Picture of the Week

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 ...

4 January 2021: ESO’s Very Large Telescope (VLT) is one of the most advanced optical and infrared observatories in the world. This magnificent astronomical detective comprises an array of four individual Unit Telescopes — the large cylindrical domes visible in this image — each hosting a main mirror measuring 8.2 metres in diameter. It also includes four movable 1.8-metre diameter Auxiliary Telescopes — the, comparatively, small white, round domes seen to the left of the Unit Telescopes. The VLT has contributed to groundbreaking observations and discoveries, including snapping the first image of an extrasolar planet and observing the visible counterpart to a gravitational wave source. In this picture, the telescopes are resting, their domed eyelids firmly closed as they slumber at ESO’s Paranal Observatory in Chile — but at night they will awaken to observe the Universe and make more fantastic discoveries.

28 December 2020: The wonders of the cosmos have inspired awe since the dawn of time. Thousands of years ago, ancient civilisations observed celestial objects to mark the seasons and time, to weave myths and stories, and to make sense of the cosmos around them — and modern-day stargazers are captivated by the beauty and mystery of the night sky in the very same way. We have been turning camera lenses to the skies since the emergence of early forms of photography, hoping to capture the spectacle of a dark sky dotted with myriad pinpricks of light. But it wasn’t until 1850 that the first star was captured on camera. The following decades saw the development of increasingly complex camera equipment, and images of celestial objects and phenomena created using light from across the electromagnetic spectrum have since become the cornerstone of modern astronomy. This beautiful photograph of the glimmering arch of the ...

21 December 2020: As the unconventional year of 2020 draws to a close, we send you and all of your families our very best wishes! Undoubtedly this year has been challenging for many, and here at ESO we have worked to adapt to these unprecedented times. After a pause of a few months, we have restarted limited science operations at our observatories in Chile, under strict safety measures. As our telescopes and instruments resume their observations of the night sky, we continue to be inspired by the Universe’s wonders and look forward to sharing more fascinating astronomical discoveries with you all. On behalf of everyone at the European Southern Observatory, we hope you have a very safe and healthy end of the year and a brilliant start to 2021!

14 December 2020: The antennas comprising the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, appear to emit an eerie, vivid shade of green light in this Picture of the Week. Situated high up on the isolated Chajnantor plateau in Chile’s Atacama Desert, ALMA seems like the perfect place for friendly extraterrestrials to discreetly land and make contact…but something far more mundane is responsible for this otherworldly green glow. The light emanates from indicator lights, which show whether or not it is safe for staff to approach the antennas. A green light as pictured indicates that it’s safe to approach. An alien world is, however, visible above the antennas. In the top left of the image, in the clear Chilean sky, two bright stars can be seen next to each other within the band of the Milky Way. These stars are often called The Pointers, as they “point” towards the ...

7 December 2020: This photograph, taken by ESO Photo Ambassador Petr Horálek, looks west from ESO’s Paranal Observatory in Chile. The bright object at the centre of the frame is the Moon — slightly to its upper left is the ringed planet Saturn, while rocky Mercury sits to the lower left. Saturn and Mercury in conjunction can be difficult to see with the naked eye from some latitudes, but this breathtaking image captures them beautifully, despite the relatively bright light from the nearby Moon. The dusty Milky Way appears to split the sky horizontally, with a star-studded night view above and the last signs of the Sun lingering below. Many famous nebulae are visible across this cosmic curtain, such as the Lagoon Nebula, Cat’s Paw Nebula, and Trifid Nebula. The individual telescopes in this image together make up ESO’s Very Large Telescope (VLT), the world’s most advanced optical and infrared observatory. The VLT ...

30 November 2020: Resembling a river of light flowing through the dry, otherworldly landscape of northern Chile, the road to ESO’s Paranal Observatory is a lifeline for the facility. Sited in one of the most remote locations in the world to benefit from the extremely low light pollution there, the observatory can only be accessed by this road, which winds its solitary way through the calm, barren terrain. Atop the distant mountain, called Cerro Paranal, it is possible to see the tiny shapes of the VLT Survey Telescope, and all four of the Unit Telescopes (UTs) that make up ESO’s Very Large Telescope. Though small in this Picture of the Week, up close these telescopes are veritable behemoths — each UT mirror alone spans over eight metres! This photo was taken from the vantage point of another of ESO’s facilities, the VISTA telescope, on an adjacent peak in the Atacama Desert, ...

23 November 2020: The thousands of newly formed stars at the heart of NGC 5236 were imaged with the MUSE instrument, attached to ESO’s Very Large Telescope at Paranal Observatory in Chile. Referred to mostly as the Southern Pinwheel galaxy, NGC 5236 receives its common name from its beautiful spiral arm configuration and its location in a Southern Hemisphere constellation: Hydra. Bright regions of star formation light up this galaxy, including the region imaged here, located within the galaxy's centre. With the right conditions, and commonly within the spiral arms of a galaxy, cold molecular clouds mostly composed of hydrogen gas can collapse and form into brand new stars. In larger clouds, the burning of a new star can create a domino effect, initiating the collapse of the surrounding gas into even more stars. Within a galaxy’s centre however, other processes are at play. The supermassive black hole at the centre of NGC ...