800px-The E-ELT

An artist's impression of the ELT

The Extremely Large Telescope (ELT) is an astronomical observatory and the world's largest optical/near-infrared extremely large telescope now under construction. Part of the European Southern Observatory (ESO) agency, it is located on top of Cerro Armazones in the Atacama Desert of northern Chile. The design consists of a reflecting telescope with a 39.3 metre diameter (126 foot) segmented primary mirror and a 4.2 metre diameter secondary mirror, and will be supported by adaptive optics, eight laser guide star units and multiple large science instruments.[1] The observatory aims to gather 100 million times more light than the human eye, 13 times more light than the largest optical telescopes existing in 2014, and be able to correct for atmospheric distortion. It has around 256 times the light gathering area of the Hubble Space Telescope and, according to the ELT's specifications, would provide images 16 times sharper than those from Hubble.[2]


The ELT is intended to vastly advance astrophysical knowledge by enabling detailed studies of planets around other stars, the first galaxies in the Universe, supermassive black holes, and the nature of the Universe's dark sector, and to detect water and organic molecules in protoplanetary disks around other stars.[3] The facility is expected to take 11 years to construct.[4]


On 11 June 2012, the ESO Council approved the ELT programme's plans to begin civil works at the telescope site, with construction of the telescope itself pending final agreement with governments of some member states.[5] Construction work on the ELT site started in June 2014.[6] By December 2014, ESO had secured over 90% of the total funding and authorized construction of the telescope to start, which will cost around one billion euros for the first construction phase.[7] The first stone of the telescope was ceremonially laid on 26 May 2017,[8] initiating the construction of the dome’s main structure and telescope. First light is currently planned for 2024.[9]


  1. Govert Schilling (14 June 2011). "Europe Downscales Monster Telescope to Save Money". Science Insider. Retrieved 17 August 2011. 
  3. "ESO – Are We Alone?". Retrieved 15 June 2011. 
  4. "The E-ELT construction proposal". ESO. Retrieved 16 January 2011. 
  5. Amos, Jonathan (11 June 2012). "European Extremely Large Telescope given go-ahead". BBC News. Retrieved 11 June 2012. 
  6. James Vincent (19 June 2014). "European Extremely Large Telescope to break ground (using dynamite) live later today". The Independent. 
  7. "Construction of Extremely Large Telescope Approved". Spaceref. 4 December 2014. 
  8. "Construction begins on world's largest telescope in Chilean desert". 26 May 2017. 
  9. "Groundbreaking for the E-ELT". ESO. 19 June 2014.