The summit of Mauna Kea has been a celestial observatory since ancient times and is one of the best astronomical sites in the world. It is home to many of the world's leading astronomical observatories. The summit is above approximately 40% of Earth's atmosphere and 90% of the water vapor, allowing for exceptionally clear images of the night sky. The peak is well above the inversion layer, allowing up to 300 clear nights per year. At 20 degrees north latitude, much of both the northern and southern skies are visible.
Because Mauna Kea is a shield volcano, road transportation to the summit is relatively easy. The low population density of the island means that there is little man-made light pollution. All of these factors have made Mauna Kea an ideal location for state-of-the-art astronomy.
According to legend, the summit of Mauna Kea is the home of the snow goddess, Poliahu, and many other deities. It is also an important site for prayer, burials, consecration of children, and traditional celestial observation.
Mauna Kea is currently the home of some of the world's largest optical and infrared telescopes, including Gemini, W.M. Keck, Canada-France-Hawai'i, Subaru, NASA, James Clerk Maxwell, United Kingdom Infrared, Very Long Baseline Array, Caltech Submillimeter, University of Hawai`i, and Submillimeter Array.
Several science institutes, in collaboration with the United States Air Force are planning to build Pan-STARRS, a major telescope project, which will be used to near-Earth asteroids. The Thirty Meter Telescope project, the single largest telescope ever built on Earth, is being currently proposed by Caltech, with funding and technology from Intel Corporation.