August — A laser show on Paranal

This picture was taken using a long exposure at ESO’s Paranal Observatory in the Chilean Atacama Desert. Above the mountaintop observatory, a spectacular dance is playing out: imaged over several hours, stars appear to make their way in long arcs, called star trails, across the night sky. 

Paranal is home to one of the world’s most advanced optical telescopes: ESO’s Very Large Telescope, or VLT. This flagship facility actually consists of four Unit Telescopes and four smaller movable Auxiliary Telescopes, like the one in the foreground on the right.

The Four Laser Guide Star Facility propagates laser beams into the sky, making sodium atoms in the upper atmosphere glow like artificial stars. The twinkling of these artificial stars is measured in real time and used by the adaptive optics system to correct for the blurring caused by the Earth’s atmosphere so that the telescope can create sharp images.

The original image can be downloaded in high resolution on https://www.eso.org/public/images/potw2339a/