Nicholas U. Mayall Telescope, Optical telescope at Kitt Peak National Observatory, Arizona
The Nicholas U. Mayall Telescope is an optical telescope at Kitt Peak National Observatory in Arizona, fitted with a 4-meter primary mirror made of fused quartz. It now houses the Dark Energy Spectroscopic Instrument, a device that uses around 5,000 fiber optic sensors to map the sky.
The telescope opened in 1973 and was at that time the second-largest of its kind in the world. Three years later, observations made with it led to the discovery of methane ice on Pluto, which changed what scientists understood about the outer solar system.
The observatory sits on land belonging to the Tohono O'odham Nation, and this context is present throughout the visit. Signs on the grounds explain the relationship between the research facility and the indigenous community.
The site sits at roughly 6,960 feet (about 2,100 meters) above sea level in a dry mountain area, so bring water and sun protection. Afternoon visits tend to be more comfortable, and guided tours offer the best way to see inside the building.
The building that houses the telescope stands roughly as tall as an 18-story building and can be seen from far across the desert. Its white dome is not just a visual choice: keeping it white prevents the metal from heating up during the day, which would otherwise disturb observations at night.
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