A very large guide star

Four lasers beam out from one of the Unit Telescopes of ESO's Very Large Telescope (VLT), guiding your eyes to the Small and Large Magellanic Clouds beneath them.

The Four Laser Guide Star Facility (4LGSF) shines four 22-watt laser beams into the sky to create artificial guide stars by making sodium atoms in the upper atmosphere glow so that they look just like real stars. The artificial stars allow the adaptive optics systems to compensate for the blurring caused by the Earth’s atmosphere and so that the telescope can create sharp images.