Duo in the Dark

Winter nights on the Chajnantor Plateau can seem incredibly isolating — but the wonder of some of the driest, darkest skies in the world is definitely something to be shared.

This image shows two of the 66 antennas that comprise the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, as they work together to observe the skies in millimetre and submillimetre wavelengths. These wavelengths are notoriously difficult to observe, as water vapour in the atmosphere absorbs this kind of light and prevents it from reaching the ground. To catch sight of it, telescopes must be placed at very high altitudes where the air is drier and less absorbent. For ALMA, that means an elevation of 5000 metres.

Hanging above the pair of telescopes is the constellation of Orion (The Hunter), identifiable by his distinctive star-studded belt. His shoulder is marked by the red supergiant Betelgeuse, on the right of the photo, located just under 650 light-years away from us. Betelgeuse is a prime target for observations in millimetre and submillimetre wavelengths, as is the neighbouring Orion Nebula.