From the summit of Hawaii’s dormant Mauna Kea volcano, astronomers at the W. M. Keck Observatory probe the local and distant Universe with unprecedented power and precision.
Their instruments are the twin Keck telescopes—the world’s largest optical and infrared telescopes. Each telescope stands eight stories tall, weighs 300 tons and operates with nanometer precision. The telescopes’ primary mirrors are 10 meters in diameter and are each composed of 36 hexagonal segments that work in concert as a single piece of reflective glass.
In the middle of the Pacific Ocean, Hawai’i Island is surrounded by thousands of miles of thermally stable seas. The 13,796-foot Mauna Kea summit has no nearby mountain ranges to roil the upper atmosphere. Few city lights pollute Hawaiian night skies, and for most of the year, the atmosphere above Mauna Kea is clear, calm and dry.
Because of the large size of the 10-meter primary mirrors, the Keck telescopes offer the greatest potential sensitivity and clarity available in astronomy. Their performance, and the performance of all ground-based telescopes, is limited by the turbulence of the Earth’s atmosphere, which distorts astronomical images. Astronomers have recently overcome the effect of atmospheric blurring using an established and fundamental technique called adaptive optics (AO).
AO corrects for the image distortions by measuring and then correcting for the atmospheric turbulence using a deformable mirror that changes shape 2,000 times per second. In 1999, the Keck II telescope became the first large telescope worldwide to develop and install an AO system. The results provided a tenfold improvement in image clarity compared to what was previously possible with Keck and other large, ground-based telescopes.
Initially adaptive optics relied on the light of a star that was both bright and close to the target celestial object. But there are only enough bright stars to allow adaptive optics correction in about one percent of the sky. In response, astronomers developed laser guide star adaptive optics using a special-purpose laser to excite sodium atoms that sit in an atmospheric layer 90 kilometers above Earth. Exciting the atoms in the sodium layers creates an artificial “star” for measuring atmospheric distortions and allows adaptive optics to produce sharp images of celestial objects positioned nearly anywhere in the sky.
In 2004, Keck Observatory deployed the first laser guide star adaptive optics system on a large telescope. The laser guide star AO now routinely produces images with greater crispness and detail than those resulting from the Hubble Space Telescope.
The W. M. Keck Foundation funded both the original Keck I telescope and six years later, its twin, Keck II. The project was managed by the University of California and the California Institute of Technology. The Keck I telescope began science observations in May 1993; Keck II saw first light in October 1996. In 1996, the National Aeronautics and Space Administration (NASA) joined as a one-sixth partner in the Observatory.
Today Keck Observatory is a 501(c)3 supported by both public funding sources and private philanthropy. The organization is governed by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California, with liaisons from NASA and the Keck Foundation
The Observatory endorses and supports the Astro2010 Decadal Survey process. Its senior staff members and Science Steering Committee, along with colleagues at WMKO’s partner institutions, have provided community input through the following contributions: