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1. juli 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. juni 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. juni 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. juni 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. juni 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. maj 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. maj 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. maj 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. maj 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. april 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. april 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. april 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. april 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. april 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. marts 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. marts 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 ...

11. marts 2024: Astronomers are well-known for naming objects with odd conventions, and the cometary globule GN 16.43.7.01 seen in this Picture of the Week is no exception. Cometary globules have nothing to do with comets aside from appearance: they are named for their dusty head and elongated, dark tail, as seen in this image taken with the VLT Survey Telescope (VST) hosted at ESO’s Paranal Observatory in Chile. This globule, dubbed the Dark Tower — astronomers compensate with obvious names — lies about 5000 light-years away from Earth in the southern constellation Scorpius (the Scorpion). It contains dense clumps of collapsing gas and dust out of which stars will be born. The curious shape of this object is carved out from an intense bombardment of radiation from a cluster of young, bright stars located off-camera to the upper-left. This radiation has swept around and outlined the cometary globule with the characteristic pink ...

4. marts 2024: A watched pot never boils, but luckily that doesn’t apply to us watching ESO’s Extremely Large Telescope (ELT) being constructed. This Picture of the Week shows a timelapse overlooking Cerro Armazones in the Chilean Atacama Desert over the course of 2023, as the dome of the ELT is pieced together in smooth choreography. Partly built at a nearby base camp, large steel elements arrive at the peak ready to be neatly assembled together into the dome. The steel structure provides the skeleton around which a protective insulated cladding is now being applied. It rests on a concrete foundation separated from the central pier where the telescope will be, to reduce vibrations propagating through the ground. The dome can rotate on 36 trolleys, allowing the telescope to observe the whole sky. A new webcam inside the dome shows progress in the azimuth structure that will support the telescope, as well as ...

26. februar 2024: Appearing to cut through the Moon in this Picture of the Week is one of the laser guide stars on Unit Telescope 4 (UT4 or Yepun), one of the four 8.2-m telescopes of ESO’s Very Large Telescope (VLT). At any altitude, ground-based telescopes are affected by the atmospheric distortion of astronomical light. To counteract this, astronomers use adaptive optics in which a flexible mirror is deformed in real time to counteract this effect, yielding sharp images. The laser you see here, a powerful beam of light, excites sodium atoms 90 kilometres high in the atmosphere, consequently producing a glowing artificial star. Astronomers use this star to measure the blurring effect of the atmosphere and drive the deformable mirrors. To avoid disturbing airplanes, these lasers rely on an automated aircraft avoidance system. This system continuously monitors the sky and instantly switches the lasers off whenever an aircraft’s trajectory is predicted to ...

19. februar 2024: A small step is being taken up the stairs to one of the BlackGEM telescopes in this Picture of the Week, but this facility represents a giant leap in gravitational wave studies at ESO’s La Silla Observatory in Chile. BlackGEM — which was developed by Radboud University, the Netherlands Research School for Astronomy, and the KU Leuven and officially inaugurated in January 2024 — is a mostly robotic array of optical telescopes designed to scan the southern sky. Each telescope in the array is aimed at different parts of the clear sky above La Silla, ever ready to detect the visible light afterglow of gravitational wave sources — cataclysmic events such as merging neutron stars or black holes. BlackGEM will pinpoint where these sources are and provide astronomers with a target for follow-up observations with other, larger telescopes to learn more about them. From the southern hemisphere, astronomers also have ...