Exciting news from the Atacama Desert in Chile!

The frame of the protective dome for the world’s largest telescope, the European Southern Observatory's Extremely Large Telescope (ELT), has officially been completed, marking a significant milestone in the observatory’s ambitious construction project.

A Revolutionary Instrument

Situated on the towering Cerro Armazones mountain, the ELT is set to revolutionize our understanding of the universe. Expected to achieve its “first light” by 2028, this unprecedented telescope will be capable of capturing visible and infrared light, paving the way for groundbreaking discoveries about terrestrial exoplanets and their atmospheres, as well as advancing our understanding of cosmic expansion.

Impressive Scale of the Dome

Recent photos reveal the impressive scale of the dome, which measures an astonishing 305 feet (93 meters) in diameter—roughly the size of a football field—and reaches a height of 263 feet (80 meters). Currently, work is underway to add aluminum plates to envelop the dome, shielding the sophisticated telescope from the harsh climatic conditions of the Atacama Desert, notorious for its extreme temperatures and aridity.

Innovative Features

What’s more, the dome will feature large sliding doors, designed to remain closed during the harsh daylight hours and open at night, allowing astronomers to survey the starry skies with optimal efficiency. As of January 2025, cranes are actively installing the outer aluminum cladding, showcasing the rapid progress being made.

Groundbreaking Mirror Technology

Inside this colossal structure, engineers are also advancing the construction of the polygon base that will support the ELT’s primary mirror (M1)—a groundbreaking 128-foot (39-meter) mirror, which will become the largest ever made for an optical telescope. A secondary mirror (M2), expected to measure 14 feet (4.25 meters), is also under construction. In total, the telescope will comprise five mirrors.

The Intricate Spider Structure

A stunning close-up of the “spider” structure—named for its unique design with six arms fanning out from a central point—has been unveiled. This intricate skeleton is set to host M2, while M1 will consist of 798 hexagonal glass-ceramic segments, each 2 inches (5 centimeters) thick and 5 feet (1.5 meters) wide.

Elevating Cosmic Exploration

The altitude structure—a metal frame standing at 164 feet (50 meters)—will house all five mirrors and facilitate the telescope's rotation, enabling it to target various celestial objects across the sky. With such cutting-edge design and technology, the ELT promises to expand our cosmic horizons in extraordinary ways.

Conclusion

Stay tuned for more updates on this astronomical marvel as construction presses forward toward its grand unveiling! The future of observational astronomy is brighter than ever!