File:Growing every day (potw2439a).jpg

English: Just like the Sun, ESO’s Extremely Large Telescope (ELT) is rising in Cerro Armazones, Chile. With this Picture of the Week, you have the chance to enjoy a spectacular sunrise over the largest optical telescope in the world.See the dark spots on the Sun’s surface? In these huge areas, easily the size of a planet, the temperature is lower than on the rest of the Sun’s surface. They can last anywhere from a few days to a few months. The amount of sunspots depends on solar activity, increasing and decreasing in a cycle of around 11 years. A peak is expected in 2025.Here, the Sun is lighting up the ELT construction site, almost like a shadow theatre. The steel dome, in which the telescope will be encased to protect it from the harsh desert weather, is steadily taking shape. Compare this view with the snapshot taken last year and you’ll see just how much progress has been made on the cladding of the dome. Once it’s finished, more than 600 giant pieces of thermally insulated aluminium will be covering the structure. And it’s not just its size that is impressive: the upper part of this colossal construction can rotate 360 degrees!While you can’t see it here, the structure that will hold the ELT’s 39-m mirror is also taking shape at a steadfast pace, as is the mirror itself. The ELT is set to open its gigantic eye for the first time later this decade, and scientists are in for some revolutionary discoveries. We can’t wait!