The Overwhelmingly Large Telescope (OWL) was a conceptual design by the

European Southern Observatory The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental organization, intergovernmental research organisation made up of 16 mem ...

(ESO) organization for an

extremely large telescope The Extremely Large Telescope (ELT) is an astronomical observatory currently under construction. When completed, it is planned to be the world's largest optical/near-infrared extremely large telescope. Part of the European Southern Observator ...

, 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 The Extremely Large Telescope (ELT) is an astronomical observatory currently under construction. When completed, it is planned to be the world's largest optical/near-infrared extremely large telescope. Part of the European Southern Observator ...

instead.

History

OWL was first proposed in 1998, and at that time was estimated to be technologically feasible by 2010–2015. While the original 100 m design would not exceed the angular resolving power of

interferometric telescopes Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opti ...

, it would have exceptional light-gathering and imaging capacity that would greatly increase the depth to which mankind could explore the universe. The OWL could be expected to regularly see astronomical objects with an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

of 38, or 1,500 times fainter than the faintest object that has been detected by the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

. All proposed designs for the OWL are variations on a

segmented mirror A segmented mirror is an array of smaller mirrors designed to act as segments of a single large curved mirror. The segments can be either spherical or asymmetric (if they are part of a larger parabolic reflector). They are used as objectives for ...

, 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 The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state In the United States, a state is a constituent political entit ...

) 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

around 39 m in diameter. 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 (ELT currently at €1.3 billion, equivalent to around $1.3 billion, scaled using D^2.77 proportionality assuming a 100 meter diameter yields $21 billion). 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. As such, this telescope could help in the exploration of

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

s and

extraterrestrial life Extraterrestrial life, colloquially referred to as alien life, is life that may occur outside Earth and which did not originate on Earth. No extraterrestrial life has yet been conclusively detected, although efforts are underway. Such life might ...

(because the spectrum from the planets could reveal the presence of molecules indicative of life).

References

External links

*
The ESO 100-m optical telescope concept
– Phase A design report
ESO - ELT
{{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System European Southern Observatory Optical telescopes Astronomical observatories in Chile Unbuilt buildings and structures

History

See also

References

External links