Photo de la semaine 2025

3 mars 2025: Apart from actually going to space, you probably won’t feel much closer to the stars than at the top of the staircase at ESO’s Paranal Observatory shown in this picture. At 2635 metres (plus some twenty steps) above sea level in the Atacama Desert of Chile, you see a wealth of stars that remain hidden in other places, because Paranal boasts the darkest skies of all major observatories on Earth. At first glance, the centre of the Milky Way has turned itself into a dragon with a strange, orange tongue. But the only thing sneaking up on you in this Picture of the Week is the sheer beauty of the night sky. This is just a normal night for ESO’s Very Large Telescope (VLT), which has its home in Paranal. The bright yellow beams are the VLT’s laser guide stars, shooting up from the telescope (to the right, but outside ...

24 février 2025: Last year saw outstanding progress for ESO’s Extremely Large Telescope (ELT). In this Picture of the Week, we’re looking back in time to see just how far the ELT has come. At first, we can see only a skeletal steel dome, which over the course of the year has been gradually coated in a shiny new layer of protective — and thermally insulating — cladding. Panel by panel, the enormous 80 m high, 93 m wide structure is being wrapped in a warm blanket of aluminium and other thermal regulators. This will help to keep the air inside the telescope at the expected temperature of the next night, and defend it from the sand and dust of the ELT’s harsh desert environment. But that's not all, as this timelapse also shows how much progress has been made building the ELT’s main structure. Growing like a great white crystal at the ...

17 février 2025: This Picture of the Week shows NGC 3640, an unusual elliptical galaxy 88 million light-years away. The image, taken with the VLT Survey Telescope hosted at ESO’s Paranal Observatory, reveals a menagerie of galaxies of all shapes and sizes, ranging from slight blue smudges to the fried-egg shape of NGC 3640. But amidst this colourful cosmic neighbourhood, one thing stands out — this egg has a double yolk: a smaller galaxy that might be too close for its comfort. Throughout their extremely long lifetime, galaxies change. As they soar through space, they may steal gas and stars from other galaxies, or even engulf and merge with them. After these events, galaxies can become distorted, as exemplified by the misshaped NGC 3640 and the diffuse light around it. The galaxy is then left with ‘scars’ that hint at a violent past, which astronomers can use to know its past and present ...

10 février 2025: Bathed in the sunset light of Chile’s Atacama Desert, this Picture of the Week shows steady progress in the construction of ESO’s Extremely Large Telescope (ELT). From up here, the ELT’s white tube-like altitude structure is clearly the eyecatcher. The close-knitted truss structure at the bottom is the support cell of the ELT’s 39-m primary mirror, the largest telescope mirror ever made. The light it collects from the cosmos will bounce off to the secondary mirror, which will be held in the central ring seen at the very top of the picture. Light will then travel down again through the ELT’s central tower and its three additional mirrors, before it reaches the scientific instruments that will be located at the side of the telescope. At first glance, with no humans or bananas for scale, the steel structure might look modest in size. But the altitude structure alone is already more ...

3 février 2025: “Comets are like cats: they have tails, and they do precisely what they want,” wrote David H. Levy, an amateur astronomer who discovered 23 comets. These cosmic visitors can indeed be pretty capricious. We never know exactly how long a comet will be visible in the sky. In January, the southern hemisphere had a captivating visitor in the form of the comet C/2024 G3 (ATLAS). It looks magnificent in this Picture of the Week by Juan Beltrán, one of our engineers, who took it on 20 January at our Paranal Observatory in Chile. Just last year, another comet was also caught on camera visiting ESO Headquarters in Garching bei München, Germany. These so-called non-periodic comets only stick around in our skies for a few weeks. If you miss your photo opportunity, your next chance may be a few thousand years later… As comets approach the Sun they warm up, and ...

29 janvier 2025: Is there an invisible web of dark matter surrounding us? Its influence can be observed across the cosmos, but the web remains unseen… for the most part. This Picture of the Week shows the clearest image yet of a filament from this cosmic web. The filament was imaged with ESO’s Very Large Telescope, and is shown here in purple overlaid on a background image from the NASA/ESA Hubble Space Telescope. Made of gas clumped together by the influence of dark matter, the filament stretches out for 3 million light-years, connecting two distant galaxies in the early Universe. Around 85% of all matter in the Universe is actually dark matter. Dark matter is invisible, but the gas around it is not. This gas glows extremely faintly though, making these structures very difficult to observe. But after about 150 hours of observations, a team of astronomers led by Davide Tornotti, a PhD ...

20 janvier 2025: In this Picture of the Week, taken at the ESO Headquarters in Germany, you see the first of nine new lasers that are currently being built for two of ESO’s Paranal Observatory facilities, in Chile’s Atacama Desert. But why do telescopes need lasers? Not for shooting aliens, that’s for sure. Lasers are part of the telescopes’ adaptive optics system. As ESO’s observatories are ground-based, the turbulence in the atmosphere can blur our view of the cosmos, and with adaptive optics we can cancel this blurring out, in real time. The laser creates an artificial star by exciting sodium atoms in the atmosphere, around 90 kilometers high. A computer measures how the atmosphere distorts the light of this star and steers a shape-shifting mirror in the telescope to compensate for it. The result: sharper images. The light itself is generated in the laser source — the large grey box at the ...

13 janvier 2025: Astronomers have long thought that the upper clouds of Jupiter, which create the planet’s iconic pale brown belts, are made of frozen ammonia. But a new study, that brought together amateur and professional astronomers, has shown that these clouds are actually located lower in the atmosphere than we thought and are made of something completely different: most likely ammonium hydrosulphide mixed with smog. Citizen scientist Steve Hill previously showed that he could map the planet’s atmosphere by using only specially coloured filters and his backyard telescope. These results provided initial clues that the clouds were too deep within Jupiter’s warm atmosphere to be consistent with clouds made of ammonia ice. To check, Hill joined forces with Patrick Irwin at Oxford University, whose team had previously used the sophisticated MUSE instrument on ESO’s Very Large Telescope (VLT) to study the atmosphere of gas giants. MUSE is capable of scanning the atmosphere ...

6 janvier 2025: Astronomers mostly focus their attention on the sky, but sometimes it’s worth looking around our planet, too. At night, the star-spangled sky over Chile’s Atacama Desert steals the limelight, but once the barren landscape basks in sunlight again, other marvels are revealed. This Picture of the Week, for instance, could easily feature in a travel magazine. It is taken from Pukará de Quitor (Fort of Quitor), a stone fortress built centuries ago by the Licán Antai community, also known as Atacameños. You find it near San Pedro de Atacama, not far from where the Atacama Large Millimeter/submillimeter Array (ALMA) is housed, the radio telescope array which ESO operates together with its international partners. In this picture, the arch of the fortress is framing the Licancabur volcano, which looms up next to Chile’s border with Bolivia. On the mountain, other archaeological sites have been found, and its summit crater hides one ...