A reddish laser beam is being launched from UT4 (Yepun) to create an artificial star at an altitude of 90 km in the Earth's mesosphere. This Laser Guide Star (LGS) is part of the Adaptive Optics system, which allows astronomers to remove the effects of atmospheric turbulence, producing images almost as sharp as if the telescope were in space. The bluish compact group of stars visible to the right of the laser beam is the Pleiades open cluster.
Yepun, which means Venus, and the other gigantic telescopes (Antu, Kueyen, Melipal) are located in the Atacama Desert of Chile.
