When Light Collides

This Picture of the Week captures the skies above ESO’s Paranal Observatory ablaze with colour — blues, purples, oranges, greens, yellows and reds all mingle together to create this striking view of the Chilean site. One of the Auxiliary Telescopes (ATs) comprising ESO’s Very Large Telescope (VLT) is visible in the foreground, bathed in an eerie yellow-green glow. 

This AT is just one of the VLT’s four 1.8-metre auxiliaries, which also includes four giant 8.2-metre cousins (Unit Telescopes).The ATs are unique; they are self-contained and, depending on the needs of the observing project, can be repositioned in up to 30 different observing locations along a system of tracks. Acting together as the VLT Interferometer (VLTI), they capture light from celestial objects and send it to the same focal point through a system of mirrors housed within underground tunnels, allowing researchers to observe the cosmos in incredible detail. 

Comprising eight telescopes in total, the VLT is the world’s most advanced visible-light astronomical observatory. Its magnificent resolution makes it possible to see fine detail on the surface of a star, and even to study the surroundings of a black hole.