A watercolour sky

The Atacama Desert in Chile is one of the darkest and most peaceful astronomical sites on Earth — and has, as a result, proven to be the perfect location for ESO’s various observatories and powerful instruments. 

This view shows ESO’s Paranal Observatory, home to the behemoth Very Large Telescope (VLT). The constituent telescopes of the VLT can be seen standing sentinel beneath a star-studded sky featuring the glittering arch of our Galaxy, and the glowing Magellanic Clouds (left). As this image demonstrates, the sky over Paranal isn’t completely dark; after sunset, the beauty of the Universe is overshadowed by that of Earth’s own atmosphere, which glows in multiple hues and paints the sky like a watercolour. The playful brushstrokes of the faraway emission nebulae that adorn the Milky Way and the constellation of Orion (The Hunter) in the upper centre of the frame, are joined by the soft swaths of green, yellow, red, and orange lying close to the horizon.

This colourful palette is airglow — atmospheric radiance caused by chemical processes that occur up to about a few hundred kilometres above ground. Just after the Sun has set in the west (centre), its strong light also reflects from specks of rock and ice sitting between it and us, causing them to glimmer and show up as a diffuse white ray (lower centre).