November – Yepun’s laser beam

One of the four Unit Telescopes that make up ESO’s Very Large Telescope (VLT) at Paranal in Chile, this telescope is named Yepun, which means Venus in the Mapuche language of southern Chile. Beneath the Milky Way, the Laser Guide Star Facility mounted on Yepun is seen here in action. The laser beam’s colour is precisely tuned to energise a layer of sodium atoms in the atmosphere so as to create a small bright spot. This artificial star is used as a reference to work out how much the atmosphere is distorting the light from actual stars — a process called adaptive optics, which helps Yepun produce sharp images.


ESO/Y. Beletsky

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