The dome surrounding the world’s largest telescope is taking shape, with siding and supports to protect the primary mirror being installed.
The European Southern Observatory’s (ESO) Extremely Large Telescope (ELT) is currently under construction on Cerro Almazones mountain in Chile’s Atacama Desert, and is scheduled to make its first observations by 2028.
Recent progress photos from the construction site, taken in June 2024, show cladding being installed on the outside of the ELT dome. This layer of material will act as an insulating barrier, provide weather resistance, and help protect the telescope from the harsh environment of the Chilean desert.
Part of the dome will have large sliding doors that can be closed during the day and opened at night to allow the telescope to scan the sky. Once complete, the telescope will have a variety of missions, including searching for Earth-like exoplanets for signs of life outside our solar system, and probing the early universe to study the first galaxies that formed after the Big Bang.
Erection has begun on the sliding door beam structure, which helps protect the telescope from the high daytime temperatures and dusty desert environment.
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The frame of the dome’s sliding door, which protects the Extremely Large Telescope (ELT) during the day and opens up for observations at night. (Image credit: ESO)
Construction photos from June also show progress on the support structure in the center of the dome, which will hold the ELT’s 128-foot (39-meter)-wide primary mirror (M1), which weighs a whopping 200 tons. The mirror rests on a white lattice structure that allows M1 to move smoothly during observations and compensate for changing gravitational loads, wind conditions, vibrations, and temperature changes.
“Look at the cranes and vehicles below, which give a good idea of just how enormous the ELT is!” ESO officials said in a statement announcing the updated images.
The support structure will be assembled in the centre of the dome, which will eventually house the 200-tonne primary mirror of the Extremely Large Telescope (ELT). (Image credit: ESO)
The primary mirror is made up of 798 hexagonal segments, making it the largest segmented mirror ever made for a telescope. The ELT has a total of five mirrors, each with a different shape, size and function, but they work together to observe the universe.
Secondary mirror M2 is suspended above M1 and reflects the light it collects to tertiary mirror M3. The central hole in the white lattice structure houses the central tower, which houses mirrors M3, M4 and M5.
