Green Airglow and Auxiliary Telescopes

Night sky above Cerro Paranal observatory in the Atacama Desert, Chile. From the photographer: “In the foreground are three of the four movable Auxiliary Telescopes, each 1.8 meters in diameter, a part of the VLT array. Also visible in the starry sky is strong green airglow.”

The Very Large Telescope (VLT) is an array of optical telescopes operated by ESO, the European Southern Observatory. It consists of four telescopes with main mirrors of 8.2m diameter, which are generally used separately but can be used together to achieve very high angular resolution, allowing astronomers to see details up to 25 times finer than with the individual telescopes. The VLT interferometer can reconstruct images with an angular resolution of milliarcseconds, equivalent to distinguishing the two headlights of a car at Moon distance.