Astronomy is experiencing a golden era. The past decade alone has brought amazing discoveries that have excited people from all walks of life, from the first planets orbiting other stars to the accelerating Universe, dominated by the still-enigmatic dark matter and dark energy. Europe is at the forefront of all areas of contemporary astronomy, thanks in particular to the flagship ground-based facilities operated by ESO, the pre-eminent intergovernmental science and technology organisation in astronomy. The challenge is to consolidate and strengthen this position for the future.
This will be achieved with a revolutionary new ground-based telescope concept, the European Extremely Large Telescope (E-ELT), with a performance that is orders of magnitude better than currently existing facilities. Such a telescope may, eventually, revolutionise our perception of the Universe, much as Galileo's telescope did, 400 years ago. The European Extremely Large Telescope, with a proposed diameter of 42 metres, is currently undergoing a very detailed design phase. The go-ahead for E-ELT construction is planned for late 2010, with start of operations planned for the end of the decade.
The telescope's "eye" will be almost half the length of a soccer pitch in diameter and will gather 15 times more light than the largest optical telescopes operating today. The telescope has an innovative five-mirror design that includes advanced adaptive optics to correct for the turbulent atmosphere, giving exceptional image quality. The main mirror will be made up from almost 1000 hexagonal segments.
This series of artist’s impressions shows some of the main phases in the early stages of construction of the European Extremely Large Telescope (E-ELT), assuming the final go-ahead is given at the end of 2010. The E-ELT is to be built on Cerro Armazones, a 3060-metre high mountain near ESO’s Paranal Observatory in Chile, and is planned to be operational in 2018.
With a primary mirror 42 metres across, far larger than any visible light telescope currently in operation, the E-ELT will be “the world’s biggest eye on the sky”. This will give it an unparalleled power to see faint and distant objects in the sky.
The E-ELT will tackle the biggest scientific challenges of our time, and aim for a number of notable firsts, including tracking down Earth-like planets around other stars in the habitable zones where life could exist — one of the Holy Grails of modern observational astronomy. It will also perform “stellar archaeology” in nearby galaxies, as well as make fundamental contributions to cosmology by measuring the properties of the first stars and galaxies and probing the nature of dark matter and dark energy. On top of this astronomers are also planning for the unexpected — new and unforeseeable questions will surely arise from the new discoveries made with the E-ELT. The E-ELT may, eventually, revolutionise our perception of the Universe, much as Galileo’s telescope did, 400 years ago.
Erecting the E-ELT’s housing is a major engineering feat. Because of the size of the equipment inside, the moveable dome of the building has to be over 80 m high — about the height of the dome of St Paul’s Cathedral in London.
The present core concept is for a telescope with a mirror 42 metres in diameter, covering a field on the sky about a tenth the size of the full Moon. The mirror design itself is revolutionary and is based on a novel five-mirror scheme that results in an exceptional image quality. The primary mirror consists of almost 1000 segments, each 1.4 metres wide, but only 50 mm thick. The optical design calls for an immense secondary mirror 6 metres in diameter, almost as large as the biggest primary telescope mirrors in operation today.
42 metre diameter ....... With its main mirror as large as 42 metre in diameter, this will be the largest telescope to observe in visible-light. It will be four to five times larger than the present-day state-of-the-art facilities of this kind, and will collect about 15 times more light. It will also be much larger than the two other extremely large telescope in planning, the Thirty-Meter Telescope and the Giant Magellan Telescope.
The arch of the Milky Way is photographed over Cerro Armazones; a 3064m high mountain located in the Chilean Coast Range. Because it is dark, has steady atmospheric condition (good seeing), and it receives almost 350 cloudless in a year, it is selected by the European Southern Observatory as the site for the planned European Extremely Large Telescope (EELT). By 2018 there will be a nearly 30-story-high dome on this location which will house the giant telescope. It will be the world's largest telescope with aperture of 42 meters; four times the diameter of the current largest optical telescopes. As recorded in this photo the atmospheric conditions above the site are monitored by researchers now.
Almost 1000 segments ............. It is not possible, nor advised, to build such a large mirror in one piece. Instead, the 42-m mirror will be composed of about 1000 hexagonal segments, about 1.4 metre wide and 5 cm thick. The whole concept of the telescope is in fact to be modular, so that pieces can be manufactured in large quantities, thereby drastically reducing the cost. Only this approach makes the E-ELT possible within a restricted budget.