Overwhelmingly Large Telescope

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Overwhelmingly Large Telescope
OverWhelmingly Large Telescope.jpg
Alternative namesOWL Edit this at Wikidata
OrganizationEuropean Southern Observatory Edit this on Wikidata
Wavelength0.32 μm (940 THz)–12 μm (25 THz)
Telescope styleCassegrain reflecting telescope
optical telescope Edit this on Wikidata
Diameter60, 100 m (196 ft 10 in, 328 ft 1 in) Edit this at Wikidata
Collecting area2,827, 7,854 m2 (30,430, 84,540 sq ft) Edit this at Wikidata
Focal length175 m (574 ft 2 in) Edit this at Wikidata
Websitewww.eso.org/sci/facilities/eelt/owl/ Edit this at Wikidata
Commons page Related media on Wikimedia Commons
Comparison of nominal sizes of apertures of the Overwhelmingly Large Telescope and some notable optical telescopes

The Overwhelmingly Large Telescope (OWL) was a conceptual design by the European Southern Observatory (ESO) organization for an extremely large telescope, which was intended to have a single aperture of 100 meters in diameter. Because of the complexity and cost of building a telescope of this unprecedented size, ESO has elected to focus on the 39-meter diameter Extremely Large Telescope instead.


OWL was first proposed in 1998, and at that time was estimated to be technologically feasible by 2010–2015.[1]

While the original 100 m design would not exceed the angular resolving power of interferometric telescopes, it would have exceptional light-gathering and imaging capacity that would greatly increase the depth to which humanity could explore the universe.[2] The OWL could be expected to regularly see astronomical objects with an apparent magnitude of 38, or 1,500 times fainter than the faintest object that has been detected by the Hubble Space Telescope.

All proposed designs for the OWL are variations on a segmented mirror, since there is no technology available to build and transport a monolithic 60- or 100-meter mirror. The operation of a segmented mirror is somewhat more complicated than a monolithic one, requiring careful alignment of the segments (a technique called cophasing). Experience gained in existing segmented mirrors (for example, the Keck telescope) suggests that the mirror proposed for the OWL is feasible. However, the projected cost (of around €1.5 billion) was considered too high, so the ESO is now building the smaller European Extremely Large Telescope around 39 m in diameter.[3][4][5] Also, there appears to be some inconsistency as to the actual construction costs of the OWL, with some estimating its cost an order of magnitude higher (EELT currently at €1.3 billion,[6] equivalent to around $1.6 billion, scaled using D^2.77 proportionality assuming a 100 meter diameter yields $21 billion).[7]

It has been estimated that a telescope with a diameter of 80 meters would be able to spectroscopically analyse Earth-size planets around the forty nearest sun-like stars.[8] As such, this telescope could help in the exploration of exoplanets and extraterrestrial life (because the spectrum from the planets could reveal the presence of molecules indicative of life).

See also[edit]


  1. ^ Gilmozzi, R.; et al. (1998). European Southern Observatory. "The future of filled aperature telescopes: Is a 100m feasible?" (PDF). Advanced Technology Optical/IR Telescopes. SPIE. VI (3352): 778. Bibcode:1998SPIE.3352..778G. doi:10.1117/12.319284. S2CID 12512243. Retrieved 25 Oct 2018.
  2. ^ http://www.eso.org/sci/facilities/eelt/owl/index_3.html
  3. ^ "OWL 100-m telescope". www.eso.org. Retrieved 2019-10-08.
  4. ^ http://www.eso.org/projects/e-elt/
  5. ^ "Record mirror for Euro telescope". BBC News. 2006-08-07. Retrieved 2010-03-27.
  6. ^ information@eso.org. "Funding boost for ESO's Extremely Large Telescope". www.eso.org. Retrieved 2020-12-05.
  7. ^ van Belle, Gerard T. [www2.lowell.edu/users/gerard/publications/van_belle_meinel2_2004.pdf "The Scaling Relationship Between Telescope Cost and Aperture Size for Very Large Telescopes"] Check |url= value (help) (PDF). Lowell Observatory.
  8. ^ Gilmozzi, Roberto (May 2006). "Giant Telescopes of the Future". Scientific American.

External links[edit]