The European Southern Observatory (ESO) has revealed new images of the Extremely Large Telescope (ELT) under construction in Chile’s Atacama Desert, showcasing the rapid progress on its monumental dome structure.
The Scale of the Project
The ELT, captured in photos from December 2025 and released February 11, 2026, is designed to house a 39-meter (128-foot) primary mirror – four times larger than any existing telescope mirror. Its dome stands at 80 meters (260 feet) tall, making it one of the largest structures ever built for astronomical observation. This massive scale is not just about size; it’s about pushing the boundaries of what ground-based telescopes can achieve.
Engineering Challenges and Solutions
Constructing a telescope of this magnitude presents unique engineering hurdles. The ELT’s dome features massive, motorized doors currently being fitted with aluminum cladding to regulate temperature fluctuations. The desert environment poses extreme challenges: intense daytime heat and rapid nighttime cooling. The cladding helps mitigate these effects, ensuring optimal conditions for the delicate optics inside.
More critically, the telescope is built on a shock-absorbing base designed to withstand earthquake tremors – a necessity in the seismically active Atacama region. The entire upper section will rotate on a concrete pier, granting full access to the night sky while protecting the equipment.
Timeline and Scientific Goals
The dome is expected to be finished by 2027, with the installation of the five primary mirror segments following shortly after. Astronomers anticipate “first light” – initial test observations – in early 2029, with full scientific operations beginning in December 2029.
The ELT’s primary goal is to provide unprecedented resolution for ground-based astronomy. Its capabilities will allow scientists to study distant cosmic objects with unparalleled clarity, search for Earth-like exoplanets, and significantly advance our understanding of the universe.
The ELT represents a major leap in observational astronomy, offering the potential to unlock some of the deepest mysteries of the cosmos.
The telescope’s sheer size and advanced engineering promise a revolution in our ability to explore the universe.
