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Infographic: a closer look at Extremely Large Telescopes


Gain some perspective on the scale of Extremely Large Telescopes. Plus, we take a closer look at the Giant Magellan Telescope, the Thirty Metre Telescope and the European Extremely Large Telescope. 



Also see: our feature article which examines the new generation of Extremely Large Telescopes and how they will show us, for the first time, what exoplanets are really like.

GIANT MAGELLAN TELESCOPE (GMT) 24.5-METRE MIRROR

Organisation: US-led partnership with Australia, Brazil, Chile and Korea.

Telescope location: Las Campanas Observatory (2,550 metres high), Atacama Region, Chile.

Mirror size: Seven 8.4-metre diameter circular mirrors mounted together to give the collecting area of a 24.5-metre telescope.

Instruments: adaptive optics imaging cameras, spectrographs for high and low resolution, single and multiple targets.

Status: Partially funded. Mirror casting began 2005, four completed. Mirror polishing completed for one mirror. Site construction began in 2015.

Expected completion: 2022 with four mirrors, 2025 with seven mirrors.

Quirky fact: A life-sized depiction of the telescope’s seven mirrors is painted on the car park at the offices of the Observatories of the Carnegie Institution in Pasadena, California.

Rendering of the Giant Magellan Telescope showing the design of the telescope, enclosure and summit in 2015. Produced by Mason Media Inc.
Rendering of the Giant Magellan Telescope showing the design of the telescope, enclosure and summit in 2015. Produced by Mason Media Inc.
Giant Magellan Telescope – GMTO Corporation

THIRTY METRE TELESCOPE (TMT) 30-METRE MIRROR

Organisation: US-led partnership with Canada, China, India and Japan.

Telescope location: Preferred site is Mauna Kea Observatory (4,205 metres high), Big Island, Hawaii, but has been suject to dispute. Alternative site is Observatorio del Roque de los Muchachos (2,396 metres high), La Palma, Canary Islands.

Mirror size: 30-metre mirror composed of 492 hexagonal component mirrors (each about 1.4 metres in diameter) butted together under computer control to form a contiguous optical surface.

Instruments: adaptive optics imaging cameras, wide-field optical and infrared spectrographs for high and low resolution with single and multiple targets.

Status: Partially funded. Construction on hold pending the outcome of siting decision.

Expected completion: Intended to be finished in 2022 but depends on resolution of siting question.

Quirky fact: The 66-metre diameter dome proposed for the TMT has a moveable circular aperture rather than the usual opening slit.

Side view of Thirty Metre Telescope complex.
Side view of Thirty Metre Telescope complex.
Courtesy TMT International Observatory

EUROPEAN EXTREMELY LARGE TELESCOPE (E-ELT) 39.3-METRE MIRROR

Organisation: European Southern Observatory (ESO), a consortium of 15 European countries plus Brazil. In July 2017, Australia entered a 10-year strategic partnership with ESO which does not include access to the telescope.

Telescope location: Cerro Armazones Observatory (3,060 m high), Antofagasta, Chile

Mirror size: 39.3-metre diameter mirror composed of 798 hexagonal component mirrors (each about 1.4-metres in diameter) butted together under computer control to form a contiguous optical surface.

Instruments: adaptive optics imaging cameras, wide-field optical and infrared spectrographs for high and low resolution with single and multiple targets.

Status: Fully funded. First stone laid at Cerro Armazones in May 2017.

Expected completion: 2024.

Quirky fact: When completed, the E-ELT will be the biggest optical telescope ever built, equivalent in light-gathering power to 264 Hubble Space Telescopes.

Artist's impression of the European Extremely Large Telescope (E-ELT) in its enclosure on Cerro Armazones, in Chile's Atacama Desert. The design for the E-ELT shown here is preliminary.
Artist's impression of the European Extremely Large Telescope (E-ELT) in its enclosure on Cerro Armazones, in Chile's Atacama Desert. The design for the E-ELT shown here is preliminary.
ESO/L. Calçada

Fred Watson is an astronomer at the Australian Astronomical Observatory. His books include 'Stargazer: The Life and Times of the Telescope' and 'Star-Craving Mad: Tales from a Travelling Astronomer'.
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