicists and astronomers in the Carnegie Observatories library, Albert Einstein announced that although he'd been famously resistant to Edwin Hubble's assertion that the universe was expanding, the visit had changed his mind.

The 200-inch Hale telescope.

The 200-inch Hale telescope on Palomar see first light, replacing the 100-inch Hooker Telescope as the largest in the world. The joint Caltech-Carnegie Mount Wilson and Palomar Observatories partnership lasted until 1980.

Walter Baade.

Walter Baade recognizes the phenomenon of stellar populations and starts a revolution that led to our understanding of the nature of stars, their life cycles, and the evolution of the Milky Way Galaxy.

Las Campanas Observatory.

Carnegie begins construction of Las Campanas Observatory in Chile's Atacama Desert, a site chosen for its ink-dark skies and dry stable air, which provide ideal observing conditions for the some of the best "seeing" in the world.

Swope telescope.

The 40-inch Swope Telescope at Las Campanas Observatory sees first light.

Du Pont Telescope.

The 100-inch du Pont Telescope at Las Campanas Observatory sees first light.

Allan Sandage.

Carnegie's Allan Sandage is awarded the Crafoord Prize for his "contributions to the study of galaxies, their populations of stars, clusters and nebulae, their evolution, the velocity-distance relation (or Hubble relation), and its evolution with time."

Night sky.

Mark Phillips establishes the relationship-informally named after him-that allows Type la supernovae to be used as standard candles for measuring the expansion rate of the universe.

Twin Magellan Telescopes.

The 6.5-meter Magellan Baade telescope at Las Campanas Observatory sees first light. Two years later the 6.5-meter Magellan Clay telescope would see first light.

Wendy Freedman.

Carnegie astronomy Wendy Freedman and team publish a new measurement of the expansion rate of the universe, or Hubble Constant, using Hubble Space Telescope observations to reach more distant Cepheid variables.

Giant Magellan Telescope.

Scientists and engineers from Carnegie, Harvard University, Smithsonian Institution, and the University of Arizona develop the conceptual design for the Giant Magellan Telescope, which will be built at Carnegie's Las Campanas Observatory.

The first blast at the Giant Magellan Telescope site.

Site preparation for the Giant Magellan Telescope begins at Las Campanas Observatory, with the first of 70 controlled blasts to level the highest mountaintop.

Artist's conception of neutron stars colliding, by Robin Dienel, courtesy of Carnegie Institution for Science

Using Carnegie's Swope telescope, a team of Carnegie astronomers provides the first-ever glimpse of two neutron stars colliding.

A person stands in front of an immersive visualization display system with 35 2D- and 3D-capable flat panels in the shape of a cresting wave

The Carnegie Theoretical Astrophysics Center is founded and construction is complete on its flagship initiative, the 3D virtual reality enabled visualization lab or Vizlab.

Rendering of the Magellan Infrared Multi-object Spectrograph (MIRMOS).

Carnegie astronomer-led teams are awarded funding from the Heising-Simons Foundation for MIRMOS and MagNIFIES, two groundbreaking instruments that will help reveal galaxy evolution and exoplanet formation and atmospheric makeup in unprecedented detail.

Rendering of the Giant Magellan Telescope (GMT) at night showing the design of the telescope, enclosure and summit.

The National Academies names the Giant Magellan Telescope and U.S. Extremely Large Telescope program a top strategic priority.

Plate Vault

Explore the Plate Archives

In the basement of the Observatories’ Santa Barbara Street office is the Plate Vault, home to the second largest collection of astronomical glass plates in the United States.

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Scientist working in the lab.

A Legacy of Discovery

For more than a century, Carnegie has empowered visionary investigators to demonstrate intellectual courage, challenge conventional ideas, and transform the world.

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