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Observatory

ESO Extremely Large Telescope (ELT)

ESO's Extremely Large Telescope is a 39 m telescope being built on Cerro Armazones, Chile. First light is due in 2029, science in December 2030.

Location
Cerro Armazones, Atacama Desert, Antofagasta Region
Focus
Exoplanets, Astrobiology, Galaxies, Black holes, Cosmology, Telescopes and missions
Coordinates
-24.589, -70.192
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Location of ESO Extremely Large Telescope (ELT) on a globe

The Extremely Large Telescope (ELT) is the European Southern Observatory’s next flagship, under construction on Cerro Armazones in Chile’s Atacama Desert. When finished it will be the world’s largest optical and mid-infrared telescope, with a 39.3-meter primary mirror made of 798 segments and a 4.25-meter secondary. ESO’s specifications give it about 250 times Hubble’s light-gathering area and images about 15 times sharper than Hubble’s.

Flagship instruments

  • HARMONI, MICADO, METIS and MORFEO: the first-generation instruments.
  • ANDES and MOSAIC: to follow.
  • METIS and MICADO are being built with the Max Planck Institute for Astronomy in Heidelberg.

Recent progress

There is no science yet, so the milestones are engineering ones. Work on the access road began in March 2014, and dome and main-structure construction started in May 2018. The first primary-mirror segments arrived in Chile in January 2024. On March 14, 2025, ESO moved first light to March 2029 and the start of science to December 2030, citing weather, longer technology development and manufacturing failures.

The science case builds on results from today’s telescopes. Nearby worlds such as Proxima b, found in 2016 with ESO instruments, and atmospheres first read by JWST, such as carbon dioxide on WASP-39b, are the kind of targets a 39-meter mirror is meant to study in far more detail.

What to watch, 2026-2030

  • 2026: secondary mirror (M2) completed.
  • 2027: dome and telescope structure complete; M3 complete.
  • 2028: M4 adaptive mirror, M5 and all 798 primary segments installed.
  • March 2029: first light.
  • December 2030: scientific first light.

Why scientists are converging here

On current schedules the ELT is the first of the giant telescopes to see the sky. The Giant Magellan Telescope is expected to be completed in the 2030s, and the Thirty Meter Telescope has no US federal construction funding. For rocky-planet atmospheres, astrobiology and the first galaxies, the ELT is where European and partner teams are placing their bets for the 2030s, next door to the Very Large Telescope.

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