Picture of the Week

20 March 2017: This image, taken by the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, shows glowing dust inside the protocluster NGC 6334I. Studying this star-forming cloud in the Cat’s Paw Nebula (NGC 6334) with both ALMA and the Submillimeter Array (SMA) in Hawaii astronomers could see that something dramatic had taken place, completely changing a stellar nursery over a surprisingly short period of time. It is known that young stars form inside protoclusters when pockets of gas become so dense that they begin to collapse under their own gravity. Over time, discs of dust and gas form around these nascent stars and funnel material onto their surfaces helping them grow. However, this new image from ALMA shows a massive protostar, nestled deep within this dust-filled stellar nursery, that is undergoing an intense growth spurt, most likely triggered by an avalanche of gas falling onto its surface. This new material feeding it is ...

13 March 2017: With their spectacular glowing arms, grand spiral galaxies seem to get all the attention — but NGC 6822, a barred irregular dwarf galaxy, proves that regular spirals do not have a monopoly on galactic beauty. Also called Barnard’s galaxy, NGC 6822 is located in the constellation of Sagittarius just 1.6 million light-years away and is brimming with rich star formation regions. This new image is a composite of older observations made with the Wide Field Imager attached to the 2.2-metre MPG/ESO telescope at ESO’s La Silla Observatory and new data collected by the Atacama Large Millimeter/submillimeter Array (ALMA). The areas observed with ALMA are highlighted in the image and can be seen here in detail. The observations by ALMA reveal the structure of star-forming gas clouds in unprecedented resolution. Observations in our own galaxy have shown that stars form in the dense cores of giant clouds of molecular hydrogen gas, ...

6 March 2017: Although it looks like the pattern of a shell on the beach, this intriguing spiral is in fact astronomical in nature. The Atacama Large Millimeter/submillimeter Array (ALMA) captured this remarkable image of a binary star system, where two stars — LL Pegasi and its companion — are locked in a stellar waltz, orbiting around their common centre of gravity. The old star LL Pegasi is continuously losing gaseous material as it evolves into a planetary nebula, and the distinct spiral shape is the imprint made by the stars orbiting in this gas. The spiral spans light-years and winds around with extraordinary regularity. Based on the expansion rate of the spiralling gas, astronomers estimate that a new “layer” appears every 800 years — approximately the same time it takes for the two stars to complete one orbit around each other. LL Pegasi was first highlighted about 10 years ago when the ...

27 February 2017: Three decades ago, astronomers spotted one of the brightest supernovae in more than 400 years. The stellar explosion, SN 1987A, blazed with the power of 100 million suns for several months after its discovery on 23 February 1987. Located in the Large Magellanic Cloud, one of the Milky Way’s satellite galaxies, SN 1987A was the nearest supernova explosion observed in centuries and it quickly became the best studied supernova of all time. Over the last thirty years, detailed follow-up observations with telescopes both in space and on the ground have allowed astronomers to study the death throes of a massive star in unprecedented detail, from star to supernova to supernova remnant, revolutionising our understanding of these explosive events. With its superb sensitivity at millimetre and submillimetre wavelengths, the Atacama Large Millimeter/submillimeter Array (ALMA) has been exploring previously unstudied aspects of SN 1987A since 2013. Astronomers are using ALMA to observe ...

20 February 2017: The events surrounding the Big Bang were so cataclysmic that they left an indelible imprint on the fabric of the cosmos. We can detect these scars today by observing the oldest light in the Universe. As it was created nearly 14 billion years ago, this light — which exists now as weak microwave radiation and is thus named the cosmic microwave background (CMB) — has now expanded to permeate the entire cosmos, filling it with detectable photons. The CMB can be used to probe the cosmos via something known as the Sunyaev-Zel’dovich (SZ) effect, which was first observed over 30 years ago. We detect the CMB here on Earth when its constituent microwave photons travel to us through space. On their journey to us, they can pass through galaxy clusters that contain high-energy electrons. These electrons give the photons a tiny boost of energy. Detecting these boosted photons through our ...

13 February 2017: The sky is full of optical phenomena that can make it tricky to get a clear view of the cosmos. These present a frustrating challenge to astronomers, but for astrophotographers they can provide a real feast for the eyes! This stunning image shows the centre of the Milky Way crossed by the eerie glow of zodiacal light, and is full of dust-induced features that obstruct scientific observations — but they look so beautiful it’s difficult to mind too much. In this image, the centre of the Milky Way appears to be full of inky black gas. In fact, the dark swirling patches are simply the absence of visible light, because huge clouds of dust are obscuring the light from more distant stars. However, just as dust can give the illusion of darkness, it can also give the illusion of light. This is the case with zodiacal light, a fuzzy band ...

6 February 2017: Over 75 million light-years away in the constellation of Virgo (The Virgin) lies NGC 4981 — a spiral galaxy with a rather explosive past. NGC 4981 was discovered on 17 April 1784 by William Herschel, and subsequently documented in John Dreyer’s New General Catalogue. Over a century later, on 23 April 1968, the galaxy once again made it into the records when a Type la supernova — a stellar explosion in a binary star system — occurred within its confines: SN 1968I. SN 1968I, however, was not to be the galaxy’s only supernova. Decades later, the core collapse of a massive star led to supernova SN 2007c. This spectacular shot of NGC 4981 — not showing any of the supernovae explosions; the bright star visible in the image is a foreground star — was captured by FORS, the visible and near-UV FOcal Reducer and low dispersion Spectrograph for ESO’s Very ...

30 January 2017: This picture shows the ESO 3.6-metre telescope, located at the La Silla Observatory in Chile. The night sky overhead is dominated by the Moon, which shines so brightly that illuminates the scene fully. The most dominant feature of this image is the red rock in the foreground. It is marked with prehistoric engravings — signatures from the region’s past. Several such engravings can be found around La Silla, but this particular rock is part of the richest site in the area. A complete photographic and topographic survey of these engravings was carried out in 1990. The carved rocks predominantly depict scenes involving men and animals, as well as mysterious geometrical figures. It is believed that these engravings originate from the El Molle complex — the first culture in the north of Chile. Geologists believe that the first millennium of our era experienced a lot more rainfall than it does today, ...

23 January 2017: Here we see the crescent Moon rising over the serene Residencia at ESO’s Paranal Observatory. Next to the Moon Venus, the morning star, is also visible in the sky, and an array of ESO telescopes, now quiet after a night of observing, can be seen in the distance. While too small to be seen on this image, Venus has different phases, similar to those of the Moon. We see Venus as a disc when Venus is creeping around the back of the Sun as seen from Earth — the Sun’s rays hit the face of Venus that is facing the Earth, and the image of this full face is reflected back to us. The crescent phase occurs when Venus emerges from behind the Sun into the part of its orbit that lies between the Earth and the Sun and progressively less of the surface is directly illuminated as seen from ...

16 January 2017: Don’t be fooled! This isn’t a futuristic new Mars rover — though the harsh terrain of the Chilean Atacama Desert could easily be mistaken for Mars. This 20-metre-long, 10-metre-wide and 28-wheeled vehicle is an ALMA transporter known as Otto, pictured bathing beneath the beauty of the Milky Way! This mammoth machine was built in Germany. It was specially designed to transport ALMA antennas from the Operations Support Facility, located at 2900 metres above sea level, up to the Chajnantor Plateau, a site some 5000 metres above sea level and to move the antennas between the different available positions. Otto tips the scales at 130 tonnes, and can clock a top speed of 12 kilometres per hour while carrying an antenna — it certainly won’t be breaking any land speed records! Luckily, speed is not the priority during this delicate process. Safety and precision are paramount. Despite its bulk and power, ...

9 January 2017: The latest ESO Astronomy Camp explored the theme of The Visible and Hidden Universe. ESO and its Science Outreach Network collaborated with the science education event organiser Sterrenlab and the Astronomical Observatory of the Autonomous Region of the Aosta Valley (OAVdA) to arrange this fourth ESO Astronomy Camp on the topic of the multiwavelength universe. The camp took place from 26 December 2016 to 1 January 2017 in the Aosta Valley, Italy. In the course of the week the participants — young astronomy enthusiasts aged between 16 and 18 from different ESO member states — listened to lectures and performed hands-on activities and even night-time observations with the telescopes and instruments at the observatory. Social activities, winter sports and excursions contributed to making the camp a memorable experience for the participants. Some highlights from this year’s programme included: use of a spectrograph, lectures from ESO astronomers and an excursion to ...

2 January 2017: The skies over the Chilean Andes are never boring — not even when a soufflé, billow, flock, scud, or cover of clouds pays a rare visit! This image of the plateau at Chajnantor, 5000 metres above sea level, and home to the 66 antennas comprising the ALMA Observatory, shows strong winds and thick cloud approaching at sunset, resulting in an amazingly dramatic and fiery scene. ALMA is the Atacama Large Millimeter/submillimeter Array, a state-of-the-art observatory that studies a completely different kind of cloud to those captured here. Astronomers use ALMA to study molecular clouds, vast accumulations of gas and dust, at temperatures only a few tens of degrees above absolute zero. Often these star-forming regions are dark and obscured in visible light, but they shine brightly in the millimetre and submillimetre parts of the spectrum. This moment was captured by ESO Photo Ambassador Babak Tafreshi while he was participating in ...

26 December 2016: Our Solar System formed out of a huge, primordial cloud of gas and dust. The vast majority of that cloud formed the Sun, while the leftover disc of rotating material around it eventually coalesced into the orbiting planets we know — and live on — today. Astronomers can observe similar processes happening around other stars in the cosmos. This splendid Picture of the Week shows a disc of rotating, leftover material surrounding the young star HD 163296. Using the observing power of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, astronomers have been able to discern specific features in the disc, including concentric rings of material surrounding the central star. They were even able to use ALMA to obtain high-resolution measurements of the gas and dust constituents of the disc. With these data they could infer key details of the formation history of this young stellar system. The three gaps ...

19 December 2016: Season’s Greetings on behalf of everyone at the European Southern Observatory! We wish you happy holidays, a great start to the new year, and a fruitful 2017! Links: Christmas card 2016

12 December 2016: This stunning aerial image shows the hills and mountains surrounding ESO’s Paranal Observatory in Chile. From above, the sharp, rocky details of the arid landscape melt away, giving way to textures more akin to softly rippling fabric. The cluster of buildings in the top right of the frame contains both the observatory’s basecamp and the Residencia, where the staff and visitors to Paranal can seek refuge from the harsh desert conditions. The solitary buildings to the left of the main observatory complex house the VISTA survey telescope. This image was taken by Gerhard Hüdepohl, one of ESO’s Photo Ambassadors. He works for ESO as an electronics engineer and has lived in Chile since 1997, where he works at the Very Large Telescope on Cerro Paranal.

5 December 2016: The most massive galaxies in the Universe host supermassive black holes at their centres. These truly colossal black holes chew up surrounding material at astonishing rates, expelling huge amounts of radiation as they do so and glowing as some of the brightest objects in the known Universe! Despite their incredible distances from Earth, the regions surrounding these black holes shine so brightly that their appearance is similar to that of stars in our own galaxy, the Milky Way. Some of these objects, known as quasi-stellar-objects or quasars for short, are useful tools to help us better understand the cosmos. Because they lie so far away, there is plenty of intervening space between our telescopes and a target quasar. This space is not empty; it is filled with intergalactic medium, which mostly comprises clouds of gas — mainly hydrogen and helium, but also with hints of other elements — that absorb ...

28 November 2016: The famously dry Atacama Desert may seem like an odd place for the Moon to take a dip — but in this intriguing image, taken by ESO Photo Ambassador Petr Horálek, it appears to do just that! Initially high, the crescent Moon slowly descends through the clear Chilean sky, before hitting the thickest parts of the atmosphere right above the horizon. It was here that a “rare theatre” began, said Horálek. The thin sliver of the Moon was optically distorted into a “weird, snaky shape” as its light passed through layers of different air densities, caused by different pressures, temperatures and humidities. The Moon lost its smooth curves and instead appeared as a rippling and squiggly zig-zag — “as if it were swimming”. The effect of the closely spaced layers in the atmosphere caused different parts of the Moon’s image to be refracted differently as it disappeared below the horizon. ...

21 November 2016: As the Sun sets on another day at La Silla, the observatory’s staff members are able to start doing what they do best — observing and exploring the night sky! La Silla was ESO’s first observatory, and remains one of the most productive observatories in the world. This photograph captures the last few rays of sunlight, producing a striking blend of orange, red and yellow close to the horizon. More prominent, however, are the bright star trails streaking and curving through the sky. Each of these trails is formed by the motion of an individual star, captured over a long exposure time. Vehicles also form light trails from their rear headlights as they move, lighting up the network of roads throughout the region. This picture was taken by ESO Photo Ambassador Roger Wesson. To show both twilight and the growing star trails in the same image, Wesson combined 763 different ...

14 November 2016: The Atacama Large Millimeter/submillimeter Array (ALMA) sits high up on the Chajnantor Plateau in Chile. Construction of ALMA began in 2008, and the array saw first light in 2011. Up to now the astronomers, engineers, and technicians working at the site have had to live in temporary containers located at the facility’s basecamp. They will be pleased to hear that this situation will soon be coming to an end, as construction of the new ALMA Residencia reaches its final stages. Once all of ALMA’s antennas were successfully installed on the plateau, work began on the Residencia in early 2015. Located at the Operations Support Facility (OSF) at an altitude of 3000 metres, it is around 30 kilometres away from and over 2000 metres lower than ALMA, which resides in the Andes mountains at an altitude of 5000 metres. The OSF serves as the main basecamp for ALMA, coordinating all of ...

7 November 2016: Astronomers spend their time gazing out into the Universe — and occasionally the Universe seems to peer right back! This image, a composite of data from the Atacama Large Millimeter/submillimeter Array (ALMA) and the NASA/ESA Hubble Space Telescope, shows a very rare cosmic sight: a pair of interacting galaxies that have taken on an ocular structure. As the name suggests, some types of grazing encounters between galaxies create shapes that resemble the human eye. While galaxy collisions of this type are not uncommon, only a few galaxies with eye-like, or ocular, structures have been observed. The paucity of these features is likely due to their very ephemeral nature — ocular structures like these tend to only last for several tens of millions of years, which is merely the blink of an eye in a galactic lifetime. These two galaxies are named IC 2163 (left) and NGC 2207 (right) — IC ...