The world’s largest optical telescope, equipped with a primary mirror that stretches nearly 40 meters (130 feet) across, is currently taking shape in a high, dry region of the Chilean desert. Appropriately named the Extremely Large Telescope (ELT), the observatory will be able to spot Earth-sized planets in other star systems, peer into the dark reaches of the early cosmos, and help clock the acceleration of the universe’s expansion.
“We always talk about telescopes in terms of the size of their main mirror, and ours is 39 meters, which makes it five times, in diameter, bigger than the present biggest telescopes that we run,” said Suzanne Ramsay, ELT instrument manager, in the latest episode of Motherboard’s Space Show. “So, indeed, Extremely Large is very well named—if not very imaginatively named.”
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“In terms of dimensions, it’s as big as the Coliseum in Rome,” added Michele Cirasuolo, ELT programme scientist. “So you are building a huge cathedral, but at the same time, that huge cathedral has to move, and maintain the quality of optics to nanometer accuracy.”
The construction of such a complex and precise observatory is a major feat that leverages the talent of an international collaboration of scientists and engineers under the banner of the European Southern Observatory. If all goes to plan, the hard work will pay off around 2027, when the ELT is expected to open its enormous eye on the sky.
The year 2027 “seems far away,” Cirasuolo said, “but for us, it’s tomorrow morning.”
Watch the episode to learn more about the unprecedented design of the telescope, its ability to search for potentially habitable exoplanets, and the new insights it will reveal about the origins of stars and galaxies.
