🔭 The Extremely Large Telescope receives its extraordinary dome

On a high desert plateau in Chile, a massive structure is taking shape. The dome of the Extremely Large Telescope (ELT) is being completed to house a giant mirror. This metal enclosure, 80 meters (approx. 262 feet) high, must protect the delicate equipment from the conditions of the Atacama Desert, one of the driest places on the planet.

The design of this dome incorporates innovative technical solutions. Its motorized doors are currently receiving an aluminum coating that limits temperature changes. Special dampers at the base of the structure are designed to withstand seismic shocks, a real risk in this region. The entire upper section will be able to rotate on a concrete base, allowing the telescope to point anywhere in the sky while remaining protected.


Inside this enclosure, five large mirrors will be installed after 2027. The largest of them will measure 39 meters (approx. 128 feet) in diameter, an unprecedented size for an optical instrument. It is this exceptional light-collecting surface that will open new perspectives for observing deep space.

Astronomers hope to perform the first test observations at the beginning of 2029. If everything goes as planned, the real scientific work could begin as early as December 2030. This instrument promises images of a sharpness never before achieved from the ground, far surpassing the capabilities of current telescopes.

The scientific objectives of this project are ambitious. They will include searching for Earth-like planets around other stars and studying very distant celestial objects. The data collected should also provide new information about the formation and evolution of galaxies.

Why observe from a high-altitude desert?

The location of an astronomical observatory is carefully chosen to maximize the quality of observations. High-altitude sites, like the Atacama plateau, place telescopes above a significant part of Earth's atmosphere. This thinner layer of air reduces the disturbances that make stars twinkle.

The atmosphere absorbs and scatters some of the light from celestial bodies, especially in the infrared. Dry, pure air, characteristic of deserts, allows more of this radiation to pass through. This is essential for studying phenomena like star formation, which is often hidden behind clouds of dust but is transparent in infrared.

Another major advantage is atmospheric stability. High-altitude deserts often experience calm winds and clear nights for a large part of the year. This stability limits air turbulence, which blurs images and reduces the sharpness of observations.

Finally, remoteness from major cities significantly limits light pollution. The night sky remains exceptionally dark, allowing the faint glow of the most distant galaxies to be detected without being masked by artificial lights. This is an indispensable condition for exploring the frontiers of the observable Universe.