The ESO Turns Its Massive Laser Beam on the Heavens

Snapped at the European Southern Observatory's Paranal Observatory -- home of the Very Large Telescope (VLT) array -- the photo depicts the VLT's Laser Guide Star facility in action.

The laser beam is part of the VLT's adaptive optics system, which corrects for distortions caused by Earth's atmosphere so the land-based optics system can get clear shots of the cosmos. In this case, the color of the laser is precisely tuned to excite a band of sodium atoms found in an upper layer of the atmosphere some 56 miles up. Those glowing atoms create a kind of synthetic reference star in the upper atmosphere that the VLT can use to calibrate itself.

via ESO