The VLT's Laser Guide Star Facility

In this timelapse video, we see the four lasers attached to Yepun, one of the four telescopes making up ESO's Very Large Telescope, beaming up high into the atmosphere. There they excite atoms of sodium, producing a bright spot known as an artificial star. Astronomers use this artificial star to track the turbulence in the atmosphere that causes images of celestial objects to become blurred. They then adjust a flexible mirror within the telescope's adaptive optics systems to compensate for the blurring and so produce much sharper images.