Star circles and the VLT

This long-exposure image from ESO Photo Ambassador F. Kamphues shows the 4 Laser Guide Star Facility on ESO's Very Large Telescope (VLT) tracking an object throughout an observation. The lasers are an integral part of the adaptive optics system on the VLT, and allow astronomers to vastly reduce the atmospheric distortion present at even the best sites in the world for astronomy, including Paranal in Chile, the home of the VLT.

The guide stars can be seen to track a specific patch of sky, tracing an arc across the Chilean sky.