Before another clear, starry night falls at ESO's Paranal Observatory, home of the Very Large Telescope (VLT), the sky produces a palette of intense colours, putting on a beautiful show for observers. These colours can only be seen with such depth from sites such as Paranal, where the atmosphere is extraordinarily pure. Looking to the west, over the Pacific Ocean, the sunset sky turns bright orange and red. However, this photograph shows the view to the east instead, looking away from the Sun after it has just set. The grey-bluish shadow above the horizon is the shadow of our own planet. Above this is a pinkish glow known as the "Belt of Venus", a phenomenon produced by the reddened light of the setting Sun being backscattered by the Earth's atmosphere.
In the centre of the image is the fourth 8.2-metre Unit Telescope (UT4), part of the VLT. The Mapuche name given to UT4 is Yepun, which means Venus. As well as working as individual telescopes, groups of two or three UTs can combine their light using a technique called interferometry, which allows astronomers to see details up to 25 times finer than with the individual telescopes. The VLT also has four 1.8-metre Auxiliary Telescopes (ATs), housed in ultra-compact mobile enclosures, which are fully dedicated to interferometric observations. Two of the ATs are visible in the background, with a third mostly hidden.
The yellow frame-like structure in front of Yepun is the "M1 Lifting Platform", used when the giant 8.2-metre primary mirror (M1) of the telescope is periodically recoated. The delicate mirror and its support structure, which together weigh 45 tonnes, are removed from the telescope enclosure and slowly driven about two kilometres to a maintenance building at the Paranal base camp. This process is, unsurprisingly, performed with the utmost care.
Rolling red hills stretch out below the exceptionally clear blue sky that is typical of ESO's Paranal Observatory. Although the telescope domes close at dawn, and nothing seems to move on the surface of this barren desert, the ESO Very Large Telescope (VLT) never rests. Since early morning, a team of engineers and technicians has been working hard to prepare the telescopes and instruments for another "perfect night".
The 2600-metre-high Cerro Paranal stands out at the centre of this panoramic view, taken looking towards the south. This flattened mountaintop is home to the VLT, the world's most advanced ground-based optical and near infrared astronomical facility. The VLT has four 8.2-metre Unit Telescopes (UTs), plus four 1.8-metre Auxiliary Telescopes (ATs). In this picture, only two of the UT enclosures, together with the smaller 2.6-metre VLT Survey Telescope (VST) are visible.
To the right of Cerro Paranal, the sea of clouds that typically covers the coast of the Pacific Ocean — only 12 km away — is visible in the background. The cold oceanic stream typically keeps the thermal inversion layer of the atmosphere below an altitude of 1500 metres, making this remote area of the Chilean Atacama Desert in the II Region of Chile one of the driest sites on Earth and a perfect window on the Universe. The atmosphere here is extremely dry and clear, and has very low turbulence, offering the most suitable conditions for optical and near-infrared astronomical observations.
For this reason, the 3060-metre-high Cerro Armazones, located just some 20 km east of Paranal, was selected as the site for the future European Extremely Large Telescope (E-ELT). With a primary mirror 39 metres in diameter, the E-ELT will be the world's largest eye on the sky.
This photograph was taken from a neighbouring mountain, home of the 4.1-metre Visible and Infrared Survey Telescope for Astronomy (VISTA). VISTA started operations at the end of 2009 and is the most recent telescope to be added to the roster at ESO's Paranal Observatory. VISTA is the largest survey telescope in the world.