Extremely Large Telescope

Extremely Large Telescope
	Artist's impression of the ELT
Alternative names	ELT
Part of	European Southern Observatory
Location(s)	Cerro Armazones, Antofagasta Province, Antofagasta Region, Chile
Coordinates	24°35′21″S 70°11′30″W / 24.5893°S 70.1916°W
Organization	European Southern Observatory
Altitude	3,046 m (9,993 ft)
Built	26 May 2017–
Telescope style	extremely large telescope; infrared telescope; Nasmyth telescope
Diameter	39.3 m (128 ft 11 in)
Secondary diameter	4.09 m (13 ft 5 in)
Tertiary diameter	3.75 m (12 ft 4 in)
Angular resolution	0.005 arcsecond
Collecting area	978 m2 (10,530 sq ft)
Focal length	743.4 m (2,439 ft 0 in)
Enclosure	dome
Website	elt.eso.org
	Location of Extremely Large Telescope
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The Extremely Large Telescope (ELT) is an astronomical observatory under construction.^[1] When completed, it will be the world's largest optical/near-infrared ELT. 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 (130-foot) segmented primary mirror and a 4.2 m (14 ft) diameter secondary mirror. The telescope will be supported by adaptive optics, six laser guide star units, and multiple large science instruments.^[2]^[3] The observatory's design will gather 100 million times more light than the human eye, equivalent to about 10 times more light than the largest optical telescopes existing as of 2023, and will correct for atmospheric distortion. It has around 250 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.^[4]

The project was originally called the European Extremely Large Telescope (E-ELT), but the name was shortened in 2017.^[5] The ELT is intended to 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.^[6] As planned in 2011, the facility was expected to take 11 years to construct, from 2014 to 2025.^[7]

On 11 June 2012, the ESO Council approved the ELT programme's plans to begin civil works at the telescope site, with the construction of the telescope itself pending final agreement with governments of some member states.^[8] Construction work on the ELT site started in June 2014.^[9] 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.^[10] The first stone of the telescope was ceremonially laid on 26 May 2017, initiating the construction of the dome's main structure and telescope.^[11]^[12] The telescope passed the halfway point in its development and construction in July 2023, with completion and first light planned at that time for 2028.^[13]^[3]

^ Overbye, Dennis (8 March 2024). "Good News and Bad News for Astronomers' Biggest Dream - The National Science Foundation takes a step (just one) toward an "extremely large telescope."". The New York Times. Archived from the original on 8 March 2024. Retrieved 8 March 2024.
^ Cite error: The named reference govert was invoked but never defined (see the help page).
^ ^a ^b "ESO's Extremely Large Telescope is now half completed". European Southern Observatory.
^ "The European Extremely Large Telescope ('ELT') Project". European Southern Observatory.
^ information@eso.org. "Renaming the E-ELT - Statement from ESO's Director General". www.eso.org. Retrieved 9 October 2023.
^ Cite error: The named reference E-ELT Alone was invoked but never defined (see the help page).
^ "The E-ELT construction proposal" (PDF). European Southern Observatory. Retrieved 16 January 2011.
^ Cite error: The named reference Approval was invoked but never defined (see the help page).
^ Cite error: The named reference beginning was invoked but never defined (see the help page).
^ Cite error: The named reference spaceref2014 was invoked but never defined (see the help page).
^ "Construction begins on world's largest telescope in Chilean desert". Reuters. 26 May 2017.
^ Cite error: The named reference eso1419-groundbreaking was invoked but never defined (see the help page).
^ "ELT Timeline".

[NYT-20240308-1] Overbye, Dennis (8 March 2024). "Good News and Bad News for Astronomers' Biggest Dream - The National Science Foundation takes a step (just one) toward an "extremely large telescope."". The New York Times. Archived from the original on 8 March 2024. Retrieved 8 March 2024.

[govert-2] Cite error: The named reference govert was invoked but never defined (see the help page).

[50percent-3] "ESO's Extremely Large Telescope is now half completed". European Southern Observatory.

[E-ELT-4] "The European Extremely Large Telescope ('ELT') Project". European Southern Observatory.

[5] rmation@eso.org. "Renaming the E-ELT - Statement from ESO's Director General". www.eso.org. Retrieved 9 October 2023.

[E-ELT_Alone-6] Cite error: The named reference E-ELT Alone was invoked but never defined (see the help page).

[eso_executive_summary-7] "The E-ELT construction proposal" (PDF). European Southern Observatory. Retrieved 16 January 2011.

[Approval-8] Cite error: The named reference Approval was invoked but never defined (see the help page).

[beginning-9] Cite error: The named reference beginning was invoked but never defined (see the help page).

[spaceref2014-10] Cite error: The named reference spaceref2014 was invoked but never defined (see the help page).

[11] "Construction begins on world's largest telescope in Chilean desert". Reuters. 26 May 2017.

[eso1419-groundbreaking-12] Cite error: The named reference eso1419-groundbreaking was invoked but never defined (see the help page).

[start2027-13] "ELT Timeline".

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