Giant Magellan Telescope

ground-based telescope under construction, planned for completion in 2029

The Giant Magellan Telescope (GMT) will be the world's largest telescope when it is completed in 2025. Instead of one large mirror, the GMT will have seven separate mirrors working together. This will mean its collecting area is bigger than the actual mirror surfaces.[1] It will be made of seven 8.4 m (27.6 ft) diameter mirror parts.[2] It will have a the resolving power of a 24.5 m (80.4 ft) mirror. Its collecting area will be the same as a 21.4 m (70.2 ft) mirror. The telescope will have over four times the ability to gather light than existing telescopes. It will produce images up to ten times clearer than the Hubble Space Telescope.[3] It will cost $700 million.[4]

Giant Magellan Telescope
Alternative namesGMT Edit this at Wikidata
Part ofUS Extremely Large Telescope Program Edit this on Wikidata
Location(s)Atacama Desert, Coquimbo Region, Atacama Region, Chile Edit this at Wikidata
Coordinates29°02′54″S 70°41′01″W / 29.0483°S 70.6836°W / -29.0483; -70.6836 Edit this at Wikidata
Altitude2,516 m (8,255 ft) Edit this at Wikidata
Wavelength320 nm (940 THz)-25,000 nm (12 THz)
Built2015 Edit this on Wikidata–2025 Edit this on Wikidata (2015 Edit this on Wikidata–2025 Edit this on Wikidata) Edit this at Wikidata
Telescope styleGregorian telescope Edit this on Wikidata
Diameter25.448 m (83 ft 5.9 in) Edit this at Wikidata
Secondary diameter3.2 m (10 ft 6 in) Edit this at Wikidata
Mass2,100 t (2,100,000 kg) Edit this at Wikidata
Angular resolution0.01 arcsecond Edit this on Wikidata
Collecting area368 m2 (3,960 sq ft) Edit this at Wikidata
Focal length18, 202.7 m (59 ft 1 in, 665 ft 0 in) Edit this at Wikidata Edit this at Wikidata
Giant Magellan Telescope is located in Chile
Giant Magellan Telescope
Location of Giant Magellan Telescope
Las Campanas Observatory, the site for the Giant Magellan Telescope

Planned site


The location of the telescope is the Las Campanas Observatory,[3] which is also the site of the Magellan Telescopes, some 115 km (71 mi) northeast of La Serena, Chile. This area has clear weather for most of the year.[5] The night sky in most of the surrounding Atacama Desert region is free from atmospheric pollution. With few cities nearby this is probably one of the places least affected by light pollution. All of this makes the area one of the best spots on Earth for long-term astronomical observation.

Design details


The telescope is unique because it will use seven mirror sections, each 8.4 m (27.6 ft) in diameter. These segments will then be arranged to form a single optical surface. This is difficult as the surface of the outer six mirror segments is not radially symmetrical (that is, they are off-axis). This requires a small change in the way mirrors are usually polished. All seven mirrors will be arranged so that the reflecting surface of each of them is on a common axis. One mirror will be in the center and the other six arranged symmetrically around the center. A focal plane will be on-axis with the entire assembly. The plan is to build seven identical off-axis mirrors. The spare mirror has been made to replace a mirror when it needs recoating, a 1–2 week (per segment) process required every 1–2 years.[6]

The Steward Observatory, at the University of Arizona, is making the mirrors in a laboratory beneath the university's football stadium. It is using a rotating furnace to make the mirror. The casting of the first mirror was completed on November 3, 2005. But the time-consuming shaping and polishing will be completed in the autumn of 2011.

The telescope will make use of adaptive optics.[7]

Member organizations


The following is a list of the group which is developing the telescope.[8]

George P. Mitchell, founder of Mitchell Energy & Development Corp., and The Cynthia and George Mitchell Foundation are giving $25 million to help pay for the telescope.[4]



  1. Maggie McKee (2007-10-04). "Giant telescope in race to become world's largest". New Scientist. Retrieved 2007-10-07.
  2. "Giant Magellan Telescope Partner Institutions". GMT Consortium. Archived from the original on 2007-02-11. Retrieved 2007-04-03.
  3. 3.0 3.1 "Giant Magellan telescope site selected". Carnegie Institution. Retrieved 2007-10-05.
  4. 4.0 4.1 "George Mitchell Commits $25 Million to Giant Magellan Telescope". Giant Magellan Telescope Organization. Archived from the original on 2012-01-31. Retrieved 2011-09-07.
  5. Robinson, Travis (2007-04-03). "Eye on the sky". The Battalion. Archived from the original on 2007-09-29. Retrieved 2007-04-03.
  6. "Telescope Structure". GMT Conceptual Design Report. February 2006. Archived from the original on 2011-05-25. Retrieved 2007-10-07. Section 7.4.5, page 7-17.
  7. "Overview". Giant Magellan Telescope Organization. Archived from the original on 2011-06-09. Retrieved 2011-09-07.
  8. "Giant Magellan Telescope Partner Institutions". GMTO. Archived from the original on 2009-02-20. Retrieved 2009-02-11.

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