The European Southern Observatory (ESO) Council has selected Cerro Armazones as the baseline site for the planned 42-m European Extremely Large Telescope (E-ELT). Cerro Armazones is a mountain at an altitude of 3060 m in the central part of Chile's Atacama Desert, some 130 km south of the town of Antofagasta and about 20 km from Cerro Paranal, home of the ESO’s Very Large Telescope. “This is an important milestone that allows us to finalize the baseline design of this very ambitious project, which will vastly advance astronomical knowledge,” said 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.” Cerro Armazones – in the Chilean desert, near the Paranal Observatory – was chosen as the site for the planned European Extremely Large Telescope (E-ELT). With a 42-m-diameter mirror, the E-ELT will be the world’s biggest eye on the sky. Cerro Armazones also is the home of the Very Large Telescope. (Image: European Southern Observatory/S. Brunier) ESO’s next step is to build an E-ELT with a primary mirror 42 m 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 organization composed of representatives of ESO’s 14 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, more than 320 clear nights 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, the council 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 the 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,” de Zeeuw said. 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. For more information, visit: www.eso.org