Photo de la semaine

29 juillet 2024: This Picture of the Week takes you all the way to ESO’s Paranal Observatory in the Chilean Atacama Desert, to enjoy a spectacular sunset next to the Very Large Telescope (VLT). But that’s not the only wonder displayed by the clear skies of the Atacama. See that blueish glow across the sky? The zodiacal light — also called “false dawn” when seen before sunrise — is a faint, diffuse band of light in the night sky, reaching up from the horizon. It follows the direction of the ecliptic — the plane of Earth's orbit around the Sun. This plane is rich in tiny particles of dust, which scatter sunlight and create this phenomenon. The other planets in the Solar System orbit the Sun in roughly the same plane, and therefore can be often seen within the zodiacal light. In this particular image, Venus is the brightest source and Mars is ...

22 juillet 2024: Did you know that ESO’s Extremely Large Telescope (ELT) will have a primary mirror (M1) that weighs 200 tonnes, about as much as the largest blue whales? This colossal mirror will rest on the structure that is shown under construction in this Picture of the Week, taken with a drone on July 2024. M1 will be the largest segmented mirror ever built for a telescope, but will need to move constantly and very smoothly during observations while keeping its optical shape, and therefore needs to be held by a cell that is both lightweight and sturdy. Enter the throne that will eventually seat this segmented mirror: the M1 cell seen here. It will hold 798 hexagonal segments that will work together as a single 39-m mirror, staying aligned as the telescope moves, even under varying gravity loads, wind conditions, vibrations or changes in temperature. German company SCHOTT has cast and ...

15 juillet 2024: This Picture of the Week shows the distant galaxy PJ0116-24, a so-called Hyper Luminous Infrared Galaxy (HyLIRG). HyLIRGs are incredibly bright galaxies, lit up by the extremely rapid star formation within them. But what triggers this? Previous studies suggested that such extreme galaxies must result from galaxy mergers. These galaxy collisions are thought to create dense gas regions in which rapid star formation is triggered. But isolated galaxies could also become HyLIRGs via internal processes alone, if star-forming gas is rapidly funneled towards the galaxy’s centre. In a new paper led by Daizhong Liu (Max-Planck Institute for Extraterrestrial Physics), observations from ESO’s Very Large Telescope (VLT) and the Atacama Large Millimetre/submillimetre Array (ALMA) were combined to study the motion of gas within PJ0116-24. ALMA traces cold gas, seen here in blue, whereas the VLT, with its new Enhanced Resolution Imager and Spectrograph (ERIS), traces warm gas, shown in red. Thanks ...

8 juillet 2024: ESO’s La Silla Observatory is located on the outskirts of the Chilean Atacama Desert, 600 km north of Santiago de Chile and at an altitude of 2400 metres. As ESO’s first observatory, it has been seeing wonders in the night sky ever since it started operations in the 1960s, but sometimes it also gets to see wonderful things right at its doorstep. The Atacama Desert is the driest place on Earth outside the polar regions in terms of average rainfall. But when rain does fall, complemented by the right temperature and sunlight, it can trigger something spectacular: over 200 different plant species, whose seeds and bulbs lie dormant in the ground during the dry periods, start to bloom. Soon, hundreds of kilometres of otherwise sandy, rocky, and barren desert are covered in purple, pink, and yellow flowers — a phenomenon called “desierto florido” (the flowering desert). Since the weather ...

1 juillet 2024: Over a hundred kilometres from the nearest town, sat in the lonely hills of Cerro Armazones in the dry Chilean desert, the site of the Extremely Large Telescope (ELT) is thrumming with activity as the telescope continues a dedicated march of progress. This drone footage shows off the ELT’s recent strides, including the insulating cladding being used to dress the dome and the white lattice structure at the centre — now almost complete — that will support the ELT’s 39-m primary mirror. Around the 1:30 mark, we can also see two arc-shaped tracks, currently protected with tan wooden plates, bracketing the white lattice. These tracks will allow the telescope to move in altitude. The grey beams at opposite sides of the lattice, seen more clearly at the 2:15 mark, will support the so-called Nasmyth platforms — two tennis-court-sized areas where the scientific instruments will rest. Seeing this extraordinary stature against ...

24 juin 2024: Around 11 000 years ago a massive star ended its life in a powerful explosion, known as a supernova. During explosions like this, shock waves ripple out through the surrounding gas, compressing it into intricate thread-like structures. The energy that’s released during a supernova then heats these threads, causing them to shine brightly. The result is what we can see in this Picture of the Week: the Vela supernova remnant. This picture is just a small chunk of a much larger image, taken with the OmegaCAM instrument on the VLT Survey Telescope (VST), which is hosted at ESO’s Paranal Observatory. At only 800 light-years from Earth, the Vela supernova remnant is one of the closest examples of these dramatic events. Thanks to its proximity we can study this object in great detail, to help us understand what happens when massive stars reach the end of their life in spectacular fashion.

17 juin 2024: This picture of the week shows six of ALMA’s sixty-six antennas, located on the Chajnantor Plateau in the Chilean Atacama desert. But why are they pointed at the Sun? This photograph was taken in March 2023 after a snowfall, and some snow had accumulated on the antennas. Aiming them at the Sun helps to thaw the snow. The Atacama Large Millimetre/submillimetre Array (ALMA) observes radiation from the coldest objects in the Universe. By observing this light, emitted often by the vast, frigid gas clouds out of which stars and galaxies form, ALMA is able to see the Universe in its earliest eras and aims to uncover our cosmic origins. ALMA is operated by ESO together with international partners.

10 juin 2024: This Picture of the Week shows the brightly coloured Gum 3 nebula as seen with the VLT Survey Telescope (VST), hosted at ESO’s Paranal Observatory in the Chilean Atacama Desert. Attentive viewers may find that part of Gum 3 resembles a Koi fish in this VST image. Equipped with the OmegaCAM instrument, an enormous 268-megapixel camera, the telescope is designed to survey large areas of the southern sky in visible light and take stunning images like this one. Gum 3 is an interstellar cloud of gas and dust located about 3600 light-years away, between the Monoceros and Canis Major constellations. It is named after Colin Stanley Gum, an Australian astronomer who catalogued 84 nebulae in the southern sky. When the intense ultraviolet radiation from nearby young stars hits hydrogen atoms in the cloud, they emit visible light at very specific colours, which we see as shades of red and pink ...

3 juin 2024: Is it a comet? Is it a spaceship? The object in this Picture of the Week might be a bit hard to recognise at first. It is in fact a young star — but why does it have such an unusual shape? Young stars are surrounded by a disc of gas and dust: the building materials for planets. When other very bright and massive stars are present nearby, their light heats the young star’s disc, stripping away part of its material. The teardrop-shaped object in this image, 177-341 W, is in the Orion Nebula. The stars eroding away the disc of 177-341 W are out of the frame past the upper-right corner; when their radiation clashes with the material around the young star, it creates the bright, bow-like structure seen here in yellow. The tail extending from the star towards the lower-left corner is material being dragged away from 177-341 ...

27 mai 2024: Stay very still — in this Picture of the Week, we have encountered a wild pack of ALMA antennas huddled for warmth in their natural habitat: the Chajnantor Plateau in Chile. This unique species of telescope lives at an incredible altitude above 5000 metres, making it one of the highest sites for astronomical observations on Earth. The 66 antennas of the Atacama Large Millimetre/submillimetre Array (ALMA) watch the sky day and night for incoming light at wavelengths around a millimetre. This selective eyesight observes some of the coldest objects of the cosmos, from the bleak clouds of gas and dust between stars to the far-off galaxies of the early Universe. Light at millimetre wavelengths is easily absorbed by water vapour in the Earth’s atmosphere, but the immensely dry climate of the Chajnantor Plateau is ideally suited to get the best possible observations. ALMA — in which ESO is a partner ...

20 mai 2024: Growing is hard work — and this Picture of the Week, taken on 3 April 2024, shows ESO’s Extremely Large Telescope (ELT) taking a well-deserved night-time rest. The view from inside the telescope’s dome shows progress on this giant structure, 80 metres high and 88 metres wide, which will protect the world’s biggest eye on the sky from the extreme environment of Chile’s Atacama Desert. The dome’s steel skeleton is complete, and now a protective insulated cladding — the dark blue panels seen above — is being applied over it. This cladding consists of different layers, including thermal insulation and aluminium sheets outside. Together with air conditioning — active during the day, when the dome is closed —, this will keep the air inside the dome at the same temperature as the outside environment, minimising turbulence that could otherwise blur the images the ELT will capture. In the centre, on ...

13 mai 2024: This Picture of the Week shows Gum 46, a stunning gas cloud 5500 light-years away, observed in brand new detail with ESO’s Very Large Telescope (VLT). But why does it glow pink? At the heart of Gum 46 there’s a young, hot and blue star called HD311999. Its intense radiation excites atoms in the surrounding gas, which then re-emit this energy at very specific colours or wavelengths. The pink shade that dominates this image is due to hydrogen atoms, the most abundant element in this nebula and the Universe as a whole. The dark wispy clouds that surround the nebula make for a stunning sight too. These clouds are not intrinsically dark: they are extremely dense regions of dust that block light passing through them, enshrouding the glowing heart of Gum 46. This image was created as part of the ESO Cosmic Gems programme, an outreach initiative to produce images ...

6 mai 2024: This photo shows the buildings of the ALMA Array Operations Site in the Chilean Atacama Desert surrounded by snow. Wait a minute — there’s snow in the desert? The Atacama Desert is one of the driest places in the world — more specifically, the driest place on Earth outside the polar regions in terms of average rainfall. The very low levels of water vapour in the atmosphere and the almost constantly clear skies make it an ideal location for astronomical observations. However, as this photo from August 2023 — wintertime in Chile — shows, snow can occasionally visit the desert. The Atacama Large Millimeter/sub-millimeter Array (ALMA), in which ESO is a partner, is one of the largest astronomical projects in the world. The telescope’s 66 radio antennas are located at the Array Operations Site (AOS) on Llano de Chajnantor, an impressive 5000 metres above sea level and about 40 km ...

29 avril 2024: The three BlackGEM telescopes seen at the centre of this Picture of the Week, hosted at ESO’s La Silla Observatory in the Chilean Atacama Desert, are searching for the stuff that jewelry is made of. Developed by Radboud University, the Netherlands Research School for Astronomy, and KU Leuven, BlackGEM scans the sky looking for some of the most dramatic explosions in the Universe. When black holes or neutron stars merge with each other they create ripples in space-time called gravitational waves. These waves can be detected with sensitive facilities like LIGO or Virgo, but what if we could study the actual merger event in even more detail? BlackGEM can home in on the location of a merger by probing large areas of the sky in visible light, looking for the faint afterglow that may result from these cosmic collisions. When BlackGEM has found one of these sources, the true treasure ...

22 avril 2024: This Picture of the Week, taken with ESO’s Very Large Telescope, captures the galaxy NGC 4383 evolving in a strange way. Gas is flowing from its core at a staggering rate, hurtling from the galaxy at average velocities over 200 km/s, and up to 300 km/s. This mysterious gas eruption has a unique cause: star formation. Large amounts of stars are being born at the centre of this galaxy. The most massive ones lose mass over their lifetimes through powerful winds, and end up dying in violent supernova explosions. These stellar winds and supernovae drag away some of the galaxy’s gas reservoir: the bright red filaments seen in this image show hydrogen gas ejected out to at least 20 000 light-years from the galaxy. Since this gas is carried away from the galactic core instead of remaining to form the next generation of stars, this process regulates the rate at ...

15 avril 2024: At first glance, this shot might look straight out of the “Dune” films, but this spectacular sunset scene actually takes place in the Atacama Desert in northern Chile, where the air is so dry and clean that colours shine through more vividly. This desert’s rocky and sandy landscape may not hide mind-bending “spice” or giant worms, but it holds something arguably as precious — can you see its silhouette in the distance? The Atacama Desert’s privileged atmospheric conditions make it an excellent location for ground-based observations of the cosmos. In the photo, ESO staff member Simon Lowery poses on Cerro Armazones, where construction for ESO’s Extremely Large Telescope is well underway. On the mountain range behind him stands ESO’s Paranal Observatory — you can see the domes of our Very Large Telescope (VLT) and the VLT Survey Telescope on the central peak and the Visible and Infrared Survey Telescope for ...

8 avril 2024: Located in the picturesque southern constellation of Centaurus, the Gum 41 nebula takes up most of this image brought to you by the VLT Survey Telescope, hosted at ESO’s Paranal Observatory in Chile. Let’s take a closer look at this intricate structure. Set against a colorful backdrop of stars, Gum 41 is a pleasantly symmetric example of a Strömgren sphere: a shell of hydrogen gas atoms glowing in rosy hues due to the radiation of the dazzling central star. While this star, called HD 100099, may appear to be one very bright object, it is actually thought to be two young, massive stars orbiting in such a tight embrace that they cannot be separated at the scale of this image. This romantic region is home to many pairs like this, including the luminous object on the lower right outskirts of the nebula, HD 99944. Sadly, the love story in these ...

1 avril 2024: Tucked away in ESO’s La Silla Observatory in Chile, this humble telescope is one of three in the groundbreaking French ExTrA project, discovering stars with Earth-like planets in the Milky Way and probing their environments. But how do these triplets tell us so much about systems many light-years away? When a planet orbiting its host star passes between it and the Earth, it blocks a small but detectable amount of light, similar to how the Moon blocks light from the Sun in a solar eclipse. ExTrA targets red dwarf stars, which are smaller than our Sun. This means that Earth-sized planets will block a larger proportion of their total light and are therefore easier to find. Even better, ExTrA observes these red dwarfs across a range of colours to learn more about a planet’s atmosphere, using a method called spectroscopy. The best contenders can be studied in greater detail with ...

25 mars 2024: This image looks straight out of a science fiction film on an alien planet, but it’s very real and happening here on Earth. The landscape is the Chajnantor plateau, about 5000 metres high in the Chilean Andes. The antennas are part of the Atacama Large Millimeter/submillimeter Array (ALMA), a telescope ESO operates together with international partners. But why is one of them mounted on a gigantic truck? ALMA comprises 66 high-precision antennas: a main array of 50 antennas, each 12 metres wide, and an additional compact array of four 12-metre and twelve 7-metre antennas. The ALMA antennas act together as a single telescope: antennas close to each other have higher sensitivity to detect extended sources, while those further away can see very fine details. The antennas of the main array can be arranged in different configurations on 192 pads across the entire site, where the maximum distance between them can ...

18 mars 2024: This Picture of the Week shows the stunning night sky over the Swedish–ESO Submillimetre Telescope (SEST) telescope at ESO’s La Silla Observatory in Chile. Until its retirement in 2003, SEST used its 15-metre main dish to observe the cold gas clouds where stars form. Now the telescope, perching at 2375 metres altitude, watches silently over the landscape of the Atacama Desert. While SEST stands in one of the darkest places on the planet, the sky itself isn’t completely black — rather the opposite! Here, besides thousands of stars, the picture features shades of red and green across the sky — an atmospheric phenomenon called airglow. In the bottom-left part of the sky we can see a portion of the band of the Milky Way, our home galaxy, and in the top half, two cloud-like structures that look like galactic fireworks. These are the Large and Small Magellanic Clouds, two dwarf ...