ESO (European southern Observatory) is to build the largest optical/infrared telescope in the world. At its meeting in Garching today, the ESO Council approved the European Extremely Large Telescope (E-ELT) Programme, pending confirmation of four so-called ad referendum votes. The E-ELT will start operations early in the next decade.
The E-ELT will collect 100 million times more light than the human eye and 8 million times more the telescope that Galileo used.
With the start of operations planned for early in the next decade, 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.
With its main mirror as large as 39.3 metres 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 telescopes in planning, the Thirty-Meter Telescope and the Giant Magellan Telescope.
Almost 1000 segments
It is not possible, nor advised, to build such a large mirror in one piece. Instead, the 39.3-metre diameter primary 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.
A new architectural concept drawing of ESO’s planned European Extremely Large Telescope (E-ELT) shows the telescope at work, with its dome open and its record-setting 40-metre-class primary mirror pointed to the sky. In this illustration, clouds float over the valley overlooked by the E-ELT’s summit. The comparatively tiny pickup truck parked at the base of the E-ELT helps to give a sense of the scale of this massive telescope. The E-ELT dome will be similar in size to a football stadium, with a diameter at its base of over 100 meters and a height of over 80 meters.