Sleep tight, ELT

Growing is hard work — and this Picture of the Week, taken on 3 April 2024, shows ESO’s Extremely Large Telescope (ELT) taking a well-deserved night-time rest. The view from inside the telescope’s dome shows progress on this giant structure, 80 metres high and 88 metres wide, which will protect the world’s biggest eye on the sky from the extreme environment of Chile’s Atacama Desert. 

The dome’s steel skeleton is complete, and now a protective insulated cladding — the dark blue panels seen above — is being applied over it. This cladding consists of different layers, including thermal insulation and aluminium sheets outside. Together with air conditioning — active during the day, when the dome is closed —, this will keep the air inside the dome at the same temperature as the outside environment, minimising turbulence that could otherwise blur the images the ELT will capture.

In the centre, on a separate concrete foundation to protect it from vibrations propagating through the ground, stands the azimuth structure that will hold the telescope and its array of scientific instruments. 

Right now, the ELT structure can enjoy a stunning view of the Milky Way during its night break. In the future, the telescope will be working nights — but will have access to the same view when the dome opens its large observing slit to see the sky.

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• Time-lapse taken the same night outside the dome.