Mountaintop majesty

ESO/P. Horálek

The sweeping river of stars that is the Milky Way ribbons over Cerro Paranal in Chile, home to the European Southern Observatory’s Very Large Telescope (on the peak to the left) and the Visible and Infrared Survey Telescope for Astronomy, VISTA (on the peak to the far right).

Between the two peaks is a brilliant, blazing orb, but appearances are deceiving. This is not a shining light on the mountainside, but the planet Jupiter, photographed just at the moment that it rises over the landscape. On the far left is another galaxy entirely – the Large Magellanic Cloud.

The Very Large Telescope is a huge, multi-telescope observatory in its own right. Its main instruments are the four large Unit Telescopes, each with a mirror 8.2 metres in diameter. Named Antu, Kueyen, Melipal and Yepun, referring to astronomical names in the local Mapuche language, the Unit Telescopes can operate either individually or together as a vast interferometer, often in unison with four other, smaller telescopes that are on site. These are the 1.8-metre auxiliary telescopes, which move on tracks to change the shape of the collecting area to suit whichever target is being observed.

VISTA, meanwhile, is a near-infrared optimised telescope constructed by British institutions as part of the UK’s membership agreement into the European Southern Observatory. Sporting a 4.1-metre mirror, VISTA is the largest infrared survey telescope in the world and has just a single instrument, the VISTA Infrared Camera (VIRCAM), but this coming year a new instrument called 4MOST – 4-metre Multi- Object Spectroscopic Telescope – will be added to VISTA. Using optical fibres movable by robotic actuators, it will be capable of simultaneously taking spectra from 2,400 objects in the field of view, be they stars, galaxies or large nebulous regions. Image: ESO/P. Horálek.