The night sky in the evening twilight above Cerro Armazones in the Atacama Desert, Chile. Bright stars Alpha and Beta centauri are above the horizon in the middle. The Southern Cross (constellation Crux) and the Coalsack dark nebula appear above them. The foreground mountaintop is Cerro Armazones, in the Antofagasta Region of Chile, the site for the European Extremely Large Telescope (E-ELT), an optical/infrared telescope with a 39.3 m diameter primary mirror, the largest on Earth. It should be operational in the early 2020s.