Picture of the Week 2024

25 March 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 March 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 March 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 March 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 February 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 February 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 ...

12 February 2024: Hundreds of thousands of stars are contained in this Picture of the Week, an infrared image of Sagittarius C, a region near the centre of the Milky Way. Taken with ESO’s Very Large Telescope (VLT) in the Chilean Atacama Desert, this image is helping astronomers unlock a stellar puzzle. The centre of the Milky Way is the most prolific star-forming region in the entire galaxy. However, astronomers have only found a fraction of the young stars they expected here: there is “fossil” evidence that many more stars were born in the recent past than the ones we actually see. This is because looking towards the centre of the galaxy is not an easy task: clouds of dust and gas block the light from the stars and obscure the view. Infrared instruments, such as the HAWK-I camera on the VLT, allow astronomers to peer through these clouds and reveal the starry ...

5 February 2024: Why use just one telescope to observe the sky? The plateau of Cerro Paranal, seen under the moonlight in this Picture of the Week, hosts ESO’s Very Large Telescope Interferometer (VLTI), an indomitable team of four 8.2-metre Unit Telescopes (UTs) and four additional 1.8-metre Auxiliary Telescopes (ATs). An interferometer precisely combines light from separate telescopes observing the same object in the sky, allowing astronomers to see the cosmos in incredible detail. The VLTI uses either a combination of the ATs or the UTs. The ATs, one of which is seen front and centre, are set on tracks so they can be moved to 30 predefined positions on the platform, in different configurations; each arrangement allows astronomers to observe different levels of detail. While the ATs are specifically designed for the VLTI, each UT can be also used as an independent telescope. One of the UTs is equipped with lasers that ...

29 January 2024: Like a flower following the Sun, the dome of ESO’s Extremely Large Telescope (ELT) will be able to rotate to allow the telescope to track objects in the sky. Seen under the bright blue skies of Cerro Armazones in the Chilean Atacama Desert, this video shows a test of the dome rotating for the first time. The test moved the dome 10 m in either direction at 1 cm/s, but the final operating speed will be a walking pace of 5 km/h. The test was performed by engineers of Cimolai, the company contracted by ESO to design and build the ELT dome and telescope structure. The humans hard at work in this sped-up video show, for scale, the sheer size of the telescope dome. Rotating the dome is no small feat, as its skeleton currently weighs about 2500 tons, and will eventually weigh around 6100 tons when finished. This first ...

22 January 2024: In December 2023, the first 18 segments of ESO’s Extremely Large Telescope (ELT) main mirror embarked on a whirlwind 10 000 km journey from Europe to the Chilean Atacama Desert. This Picture of the Week captures the moment of truth when ESO engineers at the ELT Technical Facility unveiled one of the segments to ensure it had arrived safely at ESO’s Paranal Observatory. Due to the sheer size and fragility of the mirror segments —each mirror is five centimetres thick, 1.5 metres wide and shaped to nanometre accuracy— they were each shipped in a private, protective cocoon. Each box was equipped with humidity, temperature and shock sensors to track the internal conditions during the long journey. When loaded into the transport vehicles, the boxes were cushioned by air bags. Upon arrival at the technical facility, the segments were carefully inspected to ensure they hadn’t been damaged during delivery. With the ...

15 January 2024: The Vela constellation is visible with the naked eye in the southern sky, but you might miss a lot of details hidden there, like those shown in this Picture of the Week. This is a small patch of the Vela supernova remnant, the intricate leftovers of the explosion of a massive star 11 000 years ago. This image is part of a huge and detailed mosaic captured with the VLT Survey Telescope (VST), hosted at ESO’s Paranal Observatory in the Chilean desert. Pink and orange filamentary clouds swarm around in this picture, resembling the ghostly shadow of a cosmic bird with wide orange wings, a long pink body, and a bright pinkish star as an eye. A myriad of stars are sprinkled all over the image. When massive stars reach the end of their life they explode as supernovae, expelling their outer layers. These explosions send out shock waves that ...

8 January 2024: The high altitude and dry air of the Chajnantor plateau give the Atacama Large Millimeter/submillimeter Array (ALMA), operated by ESO and its international partners, an optimal window to study the cold dark universe. In this striking Picture of the Week, the rolling, rusty and barren landscape of the plateau feels more like an alien world, rather than our own planet. Thankfully, a familiar friend brings us back to Earth — the full Moon rising at sunset. Over the different lunar phases, the moon rises and sets at different times, while over the course of the year, it rises and sets in different locations on the horizon. Set against the horizon during its rise, the moon often seems to loom larger than usual. But this is only a trick on your eyes due to a famed optical illusion. Our Moon is a unique body within the solar system; it’s Earth’s only ...

1 January 2024: Firework displays are used to mark the beginning of the New Year all over the world, so we thought we’d bring you our own, space-themed display to kick things off in 2024. This Picture of the Week is a time-lapse video of the night sky above ESO’s Very Large Telescope (VLT) on Cerro Paranal, Chile. Look closely, and you’ll catch a glimpse of an extraterrestrial firework, otherwise known as a meteor. Meteors are objects from outer space that burn up as they enter Earth's atmosphere at high speeds. Often called “shooting stars” or “fireballs”, they create dazzling displays as they crash through our gaseous atmosphere, heating up as a result of friction with the air. In this sped-up time-lapse, captured in June last year, the meteor left behind a trail of smoke that slowly dispersed in the atmosphere. By some estimates, 44 tonnes of meteoric material fall into Earth’s atmosphere ...