Lasers in the sky

ESO's Very Large Telescope (VLT) counteracts the blurriness of stars caused by the atmosphere through use of the 4 Laser Guide Star Facility (4LGSF). The 4LGSF 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. These stars act as reference points to artificially remove the twinkling of stars.