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As of early 2025, 60% of the construction of the Extremely Large Telescope (ELT) is complete. The telescope is expected to begin its first scientific observations by the end of 2028.

About ELT

The Extremely Large Telescope (ELT) is poised to become the world’s most powerful ground-based optical and infrared telescope, with revolutionary capabilities to explore the universe.

• Location: Cerro Armazones, Atacama Desert, northern Chile
• Altitude: 3,046 meters above sea level
• Managing Body: European Southern Observatory (ESO)
• Project Cost: Approximately $1.51 billion (around 1.3 billion euros)
• Completion Target: Late 2020s
• Primary Mirror: Diameter of 39 meters (128 feet) — the largest of its kind
  • Constructed from 798 hexagonal segments, each 1.5 m across and 5 cm thick

Key Scientific Objectives

• Exoplanet Exploration
  • Direct imaging of Earth-like exoplanets in habitable zones of nearby stars
  • Analysis of atmospheric biosignatures such as oxygen, water vapor, and methane, aiding the search for extraterrestrial life
• Understanding the Early Universe
  • Observation of the first stars and galaxies formed post-Big Bang
  • Investigation of dark matter and dark energy, crucial for understanding cosmic expansion and the universe’s fate
• Detailed Study of Stars and Galaxies
  • Identification and characterization of individual stars in distant galaxies
  • Analysis of the formation, evolution, and structure of galaxies over cosmic time
• Black Holes and Cosmic Structures
  • Study of supermassive black holes at galactic centers
  • Understanding their role in galaxy dynamics and structure

Why Chile’s Atacama Desert?

• Dry Climate: Very low humidity and cloud cover, ensuring clearer skies
• High Altitude: Thin atmosphere reduces atmospheric interference with incoming light
• Minimal Light Pollution: Remote location offers dark skies critical for deep-space observation
• Dome Structure: Protects sensitive instruments from harsh desert conditions

About the European Southern Observatory (ESO)

• Nature: Leading intergovernmental science and technology organization in the field of astronomy
• Headquarters: Garching, Germany
• Members: 16 countries including Austria, Belgium, Brazil, France, Germany, Italy, Spain, and the United Kingdom
• Facilities in Chile:
  • La Silla
  • Paranal
  • Chajnantor
• Mandate: Design, construction, and operation of advanced ground-based telescopes to promote international collaboration and facilitate path-breaking astronomical research