Beam me up, Yepun

The glowing beams of the 4 Laser Guide Star Facility (4LGSF) dominate this eye-catching image from ESO Photo Ambassador Petr Horálek.

The 4LGSF, installed on Unit Telescope 4 — also known as Yepun — sends four laser beams into the skies to produce four artificial stars by exciting sodium atoms located in the atmosphere at an altitude of 90 kilometres. Each laser delivers 22 watts of power — about 4000 times the maximum allowed for a laser pointer — in a beam with a diameter of 30 centimetres.