Picture of the Week

14 October 2013

Surprise Cloud Around Vast Star

This new picture from the VLT Survey Telescope (VST) at ESO's Paranal Observatory shows the remarkable super star cluster Westerlund 1 (eso1034). This exceptionally bright cluster lies about 16 000 light-years from Earth in the southern constellation of Ara (The Altar). It contains hundreds of very massive and brilliant stars, all of which are just a few million years old — babies by stellar standards. But our view of this cluster is hampered by gas and dust that prevents most of the visible light from the cluster's stars from getting to Earth.

Now, astronomers studying images of Westerlund 1 from a new survey of the southern skies [1] have spotted something unexpected in this cluster. Around one of the stars — known as W26, a red supergiant and possibly the biggest star known— they have discovered clouds of glowing hydrogen gas, shown as green features in this new image.

Such glowing clouds around massive stars are very rare, and are even rarer around a red supergiant— this is the first ionised nebula discovered around such a star. W26 itself would be too cool to make the gas glow; the astronomers speculate that the source of the ionising radiation may be either hot blue stars elsewhere in the cluster, or possibly a fainter, but much hotter, companion star to W26.

W26 will eventually explode as a supernova. The nebula that surrounds it is very similar to the nebula surrounding SN1987A, the remnants of a star that went supernova in 1987 [2]. SN1987A was the closest observed supernova to Earth since 1604, and as such it gave astronomers a chance to explore the properties of these explosions. Studying objects like this new nebula around W26 will help astronomers to understand the mass loss processes around these massive stars, which eventually lead to their explosive demise.


[1] This picture forms part of a detailed public survey of a large part of the Milky Way called VPHAS+ that is using the power of the VST to search for new objects such as young stars and planetary nebulae. A spectacular recent picture of the Prawn Nebula was made using observations from the same survey.

[2] This nebula is thought to have surrounded SN1987A’s progenitor star since before it went supernova.


7 October 2013

An Oasis, or a Secret Lair?

This image shows a dark Chilean sky filled with spectacular star trails — caused by the Earth's rotation during the camera's long exposure time. Underneath these dramatic streaks lies the Paranal Residencia, an oasis to the staff and visitors to ESO's Very Large Telescope, located high on Cerro Paranal in the Chilean desert.

Construction of the Residencia began in 1998 and was completed by 2002. Since then, it has offered a welcome break from the harsh, dry climate of the desert to the scientists and engineers who work at Paranal Observatory.

The four-storey building has the majority of its structure buried underground. The facility was designed by German architects Auer+Weber to complement the surrounding environment. From certain angles, the combination of hi-tech utilitarian architecture and inconspicuous, almost camouflage-like design is reminiscent of a villain’s secret lair. Perhaps it is no surprise that the Residencia was selected as the setting for the final battle in the 2008 James Bond movie Quantum of Solace.

Flickr user John Colosimo submitted this photograph to the Your ESO Pictures Flickr group. The Flickr group is regularly reviewed and the best photos are selected to be featured in our popular Picture of the Week series, or in our gallery.


30 September 2013

Unveiling distant stars and galaxies

This frame, scattered with distant stars and galaxies, is a deep-field image taken using the Wide Field Imager (WFI), a camera mounted on the MPG/ESO 2.2-metre telescope located at the La Silla Observatory, Chile.

It was snapped as part of the COMBO-17 survey (Classifying Objects by Medium-Band Observations in 17 filters), a project that imaged five small patches of sky in 17 different coloured optical filters. The total area of sky explored in each of the COMBO-17 fields equates to approximately the same size as the full Moon, and has revealed huge numbers of distant objects — demonstrating just how much is still waiting to be discovered in our skies.

The image shows a region that was also investigated as part of the FORS Deep Field (FDF), a project that examined various areas of sky in great detail and depth using the FORS2 spectrograph instrument currently installed on ESO’s Very Large Telescope at the Paranal Observatory, Chile. However, these WFI images used many more filters than previous FDF observations, and looked at bigger patches of sky, resulting in images like the one above.

These small glimpses into the Universe have unveiled tens of thousands of distant stars, galaxies, and quasars previously hidden from our view, and have been used to investigate gravitational lensing and the distribution of dark matter in galaxies and clusters.


23 September 2013

New Cool Starlet in Our Backyard

This new image, from ESO’s VISTA telescope, shows a newly-discovered brown dwarf nicknamed VVV BD001, which is located at the very centre of this zoomable image. It is the first new brown dwarf spotted in our cosmic neighbourhood as part of the VVV Survey. VVV BD001 is located about 55 light-years away from us, towards the very crowded centre of our galaxy.

Brown dwarfs are stars that never quite managed to grow up into a star like our Sun. They are often referred to as “failed stars”; they are larger in size than planets like Jupiter, but smaller than stars.

This dwarf is peculiar in two ways; firstly, it is the first one found towards the centre of our Milky Way, one of the most crowded regions of the sky. Secondly, it belongs to an unusual class of stars known as “unusually blue brown dwarfs” — it is still unclear why these stars are bluer than expected.

Brown dwarfs are born in the same way as stars, but do not have enough mass to trigger the burning of hydrogen to become normal stars. Because of this they are much cooler and produce far less light, making them harder to find. Astronomers generally look for these objects using near and mid-infrared cameras and special telescopes that are sensitive to these very cool objects, but usually avoid looking in very crowded regions of space — such as the central region of our galaxy, for example.

VISTA (the Visible and Infrared Survey Telescope for Astronomy) is the world’s largest survey telescope and is located at ESO’s Paranal Observatory in Chile. It is performing six separate surveys of the sky, and the VVV (VISTA Variables in the Via Lactea) survey is designed to catalogue a billion objects in the centre of our own Milky Way galaxy. VVV BD001 was discovered by chance during this survey.

Scientists have used the VVV catalogue to create a 3 dimensional map of the central bulge of the Milky Way (eso1339). The data have also been used to create a monumental 108 200 by 81 500 pixel colour image containing nearly nine billion pixels (eso1242), one of the biggest astronomical images ever produced.


16 September 2013

Toconao Seen From Above

The small village of Toconao is the closest settlement to the largest astronomy project in existence, ALMA [1], the Atacama Large Millimeter/submillimeter Array. Toconao has less than 800 inhabitants and is located at 2475 metres above sea level in a natural oasis fed by a small mountain river on the outskirts of the driest desert in the world, the Atacama. The river doesn’t flow all year, but the local farmers have wisely built a network of dams and channels to regulate the flow of water so that they can have crops all year round.

When looking closely at this image, some buildings can be spotted, made of traditional materials such as adobe and volcanic rock, like the San Lucas Church and Bell Tower, on the bottom left of the image.

In parallel with their scientific work, ALMA staff have worked with the Atacameño Elders in Toconao and other areas to recover the vision of the Universe of their culture, aiming to preserve this cultural and scientific heritage for later generations.

ALMA has also been supporting an educational improvement plan at School E-21, a rural public education establishment in Toconao, since 2008. This plan, endorsed by the community, is focused on improving education in science and english.

This aerial image was taken by the two crew members of the ORA Wings for Science project, Clémentine Bacri and Adrien Normier, who flew a special eco-friendly ultralight aeroplane [2] on a year-long journey around the world to help out scientists, with aerial capabilities ranging from air sampling to archaeology, biodiversity observation and 3D terrain modelling.

ESO has an ongoing outreach partnership with this non-profit organisation. Short movies and amazing pictures that are produced during the flights will be used for educational purposes and for promoting local research. Their circumnavigation started in June 2012 and finished in June 2013 with a landing at the Paris Air Show.


[1] The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Southern Observatory (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

[2] The ultralight aircraft is a NASA-award winning Pipistrel Virus SW 80 using only 7 litres of fuel per 100 kilometres — less than most cars.

9 September 2013

Eyes over Cerro Armazones

This spectacular aerial shot of Cerro Armazones, taken by ESO Photo Ambassador Gerhard Hüdepohl, represents that wonderful moment for a photographer: when everything lines up for the perfect shot.

Hüdepohl captured this image while on a commercial flight from Antofagasta to Santiago. Shortly after taking off the plane took the ideal flight path for an aerial snap of Cerro Armazones — and Hüdepohl could not have asked for better conditions. Seizing the moment, he was able to capture this unusual perspective, high above the spectacular terrain.

This image shows the Atacama Desert with amazing clarity, with the thin, zigzag path standing out sharply from the dusty terrain. This dirt road can be seen slicing its way up to the summit of Cerro Armazones. The site will soon become the home of the European Extremely Large Telescope (E-ELT), a 39-metre telescope that will not only answer existing questions in astronomy, but also raise — and hopefully answer — entirely new questions altogether.


2 September 2013

PESSTO Snaps Supernova in Messier 74

ESO's PESSTO survey has captured this view of Messier 74, a stunning spiral galaxy with well-defined whirling arms. However, the real subject of this image is the galaxy's brilliant new addition from late July 2013: a Type II supernova named SN2013ej that is visible as the brightest star at the bottom left of the image.

Such supernovae occur when the core of a massive star collapses due to its own gravity at the end of its life. This collapse results in a massive explosion that ejects material far into space. The resulting detonation can be more brilliant than the entire galaxy that hosts it and can be visible to observers for weeks, or even months.

PESSTO (Public ESO Spectroscopic Survey for Transient Objects) is designed to study objects that appear briefly in the night sky, such as supernovae. It does this by utilising a number of instruments on the NTT (New Technology Telescope), located at ESO's La Silla Observatory in Chile. This new picture of SN2013ej was obtained using the NTT during the course of this survey.

SN2013ej is the third supernova to have been observed in Messier 74 since the turn of the millennium, the other two being SN 2002ap and SN 2003gd. It was first reported on 25 July 2013 by the KAIT telescope team in California, and the first "precovery image" was taken by amateur astronomer Christina Feliciano, who used the public access SLOOH Space Camera to look at the region in the days and hours immediately before the explosion.

Messier 74, in the constellation of Pisces (The Fish), is one of the most difficult Messier objects for amateur astronomers to spot due to its low surface brightness, but SN2013ej should still be visible to careful amateur astronomers over the next few weeks as a faint and fading star.


26 August 2013

Carved by Massive Stars

This image, captured by ESO’s Very Large Telescope (VLT) at Paranal, shows a small part of the well-known emission nebula, NGC 6357, located some 8000 light-years away, in the tail of the southern constellation of Scorpius (The Scorpion). The image glows with the characteristic red of an H II region, and contains a large amount of ionised and excited hydrogen gas.

The cloud is bathed in intense ultraviolet radiation — mainly from the open star cluster Pismis 24, home to some massive, young, blue stars — which it re-emits as visible light, in this distinctive red hue.

The cluster itself is out of the field of view of this picture, its diffuse light seen illuminating the cloud on the centre-right of the image. We are looking at a close-up of the surrounding nebula, showing a mesh of gas, dark dust, and newly born and still forming stars.

19 August 2013

Starry Night at La Silla

A piercingly bright curtain of stars is the backdrop for this beautiful image taken by astronomer Håkon Dahle. The silhouetted figure in the foreground is Håkon himself surrounded by just a couple of the great dark domes that litter the mountain of ESO’s La Silla Observatory.

Many professional astronomers are also keen photographers — and who could blame them? ESO sites in the Atacama Desert are among the best places on Earth for observing the stars, and for the same reason, are amazing places for photographing the night sky.

Håkon took these photos while on a week-long observing run at the MPG/ESO 2.2 -telescope. During this time, the telescope was occasionally handed over to a different observing team, giving Håkon the opportunity to admire the starry night — as well as to capture it for the rest of us to see.

The Milky Way is brighter in the Southern Hemisphere than in the North, because of the way our planet’s southern regions point towards the dense galactic centre. But even in the South, the Milky Way in the night sky is quite faint in the sky. For most of us, light pollution from our cities and even the Moon can outshine the faint glow of the galaxy, hiding it from view.

One of the best aspects of La Silla Observatory is that it is far away from bright city lights, giving it some of the darkest night skies on Earth. The atmosphere is also very clear, so there is no haze to further muddy your vision. The skies at La Silla are so dark that it is possible to see a shadow cast by the light of the Milky Way alone.

Håkon submitted this photograph to the Your ESO Pictures Flickr group. The Flickr group is regularly reviewed and the best photos are selected to be featured in our popular Picture of the Week series, or in our gallery.

12 August 2013

The calm before the storm

This beautiful image portrays the galaxies NGC 799 (below) and NGC 800 (above) located in the constellation of Cetus (The Whale). This pair of galaxies was first observed by the American astronomer Lewis Swift back in 1885.

Located at a distance of about 300 million light-years, our face-on view allows us to clearly appreciate their shapes. Like the Milky Way — our galaxy — these objects are both spiral galaxies, with characteristic long arms winding towards a bright bulge at the centre. In the prominent spiral arms, a large number of hot, young, blue stars are forming in clusters (tiny blue dots seen in the image) whereas in the central bulge a large group of cooler, redder, old stars are packed into a compact, almost spherical region.

At first glance, these galaxies look rather similar, but the devil is in the detail. Apart from the obvious difference in size, only NGC 799 has a bar structure, extending from its central bulge, and the spiral arms wind out from the ends of the bar. Galactic bars are thought to act as a mechanism that channels gas from the spiral arms to the centre, intensifying star formation. A supernova was also observed in NGC 799 in 2004, and was given the name SN2004dt.

Another interesting differentiating feature is the number of spiral arms. The small NGC 800 has three bright, knotty spiral arms, whilst NGC 799 only has two relatively dim, but broad spiral arms. These start at the end of the bar and wrap nearly completely around the galaxy forming a structure that looks almost like a ring.

While it might seem that this image depicts two impressive close spiral galaxies coexisting in an everlasting peace, nothing can be further than the truth. We could be just witnessing the calm before the storm. We don’t know exactly what the future will bring, but typically, when two galaxies are close enough, they interact over hundreds of millions of years by means of gravitational disturbances. In some cases, only minor interactions occur, causing shape distortions, but sometimes galaxies collide, merging to form a single, new and larger galaxy.

The image was obtained using the FORS1 instrument on the 8.2-metre ESO Very Large Telescope (VLT) atop Cerro Paranal, Chile. It combines exposures taken through three filters (B, V, R).

Five asteroids can also be seen — can you find them all? The asteroids moved between the different exposures leaving colourful streaks in the image.

5 August 2013

Belt of Venus over Cerro Paranal

This photo shows the view to the east from Paranal Observatory, seconds after the Sun has disappeared behind the horizon. The orange glow of the sunset can be seen against the 1.8-metre VLT Auxiliary Telescopes, and the almost full Moon is hanging in the sky. But the image is more interesting still, thanks to an atmospheric phenomenon known as the Belt of Venus.

The grey-bluish shadow above the horizon is the shadow of the Earth, and right above it is a pinkish glow. This phenomenon is produced by the reddened light of the setting Sun being backscattered by the Earth's atmosphere. As well as right after sunset, this atmospheric effect can also be seen shortly before sunrise. A very similar effect can also be observed during a total solar eclipse.

The telescopes shown in the image are three of the four 1.8-metre Auxiliary Telescopes, housed in ultra-compact mobile enclosures. These telescopes are dedicated to interferometric observations, when two or more telescopes work together, forming a virtual mirror and thus allowing astronomers to see much finer details than can be seen with the individual telescopes working independently.

Carolin Liefke took this photo during a visit to Paranal, and submitted it to the Your ESO Pictures Flickr group. The Flickr group is regularly reviewed and the best photos are selected to be featured in our popular Picture of the Week series, or in our gallery. Carolin works at the Haus der Astronomie (House of Astronomy) centre for astronomy education and outreach in Heidelberg, Germany, and is a member of the ESO Science Outreach Network (ESON). ESON brings ESO news to Member States and other countries by translating press releases and providing a point of contact for local media.


29 July 2013

Messier 100 — Grand Design Splendour

Spiral galaxies are usually very aesthetically appealing objects, and never more so than when they appear face-on. And this image is a particularly splendid example: it is the grand design spiral galaxy Messier 100, located in the southern part of the constellation of Coma Berenices, and lying about 55 million light-years from Earth.

While Messier 100 shows very well defined spiral arms, it also displays the faintest of bar-like structures in the centre, which classifies this as type SAB. Although it is not easily spotted in the image, scientists have been able to confirm the bar’s existence by observing it in other wavelengths.

This very detailed image shows the main features expected in a galaxy of this type: huge clouds of hydrogen gas, glowing in red patches when they re-emit the energy absorbed from newly born, massive stars; the uniform brightness of older, yellowish stars near the centre; and black shreds of dust weaving through the arms of the galaxy.

Messier 100 is one of the brightest members of the Virgo Cluster, which is the closest cluster of galaxies to our galaxy, the Milky Way, containing over 2000 galaxies, including spirals, ellipticals, and irregulars. This picture is a combination of images from the FORS instrument on ESO’s Very Large Telescope at Paranal Observatory in Chile, taken with red (R), green (V) and blue (B) filters.


22 July 2013

The NTT Spinning like a Top

This dynamic image shows the New Technology Telescope (NTT) located at ESO’s La Silla Observatory in Chile. The distinctively shaped enclosure of the telescope appears blurred by movement in the picture, as the telescope rotates to point at its desired target. The photo was taken with a 30-second exposure.

One of the first things you notice in this picture is that the telescope building has a peculiar angular shape on the outside, rather than the more common rounded dome design usually seen. Its design features have been much copied, including by ESO’s Very Large Telescope, but they were groundbreaking when the telescope was inaugurated in 1989.

The NTT’s revolutionary design targets optimal image quality, for instance, through carefully controlled ventilation, which optimises airflow across the NTT, minimising the blurring caused by air turbulence inside. Just visible in the blur of this image are the large flaps that form a key part of this system.

Another feature that was advanced at the time of its construction is the NTT’s mirror. While, at 3.58 metres in diameter, it was never considered particularly large, its design was highly innovative. The mirror is flexible, and can be adjusted in real time to maintain a perfect shape, so no flexing or sagging can harm the image quality. ESO and the NTT were pioneers in using this technology, called active optics, and it is now a standard feature of modern telescopes.

Currently, the NTT has two different instruments that astronomers can use to conduct their observations: SOFI (short for the Son of ISAAC, a VLT  instrument), which is an infrared spectrograph and imaging camera, and EFOSC2, a spectrograph and camera designed to detect faint objects.

The La Silla Observatory is located in the southern part of the Atacama Desert, 600 kilometres north of Santiago de Chile and at an altitude of 2400 metres. 

The image was taken by Malte Tewes, an astronomer at the Ecole Polytechnique Fédérale de Lausanne, Switzerland.

Malte submitted this photograph to the Your ESO Pictures Flickr group. The Flickr group is regularly reviewed and the best photos are selected to be featured in our popular Picture of the Week series, or in our gallery.


15 July 2013

Wings for Science Fly Over Paranal

This rare aerial view of the Paranal Observatory was taken in December 2012 by Clémentine Bacri and Adrien Normier, who are flying a special eco-friendly ultralight [1] aeroplane on a year-long journey around the world. This striking view shows the raw natural beauty of the landscape at the remote home of one of the world’s finest astronomical facilities, ESO’s Very Large Telescope (VLT), with its four independent 8.2-metre telescopes sitting at the top of Cerro Paranal.

ESO has an ongoing outreach partnership with the ORA Wings for Science project, a non-profit initiative which offers aerial support to public research organisations. The two crew members of the Wings for Science Project did a flyby above the observatories of Northern Chile, among other locations, before they left South America and jumped to Australia. During their trip, they help out scientists by providing aerial capabilities ranging from air sampling to archaeology, biodiversity observation and 3D terrain modelling.

The short movies and amazing pictures that are produced during the flights are used for educational purposes and for promoting local research. Their circumnavigation started in June 2012 and finished in June 2013 with a landing at the Paris Air Show on 17 June.


[1] The ultralight aircraft is a NASA-award winning Pipistrel Virus SW 80 using only 7 litres of fuel per 100 kilometres — less than most cars.



8 July 2013

Maëlle's New Toys

Astronomy and telescopes can sometimes bring out our inner child. In a testament to human curiosity, astronomers keep building ever-larger instruments in remote places throughout the world.

ESO Astronomer Julien Girard snapped this cute picture of his daughter during a family day at Paranal Observatory, in the Chilean Andes. Thanks to a trick of perspective, little Maëlle seems to be looking into the open dome of one of the 1.8-metre Auxiliary Telescopes of ESO’s Very Large Telescope (VLT). Although the telescopes are used for serious scientific research, astronomers can sometimes feel like children when playing with such giant “toys”.

Julien Girard is an ESO astronomer and an ESO Photo Ambassador based in Chile, working at the VLT. He is the instrument scientist for the NACO adaptive optics instrument on the VLT’s Unit Telescope 4. He submitted this photograph to the Your ESO Pictures Flickr group, from where it was picked out as an ESO Picture of the Week.


1 July 2013

European Antennas at ALMA’s Operations Support Facility

In this photograph from 2012, we see antennas destined to become part of the Atacama Large Millimeter/submillimeter Array (ALMA). The three antennas in the foreground, as well as some of those in the background, were supplied by ESO as part of its contribution to ALMA, through a contract with the European AEM Consortium [1]. In total ESO is providing 25 of the 12-metre-diameter antennas. A further twenty-five 12-metre antennas are provided by the North American ALMA partner, while the remainder, a set of twelve 7-metre and four 12-metre antennas comprising the Atacama Compact Array, are provided by the East Asian ALMA partner.

The antennas are seen here at ALMA’s Operations Support Facility (OSF), at an altitude of 2900 metres in the foothills of the Chilean Andes. Those in the foreground are in the AEM Site Erection Facility, where the antennas are assembled and rigorously tested before they are handed over to the observatory. The antennas in the background have been handed over, and are undergoing further tests or having their sensitive receivers installed. Once the antennas are ready, they are transported to the Array Operations Site, on the Chajnantor Plateau at an altitude of 5000 metres. There, they join their counterparts as part of the ALMA array, working to study some of the deepest questions of our cosmic origins. Even once all the antennas are ready, the OSF will remain the centre of activities for the daily operation of ALMA, as a workplace for astronomers and the teams responsible for maintaining the observatory.

On the horizon is the Andes mountain range, the tallest peak belonging to the conical volcano, Licancabur. Licancabur marks the border between Chile and Bolivia and dominates the landscape of the area.

ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.


[1] The AEM Consortium is composed of Thales Alenia Space, European Industrial Engineering, and MT-Mechatronics.


24 June 2013

Moonlight and Zodiacal Light Over La Silla

What may look like a futuristic city out of a science fiction story, floating high above the clouds, is ESO’s longest-serving observatory, La Silla. This photograph was taken by astronomer Alan Fitzsimmons while standing near the ESO 3.6-metre telescope just after sunset. The Moon is located just outside the frame of this picture, bathing the observatory in an eerie light that is reflected off the clouds below.

The very faint band of glowing golden light just above the clouds still illuminated by the sunset is the zodiacal light. It is caused by sunlight diffused by dust particles between the Sun and the planets. This can only be seen just after sunset or just before sunrise, at particular times of year, from very good sites.

Several telescopes can be seen in this photograph. For example, the large angular structure at the end of the road is the New Technology Telescope (NTT). True to its name, when completed in 1989 the telescope included a number of revolutionary features including being the first to use full active optics as well as a revolutionary octagonal enclosure. Many of the NTT’s features went on to be incorporated into ESO’s Very Large Telescope.

The dome in the foreground, just to the right is the Swiss 1.2-metre Leonhard Euler Telescope named in honour of the famous Swiss mathematician Leonhard Euler (1707–83).

Alan submitted this photograph to the Your ESO Pictures Flickr group. The Flickr group is regularly reviewed and the best photos are selected to be featured in our popular Picture of the Week series, or in our gallery.



17 June 2013

Thunderbolts and lightning

In this electrifying image, taken on Friday 7 June 2013, a furious thunderstorm is discharging its mighty rage over Cerro Paranal. The colossal enclosures of the four VLT Unit Telescopes, each one the size of an eight-storey building, are dwarfed under the hammering of the powerful storm.

In the left of the image, a solitary star has emerged to witness the show — a single point of light against an obscured sky. This star is Procyon, a bright binary star in the constellation of Canis Minor (The Lesser Dog).

Clouds over ESO’s Paranal Observatory are a rare sight. On average, the site experiences an astonishing 330 clear days every year. Lightning is even rarer, as the observatory is located in one of the driest places in the world: the Atacama Desert in Northern Chile, 2600 metres above sea level. If there are any clouds, most of the time the observatory stands above them.

Over a 16-year period working as an engineer on Paranal, ESO photo ambassador Gerhard Hüdepohl had seen lightning there just once before — so he grabbed his camera and ventured out into the elements to capture this unique sight.

10 June 2013

The Rise and Fall of a Supernova

An unusual new video sequence shows the rapid brightening and slower fading of a supernova explosion in the galaxy NGC 1365. The supernova, which has been named SN 2012fr, was discovered by French astronomer Alain Klotz on the 27 October 2012. The images captured by the small TAROT robotic telescope, located at ESO’s La Silla Observatory in Chile, have been compiled to create this unique movie.

Supernovae are the results of the explosive and cataclysmic deaths of certain types of stars. They are so brilliant that they can outshine their entire parent galaxy for many weeks before slowly fading from sight.

The supernova 2012fr [1] was discovered by Alain Klotz on the afternoon of 27 October 2012. He was busy measuring the brightness of a faint variable star in an image from the TAROT (Télescope à Action Rapide pour les Objets Transitoires) robotic telescope at ESO’s La Silla Observatory, when he noticed a new object that was not present in an image taken three days earlier. After checking with telescopes and astronomers all across the world the bright object was confirmed to be a Type Ia supernova.

Some stars co-habit with a second star, both orbiting around a common centre of gravity. In some cases one of them might be a very old white dwarf that is stealing material from its companion. At some point the white dwarf has siphoned off so much matter from its companion that it becomes unstable and explodes. This is known as a Type Ia supernova.

This kind of supernova has become very important as they are the most reliable way of measuring distances to very remote galaxies in the early Universe. Beyond the local group of galaxies, astronomers needed to find very bright objects with predictable properties that could act as signposts to help them map out the expansion history of the Universe. Type Ia supernovae are ideal as their brightnesses peak and fade in almost the same way for each explosion. Measurements of the distances to Type Ia supernovae led to the discovery of the accelerating expansion of the Universe, work that was awarded the Nobel Prize for Physics in 2011.

The host galaxy of this supernova is NGC 1365 (see also potw1037a), an elegant barred spiral galaxy, located 60 million light-years away towards the constellation of Fornax (The Furnace). With its diameter of about 200 000 light-years, it stands out among the other galaxies in the Fornax cluster. A colossal straight bar runs through the galaxy, containing the nucleus at the centre. The new supernova can be easily spotted just above the core, in the middle of the image.

Astronomers discovered more than 200 new supernovae in 2012, of which SN 2012fr is among the brightest. The supernova was first spotted when it was very faint on the 27 October 2012, and it reached its peak brightness on 11 November 2012 [2]. It was then easily seen as a faint star through a medium-sized amateur telescope. The video was compiled from a series of images taken of the galaxy over a period of three months, from the discovery in October until mid-January 2013.

TAROT is a 25-centimetre optical robotic telescope, able to move very fast, and to start an observation within a second. It was installed at La Silla Observatory in 2006 with the purpose of detecting cosmic gamma-ray bursts. The images that revealed SN 2012fr were captured using blue, green and red filters.


[1] Supernovae are designated by the year in which they are discovered, and the order in which they are discovered during that year, by using letters of the alphabet. The fact that the the supernova was discovered by a French team and it has been designated by the letters “fr” is pure coincidence.

[2] At this time it was magnitude 11.9. This is about 200 times too faint to see with the unaided eye even on a clear and dark night. But if the supernova at its peak brightness and our star the Sun were seen together at the same distance from the observer the supernova would appear about 3000 million times brighter than the Sun.



Alain Klotz
Institut de Recherche en Astrophysique et Planetologie
Toulouse, France
Tel: +33 05 61 55 66 66
Email: alain.klotz@irap.omp.eu

Richard Hook
ESO, La Silla, Paranal, E-ELT & Survey Telescopes Press Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

3 June 2013

Three Planets Dance Over La Silla

It’s a real treat for photographers and astronomers alike: our skies are currently witnessing a phenomenon known as a syzygy — when three celestial bodies (or more) nearly align themselves in the sky. When celestial bodies have similar ecliptic longitude, this event is also known as a triple near-conjunction. Of course, this is just a trick of perspective, but this doesn't make it any less spectacular. In this case, these bodies are three planets, and the only thing needed to enjoy the show is a clear view of the sky at sunset.

Luckily, this is what happened for ESO photo ambassador Yuri Beletsky, who had the chance to spot this spectacular view from ESO's La Silla Observatory in northern Chile on Sunday 26 May. Above the round domes of the telescopes, three of the planets in our Solar System — Jupiter (top), Venus (lower left), and Mercury (lower right) — were revealed after sunset, engaged in their cosmic dance.

An alignment like this happens only once every few years. The last one took place in May 2011, and the next one will not be until October 2015. This celestial triangle was at its best over the last week of May, but you may still be able to catch a glimpse of the three planets as they form ever-changing arrangements during their journey across the sky.


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