Picture of the Week

11 November 2019: The telescopes at ESO’s La Silla Observatory in Chile are on a mission to observe and understand the vast Universe — but there are plenty of interesting natural phenomena far closer to home. One such example is this angelic 22-degree halo. This photo was taken high up in the remote Atacama Desert, but such a sight is visible year-round all over the world. These haloes are formed when light from the Sun or Moon passes through cirrus clouds high up in the Earth’s atmosphere. The tiny ice crystals that make up these clouds act as miniature prisms, changing the direction of the light that passes through them (something known as refraction). Light rays that do this tend to “bunch up” at the angle that represents the least amount of deviation from their original path. For the particular shape of ice crystal lurking within the cirrus clouds, this minimum deviation angle ...

4 November 2019: This seldom-seen perspective offers a true insider’s view of one of ESO’s world-leading telescopes: the VLT Survey Telescope, or VST. The VST is installed at ESO’s Paranal Observatory in Chile. It is the largest telescope surveying the sky in light visible to humans and its cutting-edge design makes it a powerful tool for studying the Universe. From this viewpoint the OmegaCAM instrument — a camera with a large field of view — can be seen front and centre, nestled inside its stabilising control structure. When night falls the telescope’s dome opens and the VST gets to work. The high altitude and arid conditions of the Atacama Desert provide the perfect conditions for astronomical observing, delivering cloud-free skies and very low light pollution for the vast majority of the year. This allows for truly spectacular views of the Milky Way overhead, complete with its array of striking colours, streaks of dark ...

28 October 2019: This strikingly simple and serene view of NGC 1404 — a giant elliptical galaxy located 62 million light-years away in the constellation of Fornax (The Furnace) — hides the galaxy’s cruel reality. NGC 1404 is one of the galaxies comprising the massive Fornax Cluster — and it is slowly falling inwards towards the cluster’s core. As it moves towards the cluster’s large centremost galaxy, NGC 1399, the galaxy’s reserves of hot gas are being forcibly ripped and stripped away, leaving an elongated tell-tale trail of gas in its wake. While not visible in this image, this gas stream can be seen clearly in X-ray images of the galaxy; in time, NGC 1404 will lose most of its hot gas, and therefore its ability to form new stars. ESO’s Very Large Telescope (VLT) captured this image of NGC 1404 with its FORS instrument. The bright foreground star to the lower left ...

21 October 2019: In a remote part of Chile’s Atacama Desert, at an altitude of over 2600 metres, sits Paranal Observatory. In terms of total light-collecting area, it is the largest observatory in the southern hemisphere, and is home to several of ESO’s cutting-edge telescopes. The main peak, visible here directly beneath the eerily tranquil yellow Moon, hosts ESO’s Very Large Telescope (VLT) and the 2.6-metre VLT Survey Telescope (VST). The VLT’s four Unit Telescopes can be seen on top of this peak, next to the smaller Auxiliary Telescopes on the far left and the VST towards the right. As ESO continues to expand its array of telescopes in the southern hemisphere, more space is required for construction! A secondary peak around 1500 metres away from the VLT and VST — on the far right on this image — was chosen as the site for ESO’s Visible and Infrared Survey Telescope for ...

14 October 2019: Like many of ESO’s telescopes, the Danish 1.54-metre telescope at La Silla Observatory in Chile is accompanied by an all-sky camera that transmits views of the site 24/7, allowing anyone and everyone worldwide to see the telescope in action. Viewers can see astronomers and engineers at work, admire breathtaking night-time views of the Milky Way, and — if they’re lucky — spot some of the locals. This rare snap captures a native bird using the all-sky camera as a perch, perfectly unaware that it is blocking the view. The bird’s species remains an unsolved mystery; the image was taken at night so it is likely that the bird was out hunting, which suggests it is a nocturnal species. Despite the high and dry conditions of ESO’s observatories in Chile’s Atacama Desert, the area is home to a wide range of wildlife, such as llama-like Vicuñas, sharp-eyed Andean foxes, majestic birds ...

7 October 2019: This image features a comet located in the outer reaches of the Solar System: comet C/2016 R2 (PANSTARRS). As its name suggests, the comet was discovered in 2016 by the Pan-STARRS telescopes in Hawai’i. The new image seen here was captured by a project based at ESO’s Paranal Observatory in Chile named the Search for habitable Planets EClipsing ULtra-cOOl Stars — or SPECULOOS for short. Comets are balls of dust, ice, gas and rock. When they pass close to the Sun, their ice warms up, turns to gas, and escapes in a process called “outgassing”. This process forms fuzzy envelopes around the comets’ nucleus, called comas, and distinctive tails. Observations from SPECULOOS show that the tail of C/2016 R2 (PANSTARRS) changes dramatically across a single night, making for a dynamic set of images. The image shown here, and accompanying frames in the time-lapse movie, comprise observations taken on 18 January ...

30 September 2019: Using the detailed eyes of the Atacama Large Millimeter/submillimeter Array (ALMA) and ESO’s Very Large Telescope (VLT), astronomers have mapped the intense tails of a cosmic jellyfish: a number of knotty streams of gas spewing outwards from a spiral galaxy named ESO 137-001. This celestial cnidarian is shown here in beautiful detail. The various elements making up this image were captured by different telescopes. The galaxy and its surroundings were imaged by the NASA/ESA Hubble Space Telescope; its tails, which trace streams of hydrogen and show up in hues of bright purple, by the MUSE instrument mounted on the VLT; and bright hotspots of carbon oxide emission from within the system, which show up as flares of orange-red, were spotted by ALMA. These tails are caused by a dramatic phenomenon known as ram-pressure stripping. The space between galaxies in a cluster is not empty, but full of material that acts ...

23 September 2019: This week’s Picture of the Week showcases the bulging heart of the Milky Way as it hangs over the Chajnantor plateau. Located in the Atacama Desert of Chile, this plateau is one of the highest and driest places on Earth. This combination results in ideal conditions to observe millimetre and submillimetre radiation from space, which is usually strongly absorbed by Earth’s atmosphere. It is therefore no surprise that the Chajnantor plateau is home to the spectacularly productive Atacama Large Millimeter/submillimeter Array (ALMA), a state-of-the-art telescope that is studying light from some of the coldest objects in the Universe. Above the intricate dust clouds and the frenzied glow of billions of stars, Mars, Saturn and the star Antares make a distinct triangle in the sky. The fuzzy green object to the left of the frame, nearly drowned out by the spectacular light of the Milky Way, is an interplanetary visitor called ...

16 September 2019: From 4 to 18 August this year, AstroCamp 2019 took place at the Centre for Environmental Education and Interpretation in the Corno de Bico Protected Landscape in northern Portugal. AstroCamp is an astronomy-focused academic programme for secondary school students which aims to bring together students with different backgrounds and life experiences, but with one common passion: astronomy. 18 students aged between 15 and 18 took part in the camp — 11 girls and 7 boys, from Brazil, Germany, Italy, Poland, Portugal, Spain, Sweden and the United Kingdom. Over the course of two weeks, the astronomy enthusiasts took courses on relativity and on the physics of stars, galaxies and the Universe as a whole, observed the dark night skies using both the naked eye and telescopes, and connected online with astronomers and physicists from different countries. They also completed a computational project, working with data from some of the world’s best ...

9 September 2019: This beautiful image features the Milky Way rising over the Residencia at ESO’s Paranal Observatory, which can be seen atop a mountain in the distance. The Residencia is ESO’s private hotel for staff at Paranal, a home away from home for the astronomers, engineers, technicians, and other visitors to the site. Known as an “oasis for astronomers”, the building includes a restaurant, music room, library, swimming pool, and even a sauna to help astronomers to relax between and after their shifts. It was even featured in the James Bond film “Quantum of Solace” (2008). This photograph was taken by ESO Photo Ambassador Petr Horálek, and is a great demonstration of just how artificial light can pollute its environment — the brightness of the Residencia lights seems almost blinding compared to the stars. Artificial light scatters off the particles in our atmosphere and can drown out the night sky. Preserving the ...

2 September 2019: NGC 3351, also known as Messier 95, was first discovered in 1781 by Pierre Méchain, a French astronomer and surveyor who worked alongside Charles Messier. NGC 3351 is a type of galaxy known as a barred spiral galaxy and it is located in the constellation of Leo (The Lion). New observations of this object have shown stellar feedback in action. Stellar feedback is the process of redistributing energy into the interstellar medium (the space in between the stars) within star-forming galaxies. In this particular galaxy, star formation is occurring in the ring surrounding the galaxy nucleus at such a violent rate that massive bubbles of hot gas can actually be seen being ejected. This ejected gas can then contribute (both positively and negatively) to ongoing star formation within the galaxy. The data for this observation were taken with ALMA, the NASA/ESA Hubble Space Telescope and the Very Large Telescope, showing ...

26 August 2019: Snow is a rare sight at Paranal Observatory. However, when it does choose to appear, the remote Chilean landscape transforms into something quite extraordinary and otherworldly. The distant, snow-covered mountain at the centre of the frame is Cerro Paranal, the site of ESO’s Very Large Telescope (VLT). The VLT is made up of four large Unit Telescopes (UTs) — Antu, Kueyen, Melipal, and Yepun — and four smaller Auxiliary Telescopes (ATs). In this image the very tops of two of the UTs can be seen peeking over the mountaintop, alongside the VLT Survey Telescope (VST), which began observing in 2011. This image, taken by ESO Photo Ambassador Gerhard Hüdepohl, captures a truly rare view of Paranal. Precipitation of any kind is very rare in the Atacama Desert; the location is the driest non-polar desert in the world. Some parts of the Atacama have not experienced a single drop of rain ...

19 August 2019: The 12-metre dish of the Atacama Pathfinder Experiment (APEX) cuts a lonely figure in this aerial image of the Chajnantor Plateau in northern Chile (right of the centre). The snow visible in the background alludes to the frigid temperatures found at an altitude of over 5000 metres above sea level. This telescope is located in the arid, dry Atacama Desert, which experiences an average rainfall of only 100 millimetres per year. Since first light in 2004, APEX has contributed much to our understanding of the Universe at submillimetre wavelengths in the areas of star and planet formation, very distant galaxies in the early Universe, and the conditions present in molecular clouds. Among the many astronomical insights APEX has given us, it was the first telescope to detect hydrogen peroxide in space and the first to observe a circumstellar disc around a young massive star. APEX was created from a modified ...

12 August 2019: Thanks to the dark and clear conditions at ESO’s La Silla Observatory in Chile, capturing stunning images of the Milky Way is relatively commonplace for visiting photographers. However, despite the favourable conditions, producing beautiful and detailed images such as this is not easy — as ESO Photo Ambassador Petr Horálek discovered when taking this unusual photograph of the La Silla Observatory main building, which hosts the hotel, the canteen and other facilities. Petr took 52 individual shots to assemble this composite, moving and rearranging various pieces of furniture and himself — the coffee-drinking stargazer featured in the image — as he did so. Petr worked into the early hours, with only the low light of the corridor to disturb him. However, just as he prepared for the final few shots, all the chefs arrived, turning on a plethora of bright lights and ruining the photo. Petr had to return before ...

5 August 2019: The telescope in this eye-catching picture is appropriately named VISTA, short for the Visible and Infrared Survey Telescope for Astronomy. The telescope is located at ESO’s Paranal Observatory in Chile, where the altitude and arid climate make for cloudless skies and excellent viewing conditions. Different phenomena in the Universe produce different kinds of light, only a tiny fraction of which is visible to the human eye. VISTA observes infrared light, the same radiation that we can feel as heat. The three-tonne camera housed inside the telescope is extremely sensitive, allowing VISTA to detect this kind of light from very distant sources in the Universe and to produce both stunning images and groundbreaking scientific results. Enjoying the same exceptional skies as VISTA is another of ESO’s facilities, the Very Large Telescope (VLT), which can be just about be seen atop a distant peak. Despite the impressive size and ingenuity of these ...

29 July 2019: This spectacular portrait of the Centaurus A galaxy was captured under clear skies by the newest operational ESO observatory, SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars), located at the Paranal Observatory in Chile. The state of the art observatory is fitted an array of four one-metre telescopes, each named after one of the four Galilean moons. The SPECULOOS telescopes are neighbours of two of ESO’s most powerful telescopes, the Very Large Telescope (VLT) and VISTA. SPECULOOS is set to survey up to ten times more red dwarf stars than the TRAPPIST telescope (located at ESO La Silla Observatory) currently does. It is predicted statistically that it will then find at least twelve solar systems of a similar size to the now famous TRAPPIST-1 system. The Centaurus A galaxy (NGC 5128) is one of the brightest galaxies in the southern hemisphere night sky, located in the constellation of Centaurus. It ...

22 July 2019: The modern building in this image is the Residencia at ESO's Paranal Observatory in Chile, a home from home for the many professionals and technicians working at the observatory. Above the astronomers’ home in the Atacama Desert, the image shows the Milky Way galaxy — our home in the Universe. The Residencia was designed by the German architects Auer+Weber, and integrates perfectly into the arid landscape of the Atacama Desert in order to disturb astronomical observations as little as possible. The sandy colour and modern design of the building suit the Mars-like terrain around the observatory. The Residencia was chosen as the perfect hide-out for the Bond villain in the movie Quantum of Solace, and was blown up — only virtually — in one of the key scenes. Paranal Observatory hosts ESO's Very Large Telescope (VLT), as well as four Auxiliary Telescopes that can work together to form the Very ...

15 July 2019: This is SS 433, a microquasar first discovered forty years ago and located about 18 000 light-years away in the constellation of Aquila (The Eagle). This image, captured for the very first time at submillimeter wavelengths by the Atacama Large Millimeter/submillimeter Array (ALMA), is special because it shows the jets emitted by a hot, swirling disc of material encircling the black hole at SS 433’s centre. Owing to its relative proximity, SS 433 is a particularly useful object for researchers looking to learn more about microquasars and the jets they emit. The corkscrew shape visible here is created by a phenomenon known as precession; as they move outwards through space, these two jets are slowly tumbling around an axis in a similar way to the motion of a gyroscope or a spinning top slowing down, the orientation of their rotational axes changing as they do so. The scale of this ...

8 July 2019: This red-hued cloud of gas is named Abell 24, and is located in the constellation of Canis Minor (The Lesser Dog). It is something known as a planetary nebula — a burst of gas and dust created when a star dies and throws its outer layers into space. Despite the name, planetary nebulae have nothing to do with planets. The term was coined by William Herschel, who also famously discovered Uranus; in a time of low-resolution astronomy, these nebulous objects appeared to resemble giant planets swimming in a dark cosmos. A Sun-like star spends most of its life converting hydrogen into helium in its core. In its twilight years the star runs out of fuel and becomes unbalanced; it can no longer resist the inward crush of gravity and the core begins to collapse. The temperature in the core rises dramatically while the cooler outer layers expand, causing the entire ...

1 July 2019: Almost exactly 100 years ago, a remarkable event occurred: a total solar eclipse. This eclipse was special in more ways than one. Firstly, at just under seven minutes in duration, it was the longest such eclipse in over 500 years. Secondly, it was used by astronomers to explore the then-new theory of general relativity — with successful and groundbreaking results. Einstein published his general theory of relativity in 1915. The total solar eclipse of 1919 offered the perfect opportunity to test it experimentally, by exploring whether — and how — the immense gravity of the Sun bends and distorts incoming light from more distant stars, as predicted by Einstein’s theory. For a brief moment during the eclipse, the Moon would block the Sun’s light in the sky and make visible some of the stars that lie close to the line of sight of the Sun, not normally visible during the ...