Picture of the Week

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 ...

16 November 2020: To the right of this image captured in northern Chile, the eye-catching arc of the Milky Way soars above the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner. But despite the breathtaking view, the glow of our home galaxy is here rivalled by another type of interesting light. The image also shows, on the arc to the left, a faint brightening of the night sky in the region of the ecliptic directly opposite the Sun. This phenomenon is known as gegenschein (German for “countershine”) and is created as interplanetary dust in the outer part of the Solar System — from comets and broken-up asteroids — scatters incoming sunlight. In most parts of the world, phenomena such as gegenschein, or the stunning arc of the Milky Way, are masked by light pollution from artificial light sources. Some estimates indicate that over 80% of the world’s population lives under ...

9 November 2020: At first glance, this image looks both awesome and intimidating, with the enormous beams of light resembling some terrible cosmic weapon. Fortunately, that is not the case! This ESO Picture of the Week shows something far more benign — a mixture of gas, dust, and powerful lasers. Among the largest nebulae in the southern night sky, the Carina Nebula is a perfect viewing target for ESO’s Very Large Telescope (VLT). In this image, the nebula appears as a stunning pink cloud in the clear sky above ESO’s Paranal Observatory in Chile, home of the VLT. The Carina Nebula is a vast cloud of dust and gas — this gas is ionised and made to glow by the stars within the nebula itself. The cutting-edge Adaptive Optics Facility installed on one of the 8.2-metre Unit Telescopes (UTs) of the VLT is in full operation here. The orange laser beams are sent ...

2 November 2020: The otherworldliness of this image, obtained at ESO’s Very Large Telescope (VLT) in northern Chile, is due to a combination of natural and artificial light phenomena. This ethereal image captures a lunar halo on rare cloudy skies over ESO’s Paranal Observatory. This optical phenomenon is created when moonlight is refracted by millions of small ice crystals and water droplets in the surrounding atmosphere. These haloes are reasonably common; however, they require quite a bit of light to appear, so the Moon must be in a specific position relative to the Earth and the Sun to reflect enough light to produce a fine ring like this one. This particular halo comprises multiple coloured bands that are formed in the same way as in a rainbow — light of different wavelengths is refracted by varying amounts. White light is thus broken into its constituent parts, dispersing to create a spectrum of ...

26 October 2020: ESO’s New Technology Telescope (NTT) has captured the familiar sight of three of our planetary neighbours as limited science operations restart at La Silla Observatory, located in the Chilean Atacama desert. Images of the three brightest planets visible in the sky that night: Jupiter, Mars and Saturn were taken as the operations team tested the NTT’s versatile EFOSC2 instrument. The subtle orange, yellow and reddish hues of the three planets are seen by combining images captured by the instrument using five different filters. This Picture of the Week shows a montage of the images taken of the three planets. The relative sizes seen in this montage are proportional to the angular size of the planets in the sky. Mars appears rather large and bright because it was in opposition when the image was taken, that is, the Earth was positioned between Mars and the Sun. Following these successful tests, very ...

19 October 2020: Winter nights on the Chajnantor Plateau can seem incredibly isolating — but the wonder of some of the driest, darkest skies in the world is definitely something to be shared. This image shows two of the 66 antennas that comprise the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, as they work together to observe the skies in millimetre and submillimetre wavelengths. These wavelengths are notoriously difficult to observe, as water vapour in the atmosphere absorbs this kind of light and prevents it from reaching the ground. To catch sight of it, telescopes must be placed at very high altitudes where the air is drier and less absorbent. For ALMA, that means an elevation of 5000 metres. Hanging above the pair of telescopes is the constellation of Orion (The Hunter), identifiable by his distinctive star-studded belt. His shoulder is marked by the red supergiant Betelgeuse, on the ...

12 October 2020: In this eye-catching Picture of the Week, bright star trails fill the sky above ESO’s La Silla Observatory in Chile. Such trails are formed by the Earth spinning on its axis — our planet’s rotation causes the stars to seemingly move through the sky, slowly tracing out perfect concentric arcs and circles as they do so. A photograph like this therefore requires a long exposure to capture the passage of time. At the centre of this image is the decommissioned Swedish-ESO Submillimetre Telescope , and the ESO 3.6-metre telescope sits atop the mountain to the left, aglow with activity. This telescope hosts HARPS (the High Accuracy Radial velocity Planet Searcher), which searches for exoplanets by measuring the tiny “wobbling” motions of their host stars as the planets sweep around in their orbits.

5 October 2020: Images such as this one really highlight the movement of our planet through space. As well as travelling on an elliptical path around the Sun, the Earth spins on its axis — and it is this rotational motion that’s responsible for this eye-catching view. As the Earth rotates, the stars above appear to change position and move through the sky on long arches, creating these eye-catching star trails centred on the south celestial pole. To successfully capture the apparent motion of the stars, photographer Fred Kamphues took multiple long-exposure shots and stacked them together, creating this remarkable photograph. The illuminated road below leads up to Paranal Observatory, home to ESO’s Very Large Telescope (VLT). In this image, two of the four main Unit Telescopes (UTs) and the VST can be seen atop the mountain (Cerro Paranal). It is the laser beams from one of these UTs, emphasised by ...