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World’s Biggest Telescope to be Located on Armazones, Chile

Night-time panorama showing Cerro Armazones in the Chilean desert, near ESO's Paranal Observatory, site of the Very Large Telescope (VLT)
The planned European Extremely Large Telescope will sit atop Cerro Armazones in the Chilean desert.
ESO/S. Brunier

The ESO Council has selected Cerro Armazones as the baseline site for the planned 42-meter European Extremely Large Telescope (E-ELT). Cerro Armazones is a mountain at an altitude of 3060 meters in the central part of Chile’s Atacama Desert, some 130 kilometers south of the town of Antofagasta and about 20 kilometers from Cerro Paranal, home of ESO’s Very Large Telescope.

“This is an important milestone that allows us to finalise the baseline design of this very ambitious project, which will vastly advance astronomical knowledge,” says Tim de Zeeuw, ESO’s Director General. “I thank the site selection team for the tremendous work they have done over the past few years.”

ESO’s next step is to build a European extremely large optical/infrared telescope with a primary mirror 42 meters in diameter. The E-ELT will be “the world’s biggest eye on the sky” — the only such telescope in the world. ESO is drawing up detailed construction plans together with the community. The E-ELT will address many of the most pressing unsolved questions in astronomy, and may, eventually, revolutionize our perception of the Universe, much as Galileo’s telescope did 400 years ago. The final go-ahead for construction is expected at the end of 2010, with the start of operations planned for 2018.

The decision on the E-ELT site was taken by the ESO Council, which is the governing body of the Organisation composed of representatives of ESO’s fourteen Member States, and is based on an extensive comparative meteorological investigation, which lasted several years. The majority of the data collected during the site selection campaigns will be made public in the course of the year 2010.

Various factors needed to be considered in the site selection process. Obviously the “astronomical quality” of the atmosphere, for instance, the number of clear nights, the amount of water vapor, and the “stability” of the atmosphere (also known as seeing) played a crucial role. But other parameters had to be taken into account as well, such as the costs of construction and operations, and the operational and scientific synergy with other major facilities (VLT/VLTI, VISTA, VST, ALMA, and SKA etc).

In March 2010, the ESO Council was provided with a preliminary report with the main conclusions from the E-ELT Site Selection Advisory Committee.

These conclusions confirmed that all the sites examined in the final shortlist (Armazones, Ventarrones, Tolonchar, and Vizcachas in Chile, and La Palma in Spain) have very good conditions for astronomical observing, each one with its particular strengths. The technical report concluded that Cerro Armazones, near Paranal, stands out as the clearly preferred site, because it has the best balance of sky quality for all the factors considered and can be operated in an integrated fashion with ESO’s Paranal Observatory. Cerro Armazones and Paranal share the same ideal conditions for astronomical observations. In particular, over 320 nights are clear per year.

Taking into account the very clear recommendation of the Site Selection Advisory Committee and all other relevant aspects, especially the scientific quality of the site, Council has now endorsed the choice of Cerro Armazones as the E-ELT baseline site.

“Adding the transformational scientific capabilities of the E-ELT to the already tremendously powerful integrated VLT observatory guarantees the long-term future of Paranal as the most advanced optical/infrared observatory in the world and further strengthens ESO’s position as the world-leading organization for ground-based astronomy,” says de Zeeuw.

In anticipation of the choice of Cerro Armazones as the future site of the E-ELT and to facilitate and support the project, the Chilean Government has agreed to donate to ESO a substantial tract of land contiguous to ESO’s Paranal property and containing Armazones in order to ensure the continued protection of the site against all adverse influences, in particular light pollution and mining activities.

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organization in Europe and the world’s most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland, and the United Kingdom. ESO carries out an ambitious program focused on the design, construction, and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organizing cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal, and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and VISTA, the world’s largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence.

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