Picture of the Week

24 May 2021: In this image, the first rays of the morning Sun shine down upon Cerro Paranal in northern Chile, the home of ESO's Very Large Telescope (VLT) — signalling that another successful night of observations has concluded at the world’s most productive ground-based astronomical facility. Rising 2635 metres above sea level, the VLT’s site is amongst the best in the world for gazing deep into the Universe. Giving a sense of the site’s altitude is the apparent “sea” in the background. This is, however, a trick of the eye; the Atacama Desert, where ESO’s VLT is located, is a very dry place. Rather than liquid water, the distant, blue-hued sea is instead composed of clouds that form at lower elevations. Link: Panoramic image of the VLT

17 May 2021: ESO's La Silla Observatory stretches out before your eyes in this image taken by ESO Photo Ambassador Gerhard Hüdepohl. This perspective looks down from a mountaintop in the Chilean Atacama Desert, capturing numerous telescopes and support buildings winding through the barren, remote landscape. The telescope sitting proudly in the foreground is the ESO 3.6-metre telescope, with its curved white dome and grey base. A small bridge connects the telescope to a similarly white-domed, skinnier cylinder — the now-decommissioned ESO Coudé’ Auxiliary Telescope. In the distant background, a series of low, rectangular buildings can be seen sprawling across the mountainside; these include the site’s operations centre, dormitories, and a hotel. As this image attests, no other signs of human civilisation exist for many kilometres around. Sitting at a challenging altitude of 2400 metres and on the outskirts of the driest desert on the planet, La Silla has little chance of becoming ...

10 May 2021: This week’s picture of the week features DG121, an HII region — a cloud of ionised hydrogen — located in the constellation of Puppis (the Stern). HII regions, a type of emission nebulae, are created when young, massive stars release enough ultraviolet energy to ionise the surrounding gas clouds. These regions tend to have irregular structures and lack sharp boundaries, giving them their hazy, yet photogenic, appearance. The brightest star in the DG121 region, seen near the centre in this picture, is HD 60068. This spectacular image was taken with the FORS 2 (FOcal Reducer and low dispersion Spectrograph 2) instrument on ESO’s Very Large Telescope in the Chilean Atacama Desert. This instrument has been described by astronomers as "the Swiss army knife of instruments at Paranal", because of its ability to study many different astronomical objects in many different ways.

3 May 2021: This Picture of the Week appears to show a lone antenna gazing at the sky — but in reality this antenna is far from lonely. It is part of the Atacama Large Millimeter/submillimeter Array (ALMA), a telescope that comprises 66 high-precision antennas spread out across the Chajnantor plateau, located high up in the Chilean Andes. In this image we are treated to a spectacularly multi-coloured view of the sky above ALMA: green airglow hovers above the horizon, the Large Magellanic Cloud peeks out from behind the antenna, and the magnificent sprawl of the Milky Way stretches out overhead. These antennas are optimised to collect light at millimetre wavelengths, between infrared and radio waves, giving ALMA a view of the Universe that is very different to our own. Human eyes have evolved to see visible light while ALMA views the cosmos at longer wavelengths, picking up light from some of the ...

26 April 2021: Do you ever get the feeling that you're being watched? This friendly-looking object is the result of two galaxies merging into one another, complete with a pair of eyes hiding two growing supermassive black holes and a swirling grin. Such mergers are rare in our galactic neighbourhood; Mrk 739 is close enough (astronomically speaking) to study the event in detail, and thus gain a better understanding of the dramatic processes that take place during these cosmic mergers. By using the MUSE instrument on ESO’s Very Large Telescope, the team of astronomers, led by master’s student Dusán Tubín at the Pontificia Universidad Católica de Chile, were able to study the effects of both the merger and the radiation emitted by the growing gigantic black holes. Their study answers questions about the motion of the galaxies, the age of their stars, and the elements they are made up of. They have found ...

19 April 2021: This panoramic selfie was taken on 9 April 2016 by ESO Photo Ambassador Petr Horálek. Petr was in the Chilean Atacama Desert as a member of ESO’s Fulldome Expedition team, a select group of photographers who captured an array of stunning, ultra-high-definition visuals for use primarily in the ESO Supernova Planetarium & Visitor Centre. The landscape looms large around photographer Petr in this image, making him appear small beneath the striking Chilean sky. He can be seen standing just beneath a column of zodiacal light — perfect positioning that makes this image appear even more otherworldly. The wide, round-topped objects visible here are some of the 12-metre antennas comprising the Atacama Large Millimeter/submillimeter Array (ALMA). ALMA is the largest ground-based astronomical observatory in the world, and is located on the Chajnantor Plateau in Chile at an altitude of 5000 metres. A total of 66 antennas make up the array, and ...

12 April 2021: Great care is taken to ensure that the site for a new telescope will provide the best possible observing conditions. This picture of the week was captured in 2019 by ESO photo ambassador Petr Horálek from the top of Cerro Armazones, Chile, where the Extremely Large Telescope (ELT) is being constructed. Situated in the heart of the Atacama desert, at an altitude of 3046 metres, this high and dry location will be vital to showcase and utilise the ELT’s incredible observational power. This extraordinary panorama of the Atacama desert frames a sprawling view of our own Milky Way galaxy, seen with stunning clarity as a result of the minimum light pollution in this remote area. Massive interstellar dust clouds obscure the more distant starlight, leading to the distinctive “mottled” band in the night sky.

5 April 2021: The Atacama Desert in Chile is one of the darkest and most peaceful astronomical sites on Earth — and has, as a result, proven to be the perfect location for ESO’s various observatories and powerful instruments. This view shows ESO’s Paranal Observatory, home to the behemoth Very Large Telescope (VLT). The constituent telescopes of the VLT can be seen standing sentinel beneath a star-studded sky featuring the glittering arch of our Galaxy, and the glowing Magellanic Clouds (left). As this image demonstrates, the sky over Paranal isn’t completely dark; after sunset, the beauty of the Universe is overshadowed by that of Earth’s own atmosphere, which glows in multiple hues and paints the sky like a watercolour. The playful brushstrokes of the faraway emission nebulae that adorn the Milky Way and the constellation of Orion (The Hunter) in the upper centre of the frame, are joined by the soft swaths of ...

29 March 2021: This gently glowing area of sky is actually a hot bubble of hydrogen gas — named Sh 2-305 — that has been bombarded by intense radiation from nearby stars. Such gas clouds are known as emission nebulae, or HII regions (pronounced “H-two”). The radiation in question is in the ultraviolet part of the spectrum and is thought to emanate from at least two O-type stars, and likely several others. This stellar class is the brightest and hottest that we know of — such stars can be up to 90 times as massive as the Sun, and an incredible one million times as bright. Together with five neighbouring bubbles, Sh 2-305 belongs to a giant complex of dense clouds of dust and gas and, on a larger scale, an enormous ring called the GS234-02 star-forming supershell (located in the Perseus arm of the Milky Way, in the constellation of Puppis). This ...

22 March 2021: Humans have gazed up at the skies for a very long time, fascinated by the flowing shape of the Milky Way, the bright lights of the stars and planets, and the dark patches that obscure regions of sky. Different cultures had various names for these features; this Picture of the Week shows one object that has taken on several different identities over time, alongside an antenna of the Atacama Large Millimeter/submillimeter Array (ALMA). At the very top of the frame, within the band of the Milky Way, lies a pair of bright stars. These form part of Crux (The Southern Cross), one of the most recognisable constellations in the southern sky. Just below Crux, a dark, irregular shape is silhouetted against the central band of our galaxy. This is a prominent dark nebula lying just 600 light-years away: a giant cloud of molecules so dense it blocks out the light ...

15 March 2021: At first glance, this image may be more than a little confusing — is the domed telescope at the centre of the image part of a framed roadside photograph? Is it floating in mid-air? What, exactly, is going on? Sadly, nothing as exciting as a levitating telescope — this is simply a trick of peculiar perspective and clever camerawork. Here, the Danish 1.54-metre telescope is perfectly framed and reflected in one of the many roadside mirrors around ESO’s La Silla Observatory. The telescope appears to point towards the Large Magellanic Cloud (LMC) as if it were observing. The LMC is a small nearby galaxy that orbits the Milky Way and can be seen lurking in the upper left of the image. Due to the extremely sensitive technique used, a soft green radiance known as airglow, caused by the faint emission of light in Earth’s atmosphere, can be seen sweeping across ...

8 March 2021: Even after the Sun has set over ESO’s Paranal Observatory in Chile, the site is not truly dark. Although light pollution is practically non-existent at the remote site high up in the Atacama Desert, as daylight disappears the flowing dunes are instead illuminated by the dazzling light streaming from the stars above. The only artificial illumination for miles around comes from Paranal’s facilities, including the telescopes themselves and the Residencia, photographed here. A true oasis in the desert, the Residencia is a refuge from the harsh environment of the Atacama. The astronomers and other employees who work at ESO’s Paranal Observatory, located just a few kilometres down the road and home to ESO’s Very Large Telescope, can escape the arid environment after a long shift and enjoy a walk through the indoor garden or a dip in the swimming pool. The Residencia’s striking visual design is complemented by its world-leading ...

1 March 2021: On occasion, the Atacama Large Millimeter/submillimeter Array (ALMA) at the Chajnantor plateau in northern Chile experiences something you might not associate with an astronomical observatory — snow! When snow falls and coats the landscape with a frosty glaze of cool white, the entire site is transformed. It becomes something almost subterranean or extra-terrestrial, reminiscent of a rebel base from Star Wars or a dystopian scene from Blade Runner. A number of ALMA’s 66 high-precision radio antennas can be seen in this image, connected by cleared pathways. The array spends its time observing the cool Universe and its phenomena — star formation, molecular clouds, and the early Universe.

22 February 2021: Appearing as a bird in flight, with wings outstretched in the expanse of space, SU Aur, a star much younger and more massive than the Sun, is surrounded by a giant planet-forming disc. This image, captured by the SPHERE instrument on ESO’s Very Large Telescope (VLT), shows the disc around SU Aur in unprecedented detail, including the long dust trails connected to it. The star itself is obscured by the instrument’s coronagraph, a device that blocks the light from the central star to allow the less bright features around it to stand out. The dust trails are composed of material from an encompassing nebula flowing into the disc. This nebula is likely the outcome of a collision between the star and a huge cloud of gas and dust, resulting in the unique shape of this planet-forming disc and the surrounding dust structure. A new study of SU Aur, which used ...

15 February 2021: It may not be as famous as Halley’s Comet, but Comet 252P/LINEAR can still put on a show! In late March 2016, the comet made one of the closest approaches to Earth of all comets in history — just over 5.3 million kilometres distant, compared to Halley’s closest approach of 87 million kilometres. The light of Comet 252P/LINEAR is not elongated in a classic tail, but instead appears as a soft round glow, tinged green due to molecules of diatomic carbon fluorescing in the sunlight. This image from April 2016 captures the distinctly green comet: you can spot it just above the Milky Way, between the galaxy’s starry arch and the Very Large Telescope (VLT) Unit Telescope at the centre of the frame. ESO’s VLT is located at the Paranal Observatory in Chile, an ideal location for comet-spotting. Paranal is one of the most spectacular observatories in the world, situated ...

8 February 2021: Discovered in the year 1836 by John Herschel, NGC 6902 is a beautiful spiral galaxy located more than 130 million light-years away in the constellation of Sagittarius, the Archer. This image was taken with MUSE, the Multi Unit Spectroscopic Explorer instrument attached to one of the four 8.2-metre telescopes that make up the VLT, and shows the galaxy from a unique perspective. A zoom in towards the galaxy’s centre, the image shows a nuclear ring where the orange glow of intense star formation is visible. Inside this ring lies a faint and small bar of stars. Researchers found that stars within it are distributed differently depending on their age, with younger stars aligned along the bar and older stars more dispersed. These locations of the young and old stars within the central bar of NGC 6902 confirm predictions made years earlier from simulations and models. This is the first time ...

1 February 2021: This beautiful photograph of the southern sky was taken by ESO Photo Ambassador Petr Horálek from ESO’s Paranal Observatory in Chile. Petr was not alone at Paranal. Standing to the bottom left of the image, next to an Auxiliary Telescope of the Very Large Telescope Interferometer (VLTI), are astrophotographers Yuri Beletsky and Babak Tafreshi, both of whom are also Photo Ambassadors for ESO. The duo are seen beneath a sky filled with stunning phenomena. The bright, dominant band of the Milky Way cuts across the sky, with the Gum Nebula (Gum 12) appearing at the top of the frame in red. The Large Magellanic Cloud, a satellite galaxy of the Milky Way, is an especially bright blotch to the centre right — just below Canopus, the brightest star in both this view and the southern constellation of Carina. A beautiful green and reddish shimmer is also visible at the bottom ...

25 January 2021: The road to ESO’s La Silla Observatory in the Chilean Atacama Desert appears to curve around the mountain and collide with the downward slope of the Milky Way in this Picture of the Week. Small yellow bulbs light up the road at regular intervals; it is prohibited to use headlights on these roads between dusk and dawn, as even dim lights can interfere significantly with telescope observations. The site enjoys some of the darkest night skies on Earth. The darkness, high altitude, and resulting dry air at La Silla make it an exceptional location for astronomy. In the foreground of this image, the Danish 1.54-metre telescope is performing its nightly observations. Its instruments have allowed astronomers to achieve several “firsts”. In 2005, for example, astronomers observed the afterglows of short gamma-ray bursts and showed that the bursts are likely caused by the dramatic collision of two neutron stars, while in ...

18 January 2021: Far from civilisation, deep in the barren, mountainous terrain of Chile’s Atacama Desert, stand four pillars of modern astronomy: the enormous and angular enclosures of the Unit Telescopes (UTs) of ESO’s Very Large Telescope. The Sun’s diffuse orange glow peeking over the horizon is no match for the light display filling the sky above. Containing hundreds of billions of stars, the great bow of the Milky Way stretches across the panorama, dipping down to touch the horizon. The mottled look of our home galaxy is due to huge clouds of interstellar dust obscuring more distant starlight. Bright stars, celestial objects, and other phenomena in our cosmic neighbourhood hang like lanterns in the Chilean sky, backlit by ethereal red and green airglow. Alone, each UT can make magnificent observations of the Universe from their home at ESO’s Paranal Observatory — but the four telescopes can also work together and observe the ...

11 January 2021: Captured with the MUSE instrument on ESO’s Very Large Telescope (VLT), this image of the distant spiral galaxy NGC 1097 shows a textbook example of a star-bursting nuclear ring. Located 45 million light-years away from Earth, in the constellation of Fornax, this ring lies at the very centre of its galaxy. It spans only 5,000 light years across, being dwarfed by the full size of its host galaxy, which extends some tens of thousands of light-years beyond its centre. The darker lanes seen in this MUSE image show dust, gas and debris from the galaxy (or possibly from a satellite galaxy), which are being funnelled into the supermassive black hole at its centre. This process heats up the surrounding matter forming an accretion disc around the black hole and launching huge amounts of energy into the surrounding area. Nearby dust is heated up and star formation accelerates in the area ...