The European Extremely Large Telescope

Extremely Large Telescopes are considered worldwide as one of the highest priorities in ground-based astronomy. They will vastly advance astrophysical knowledge, allowing detailed studies of subjects including 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.

Since the end of 2005 ESO has been working together with its user community of European astronomers and astrophysicists to define the new giant telescope needed by the middle of the next decade. More than 100 astronomers from all European countries have been involved throughout 2006, helping the ESO Project Offices to produce a novel concept, in which performance, cost, schedule and risk were carefully evaluated.
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.

Adaptive mirrors are incorporated into the optics of the telescope to compensate for the fuzziness in the stellar images introduced by atmospheric turbulence. One of these mirrors is supported by more than 5000 actuators that can distort its shape a thousand times per second.The telescope will have several science instruments. It will be possible to switch from one instrument to another within minutes. The telescope and dome will also be able to change positions on the sky and start a new observation in a very short time.
The ability to observe over a wide range of wavelengths from the optical to mid-infrared will allow scientists to exploit the telescope's size to the fullest extent.

With the start of operations planned for 2018, 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.