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Looking almost like an optical illusion, today’s Picture of the Week highlights why ESO’s Extremely Large Telescope (ELT) is called that. This image was taken inside the telescope’s dome, with some of the ELT’s team standing above the massive structure that will hold its main mirror. This 39-metre-diameter reflective surface will comprise 798 mirror segments that will work together as a single mirror, in what will be the biggest optical telescope on Earth.
This photo was taken when the ELT construction reached a momentous milestone. For the first time, the telescope’s structure was rotated around its vertical axis. ESO staff at the construction site, together with Ace/Cimolai’s team, who are leading the construction of the dome and main structure, rotated the telescope first by hand by a few centimetres, and then a full rotation using auxiliary motors. While this may seem small, the entire structure currently weighs around 3500 tonnes, which will further increase up to 4600 tonnes once the mirrors and science instruments are installed. The structure rests on a layer of oil just 80 microns thin that allows the telescope to rotate smoothly. Testing this motion is thus key to ensuring that this massive telescope can point at all areas of the southern sky.
“For me, this is a beautiful reminder of what can be achieved when people push in the same direction, literally and figuratively,” says Roberto Tamai, the ELT’s Programme Manager at ESO, shown on the right in this image. Marco Sciarra, Executive President of Cimolai, stands in the centre with Pascal Martinez, ESO Project Manager for the Dome and Main Structure, to the left.
The ELT, expected for first light later this decade, will be a gamechanger in astronomical research, as the world’s ‘biggest eye on the sky’. Besides its exceptional size, its cutting-edge instruments will allow us to understand our Universe better than ever before.
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Video of the ELT rotation test