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Extremely large telescope
Astronomical observatory featuring an optical telescope with an aperture of more than 20 m diameter

An extremely large telescope (ELT) is an astronomical observatory featuring an optical telescope with an aperture for its primary mirror from 20 metres up to 100 metres across, when discussing reflecting telescopes of optical wavelengths including ultraviolet (UV), visible, and near infrared wavelengths. Among many planned capabilities, extremely large telescopes are planned to increase the chance of finding Earth-like planets around other stars. Telescopes for radio wavelengths can be much bigger physically, such as the 300 metres (330 yards) aperture fixed focus radio telescope of the Arecibo Observatory (now defunct). Freely steerable radio telescopes with diameters up to 100 metres (110 yards) have been in operation since the 1970s.

These telescopes have a number of features in common, in particular the use of a segmented primary mirror (similar to the existing Keck telescopes), and the use of high-order adaptive optics systems.

Although extremely large telescope designs are large, they can have smaller apertures than the aperture synthesis on many large optical interferometers. However, they may collect much more light, along with other advantages.

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List of telescopes

#ImageNameAperture (m)Area (m2)Primary mirrorAltitude (m)FirstlightNotesRefs
1Extremely Large Telescope(ELT)39.3978798 × 1.45 mhexagonal f/130602029Under construction at Cerro Armazones Obs., Chile678
2Thirty Meter Telescope(TMT)30.0655492 × 1.45 mhexagonal f/14050CancelledConstruction approved at Mauna Kea Obs. in Hawaii, USA, halted as of September 2019 due to protests9101112
3Giant Magellan Telescope(GMT)24.53687 × 8.4 mcircular f/0.7125162030sUnder construction at Las Campanas Obs., Chile;6/7 mirrors cast131415
4Large Binocular Telescope(LBT)11.8 (equiv. area)22.8 (equiv. detail limit)1112 × 8.4 mcircular32212008Largest non-segmented mirrors.Located on Mount Graham, Arizona, USA16
Note: Aperture of LBT: the baseline is obtained via aperture synthesis.

Budget

Possible budget figures, which are estimates and can vary over time. For construction costs, it is recommended to estimate the cost of a giant telescope with the relation cost ∝ D2.7.17

NameCost(est. USD)Alternate
Extremely Large Telescope (ELT)$1590 million€1300 million18
Thirty Meter Telescope (TMT)$1400 million$3600 million19
Giant Magellan Telescope (GMT)$1000 million$2540 million20
Large Binocular Telescope (LBT)$120 million

Projects

There were several telescopes in various stages in the 1990s and early 2000s, and some developed into construction projects.

Under construction Funded construction Projects

Some of these projects have been cancelled, or merged into ongoing extremely large telescopes.

  • GSMT:24 Giant Segmented Mirror Telescope, merged into TMT
  • OWL:25 Overwhelmingly Large Telescope, passed over in favor of ELT
  • VLOT:26 Very Large Optical Telescope, merged into TMT
  • LAT:27 Large Atacama Telescope
  • EURO50:28 European 50-metre Telescope, merged into ELT
  • LPT:29 Large Petal Telescope
  • Magellan 20: merged into GMT
  • HDRT:30 High Dynamic Range Telescope
  • JELT:31 Japanese ELT Project; Japan joined the TMT project in 2008
  • CELT:32 California Extremely Large Telescope, became/merged into TMT
  • MAXAT:33 Maximum Aperture Telescope

See also

References

  1. As A Skeleton Science Case For Extremely Large (20m–100m) Ground-based Telescopes (ELTs) and first section of ELT Roadmap Archived 2015-05-18 at the Wayback Machine, PDF http://www.astro-opticon.org/fp5/skelcase.html ↩

  2. 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. /wiki/Dennis_Overbye ↩

  3. Jha, Alok (5 August 2006). "Extremely Large Telescope could reveal secrets of life, the universe and everything". The Guardian. https://www.theguardian.com/science/2006/aug/05/spaceexploration.universe ↩

  4. "Thirty Meter Telescope Construction Proposal" (PDF). TMT Observatory Corporation. 2007-09-12: 29. Archived from the original (PDF) on 2016-03-24. Retrieved 2009-07-24. {{cite journal}}: Cite journal requires |journal= (help) https://web.archive.org/web/20160324230243/http://tmt.org/news/TMT-Construction%20Proposal-Public.pdf ↩

  5. "Chapter 6: Optics" (PDF). GMT Conceptual Design Report. GMT Consortium. pp. 6–3. Retrieved 2008-04-02. http://www.gmto.org/codrfolder/GMT-ID-01467-Chapter_6_Optics.pdf ↩

  6. "Groundbreaking for the E-ELT". 19 June 2014. http://www.eso.org/public/news/eso1419/ ↩

  7. Schilling, Govert (14 June 2011). "Europe Downscales Monster Telescope to Save Money". Science Insider. https://www.science.org/content/article/europe-downscales-monster-telescope-save-money ↩

  8. "The E-ELT in numbers". Archived from the original on 2009-08-21. Retrieved 2009-08-11. https://web.archive.org/web/20090821225427/http://www.eso.org/public/astronomy/teles-instr/e-elt_num.html ↩

  9. "Thirty Meter Telescope Construction Proposal" (PDF). TMT Observatory Corporation. 2007-09-12: 29. Archived from the original (PDF) on 2016-03-24. Retrieved 2009-07-24. {{cite journal}}: Cite journal requires |journal= (help) https://web.archive.org/web/20160324230243/http://tmt.org/news/TMT-Construction%20Proposal-Public.pdf ↩

  10. Thirty Meter Telescope timeline page, TMT Observatory Project, archived from the original on 2010-09-25, retrieved 2010-10-12 https://web.archive.org/web/20100925013506/http://www.tmt.org/observatory/timeline ↩

  11. TMT Timeline, accessed February 11, 2018 https://www.tmt.org/page/timeline?category=Observatory+Construction ↩

  12. "Hawaii top court approves controversial Thirty Meter Telescope". BBC News. 31 October 2018. https://www.bbc.com/news/world-us-canada-46046864 ↩

  13. "Chapter 6: Optics" (PDF). GMT Conceptual Design Report. GMT Consortium. pp. 6–3. Retrieved 2008-04-02. http://www.gmto.org/codrfolder/GMT-ID-01467-Chapter_6_Optics.pdf ↩

  14. Howell, Elizabeth (29 December 2014). "Giant telescope gets $20m funding boost as design takes shape". Sen. Archived from the original on 17 July 2021. Retrieved 8 January 2015. https://web.archive.org/web/20210717164947/https://sen.com/news/giant-telescope-gets-20m-funding-boost-as-design-takes-shape ↩

  15. "Giant Magellan Telescope – 6th mirror cast". 12 March 2021. Retrieved 11 July 2023. https://www.universetoday.com/150506/the-giant-magellan-telescopes-6th-mirror-has-just-been-cast-one-more-to-go/ ↩

  16. "Large Binocular Telescope Achieves First Binocular Light" (Press release). Large Binocular Telescope Corporation. 2008-02-28. Archived from the original on 2008-03-10. https://web.archive.org/web/20080310010642/http://medusa.as.arizona.edu/lbto/firstbinocularlight_press_release.htm ↩

  17. Stepp, Larry; Daggert, Larry; Gillett, Paul. "Estimating the costs of extremely large telescopes" (PDF). National Optical Astronomy Observatory. http://www.gsmt.noao.edu/documentation/SPIE_Papers/Stepp.pdf ↩

  18. "Funding boost for ESO's Extremely Large Telescope". The European Southern Observatory (ESO). Retrieved 29 August 2024. https://www.eso.org/public/announcements/ann20034/ ↩

  19. "NSF board approves funding for just one of two proposed giant telescopes". Science (Science.org). Retrieved 29 August 2024. https://www.science.org/content/article/nsf-board-approves-funding-just-one-two-proposed-giant-telescopes ↩

  20. "NSF board approves funding for just one of two proposed giant telescopes". Science (Science.org). Retrieved 29 August 2024. https://www.science.org/content/article/nsf-board-approves-funding-just-one-two-proposed-giant-telescopes ↩

  21. "Elt | Eso". http://www.eso.org/public/teles-instr/elt/ ↩

  22. "Giant Magellan Telescope". Giant Magellan Telescope. https://gmto.org/ ↩

  23. "TMT International Observatory". TIO. https://www.tmt.org/ ↩

  24. "AURA NIO: Home". October 19, 2006. Archived from the original on 2006-10-19. https://web.archive.org/web/20061019105956/http://www.aura-nio.noao.edu/ ↩

  25. "The ESO 100-m OWL optical telescope concept". www.eso.org. https://www.eso.org/sci/facilities/eelt/owl/ ↩

  26. "VLOT } The Very Large Optical Telescope for CI am Canada". May 2, 2009. Archived from the original on 2009-05-02. https://web.archive.org/web/20090502050342/http://www.hia-iha.nrc-cnrc.gc.ca/VLOT/ ↩

  27. "Atacama". Archived from the original on 2003-12-02. Retrieved 2006-12-13. https://web.archive.org/web/20031202212639/http://astrosun.tn.cornell.edu/atacama ↩

  28. "Euro50". December 14, 2006. Archived from the original on 2006-12-14. https://web.archive.org/web/20061214083436/http://www.astro.lu.se/~torben/euro50/ ↩

  29. "LPT | Large Petal Telescope". November 23, 2006. Archived from the original on 2006-11-23. https://web.archive.org/web/20061123185947/http://serweb.oamp.fr/denis/elt/ngcfht_may01.html ↩

  30. https://home.ifa.hawaii.edu/users/kuhn/tmp.html%25%7Ctitle= 22 March 2002. https://home.ifa.hawaii.edu/users/kuhn/tmp.html%25%7Ctitle= ↩

  31. http://optik2.mtk.nao.ac.jp/futureplan/eltproje.htm[permanent dead link] http://optik2.mtk.nao.ac.jp/futureplan/eltproje.htm ↩

  32. "index.html". June 5, 2002. Archived from the original on 2002-06-05. https://web.archive.org/web/20020605200532/http://celt.ucolick.org/ ↩

  33. "MAXAT – the Maximum Aperture Telescope". Archived from the original on 6 July 2007. https://web.archive.org/web/20070706082910/http://www.gemini.edu/science/maxat/ ↩