The future of European astronomy is poised to enter a new era of discovery with the decision announced by ESO's governing body to proceed with detailed studies for the European Extremely Large Telescope (E-ELT). This three year study, with a budget of 57 million euro, will prepare the way for construction of the world's largest optical/infrared telescope that will revolutionise ground-based astronomy. Astronomers from the UK have played crucial roles in reaching this decision.
The E-ELT will be more than hundred times more sensitive than the present-day largest optical telescopes, such as the 10-m Keck telescopes or the 8.2-m VLT telescopes and will answer some of the biggest questions about the Universe in which we live.
Professor Gerry Gilmore, University of Cambridge anticipates tremendous new science being made possible saying "The E-ELT is critical to allow the next big advance in understanding our mysterious Universe. 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."
The present concept, estimated to cost around 800 million euro, features as a baseline a 42-m diameter segmented mirror telescope housed in an 80-m diameter rotating dome. It incorporates a large internal mirror able to distort its own shape a thousand times per second. This 'Adaptive Optics' system will help to provide robust telescope operation even in case of significant wind turbulence and will largely overcome the fuzziness of stellar images due to atmospheric turbulence.
Professor Roger Davies, University of Oxford chairs ESO's ELT Standing Review Committee and serves on PPARC's Council. He said "The telescope design incorporates the crucial image sharpening technology in an innovative way that will give the 42m the full theoretical capability an instrument of that size can achieve. It will provide an unprecedented clear view of the distant universe enabling us to probe the origins of planets, stars and galaxies"
"The decision by the ESO Council to go ahead with the design study for a European Extremely Large Telescope is a very exciting one for European astronomy," said Professor Richard Wade, President of the ESO Council and Deputy CEO of the UK's science funding agency, the Particle Physics and Astronomy Research Council.
"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!"
Dr Isobel Hook of Oxford University led the team 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. 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 the new giant 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 mobilisation of European Institutes and high-tech Industries to develop critical enabling 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.
Professor Gerry Gilmore of the University of Cambridge chaired the design study leading up to this decision "Constructing an E-ELT is extremely challenging -- as you scale up a telescope the technical difficulties become much more significant. Scientists and industry will both have crucial parts to play in ensuring that the E-ELT is viable and the UK community will be looking to take leading roles in design and construction of the telescope and its instruments as well as in the eventual scientific work."
The primary 42-m diameter mirror is composed of 906 hexagonal segments, each 1.45 m in size, while the secondary mirror is as large as 6 m in diameter. In order to overcome the fuzziness of stellar images due to atmospheric turbulence the telescope needs to incorporate adaptive mirrors into its optics. A tertiary mirror, 4.2 m in diameter, relays the light to the adaptive optics system, composed of two mirrors: a 2.5-m mirror supported by 5000 or more actuators able to distort its own shape a thousand times per second, and one 2.7 m in diameter that allows for the final image corrections. This five mirror approach results in an exceptional image quality, with no significant aberrations in the field of view.
The site of the E-ELT is not yet fixed as studies are still undergoing with a plan to make a decision by 2008.
"The E-ELT will provide European astronomers with access to a facility that will allow them to do very exciting research projects including looking for Earth-like planets around other stars, a real quest for astronomers," said Richard Wade.
"This is really the beginning of a new era for optical and infrared astronomy," said Catherine Cesarsky.
Extremely Large Telescopes are considered world-wide as one of the highest priorities in ground-based astronomy. They will vastly advance astrophysical knowledge allowing detailed studies of, among others, planets around other stars, the first objects in the Universe, super-massive Black Holes, and the nature and distribution of the Dark Matter and Dark Energy which dominate the Universe. The European Extremely Large Telescope project will maintain and reinforce Europe's position at the forefront of astrophysical research, gained in large part at the turn of the Century through the ESO Very Large Telescope facility.
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