The Extremely Large Telescope (ELT) under construction in Chile’s Atacama Desert will be the world’s biggest optical telescope when completed in 2028. With a giant 39.3-meter main mirror and advanced adaptive optics, the ELT will collect far more light and achieve much sharper images than any existing ground-based telescope, revolutionizing the study of exoplanets, black holes, dark matter, and the early universe. Economist adds: But when it comes to detecting the dimmest and most distant objects, there is no substitute for sheer light-gathering size. On that front the ELT looks like being the final word for the foreseeable future. A planned successor, the “Overwhelmingly Large Telescope,” would have sported a 100-metre mirror. But it was shelved in the 2000s on grounds of complexity and cost. The Giant Magellan Telescope is currently being built several hundred kilometres south of the elt on land owned by the Carnegie Institution for Science, an American non-profit, and is due to see its first light some time in the 2030s. It will combine seven big mirrors into one giant one with an effective diameter of 25.4 metres. Even so, it will have only around a third the light-gathering capacity of the ELT.
A consortium of scientists from America, Canada, India and Japan, meanwhile, has been trying to build a mega-telescope on Hawaii. The Thirty Meter Telescope would, as its name suggests, be a giant — though still smaller than the elt. But it is unclear when, or even if, it will be finished. Construction has been halted by arguments about Mauna Kea, the mountain on which it is to be built, which is seen as sacred by some. For the next several decades, it seems, anyone wanting access to the biggest telescope money can buy will have to make their way to northern Chile.
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