The Overwhelmingly Large Telescope (OWL) was a conceptual design by the European Southern Observatory (ESO) organisation for an extremely large telescope, which was intended to have a single aperture of 100 metres in diameter. Because of the complexity, cost, and risk of building a telescope of this unprecedented size, ESO decided to focus on the 39-metre diameter Extremely Large Telescope 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, it would have exceptional light-gathering and imaging capacity. 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 that of 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<!-- The €1.5 billion ($1.65 billion) figure listed seems kind of questionable. The ESO website admits the figure given is a preliminary estimate based on engineering/analytical models, and is not final. Given that both the 30 Meter Telescope and the European Extremely Large Telescope are in the ballpark of $1-$2 billion, it seems unlikely a structure or telescope 3x bigger in diameter (9x bigger in area, and 27x bigger in volume) would be so close in cost.

I could be wrong, however if we could find updated estimates, I think the estimated cost of the OWLT will be much higher than their preliminary estimate from years ago. (Is this how I'm supposed to use invisible comments? I hope so, please delete if not.) -->) was considered too high, so the ESO is now building the smaller Extremely Large Telescope 39.5 m in diameter. Also, the realism of the estimated construction costs of the OWL has been questioned, with some estimating its cost an order of magnitude higher (the 39m ELT currently at €1.3 billion, equivalent to around $1.3 billion, scaled using 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 exoplanets and extraterrestrial life (because the spectrum from the planets could reveal the presence of molecules indicative of life).

See also

  • Active optics
  • Adaptive optics
  • Extremely Large Telescope
  • Giant Magellan Telescope
  • List of optical telescopes
  • List of largest optical reflecting telescopes
  • Thirty Meter Telescope

References

  • The ESO 100-m optical telescope concept
  • OWL BLUE BOOK – Phase A design report