Go big or go home
At the end of April, the European Southern Observatory culminated a multi-year site selection process for construction of the world’s largest telescope. Known as the E-ELT for the European Extremely Large Telescope, it will have a primary mirror spanning 138 feet. That size is more than four times larger than the biggest single-aperture telescope operating today. On the short list of candidate sites were four locations in Chile and one in the Canary Islands, Spain.
After extensive study, the ESO council selected a peak named Cerro Armazones on the high plateau of Chile’s Atacama desert. With an elevation about 10,000 feet above sea level, conditions at Cerro Armazones will maximize the benefits of a yearly average of 350 cloud-free nights, low water vapor (important for infra-red studies), and a steady atmosphere.
South America has long been a favored location for both European and American astronomers dating back to the 1890’s and the Harvard College Observatory’s pioneering photographic survey of the southern night skies. Certainly there are few sure things in life, but the super-sized challenge of the E-ELT, not to mention a billion dollar-plus price tag, makes Cerro Armazones the safest bet.
Everything about the E-ELT is king-sized. When completed, it will be the monster truck of observational astronomy. The primary mirror will consist of 984 hexagonal panels, each one over 4.5 feet wide. The diameter of the secondary mirror alone will be larger than the famous 200-inch Hale telescope atop Palomar Mountain, itself the holder of the world’s largest telescope title for 45 years.
In addition to its two main mirrors, the E-ELT will have three other mirrors offering image-enhancing abilities by eliminating the effects of atmospheric turbulence and wind. The E-ELT will collect over 15 times the light and far surpass the resolution any of today’s telescopes including the Hubble Space Telescope.
Science objectives for the E-ELT include: direct imaging of rocky planets outside our solar system, gathering evidence to help us understand the formation and evolution of galaxies, learning about the role of black holes in shaping the structure of the Universe, peering into the Universe’s ‘Dark Ages’ – the era before the first stars formed, and perhaps the most intriguing, to directly measure the rate of universal expansion.
All of the candidate sites were equal in many respects. The factors that tilted the choice toward Cerro Armazones were the proximity of ESO’s observatory at Cerro Paranal, the Chilean government’s donation of land and aggressive stance on minimizing the adverse impacts of mining operations and light pollution.
If all goes as planned, the E-ELT will see first light in 2018. For all of my years stargazing, I have been itching for an excuse to get to the southern hemisphere. I know it will take at least eight more years for me to save up enough money to make the trip. I’m going to need a pretty big coin jar!
