December 19, 2006, Garching, Germany--The European Southern Observatory (ESO) will proceed with detailed studies for the European Extremely Large Telescope (E-ELT), which if built will be by far the largest telescope ever constructed. With a 42 m aperture, the E-ELT will collect many times more light than the largest existing telescopes, such as the 10 m Keck telescopes (Mauna Kea, HI) or the ESO's four 8.2 m VLTs (Very Large Telescopes) located on Cerro Paranal in Chile.
With a budget of 57 million Euro, the study will prepare the way for construction of the optical/infrared telescope. "At the end of the three-year Final Design Study we will know exactly how everything is going to be built, including a detailed costing," said Catherine Cesarsky, ESO's Director General. "We then hope to start construction and have it ready by 2017, when we can install instruments and use it."
The E-ELT will rely on adaptive optics--a must for ground-based telescopes if they are to compete in resolution with the Hubble Space Telescope. The present concept, estimated to cost around 800 million Euro, has as its baseline the telescope housed in an 80 m diameter rotating dome.
The telescope's primary 42 m diameter mirror will be composed of 906 hexagonal segments, each 1.45 m in size, while the secondary mirror will be as large as 6 m in diameter. A tertiary mirror 4.2 m in diameter will relay the light to the adaptive-optics system, composed of two mirrors: a 2.5 m mirror supported by 5000 or more actuators with a bandwidth of 1 kHz, and one 2.7 m in diameter that allows for the final image corrections. This five-mirror approach will result in resolution that approaches the diffraction limit.
With such capabilities, the telescope is bound to result in discovery as it peers at the edge of the universe--or, with its unmatched light-gathering power, at closer objects previously too faint to image. "We will search for planets similar to the Earth around other stars, discover the nature of matter by mapping the distribution and properties of the dark matter, which is the matter of which Nature is made, not the rather unimportant amount of stuff of which we are made, and investigate the future of the Universe--is time infinite?--by examining the dark energy which seems to control the fate of space-time," said Gerry Gilmore, a professor at the University of Cambridge (Cambridge, England).
42 to explain a lot
Isobel Hook of Oxford University (Oxford, England) led the team in developing the science case for an E-ELT. "There are a lot of big questions in astronomy that we can't answer with the current generation of telescopes," said Hook. "42 may not quite be the answer to Life, the Universe and Everything, but it will tell us a great deal more than we know now."
For the past year, ESO has been working together with European astronomers to define this telescope, needed by the end of the next decade. This fast pace has also been possible thanks to early conceptual studies (such as the ESO OWL and the EURO-50 studies), complemented by a large mobilization of European institutes and high-tech industries to develop critical technologies in the framework of the so-called ELT Design Study, with ESO and the European Commission as the main funders, as well as with national contributions.
The site of the E-ELT is not yet fixed, as studies are still underway with a plan to make a decision by 2008.