Picture of the Week

7 April 2014

Cosmic Fireball Falling Over ALMA

This beautiful new image, taken during a time-lapse set at the Atacama Large Millimeter/submillimeter Array (ALMA) is another dramatic Ultra High Definition photograph from the ESO Ultra HD Expedition. ALMA, located at 5000 metres above sea level on the remote and empty Chajnantor Plateau in the Chilean Andes, marks the second destination for the four ESO Photo Ambassadors [1] on their 17-day trip. The ambassadors are equipped with state-of-the-art Ultra HD tools to help them capture the true majesty of sights like the one pictured here [2] [3].

Some of the 66 high-precision antennas that comprise ALMA are visible here, with dishes pointed aloft, studying the cold clouds in interstellar space, and peering deep into the past at our mysterious cosmic origins.

The spectacular javelin of light over the ALMA array is a shooting star, slicing through the image in a vivid streak of colours. Emerald green, golden and faint crimson hues blaze brightly as the meteor burns up as it enters the Earth’s atmosphere and makes its fiery voyage across the sky. As the high-speed fireball — which is, in reality, a small grain of rock from interplanetary space — interacts with the atmosphere it heats up, vapourising the surface layers of the meteor, which are left behind in a glowing trail. These trails disappear in just a few seconds, but are captured here at the click of a button.

The brightest star in the constellation of Virgo (The Virgin), known as Spica, and our neighbouring planet Mars glow brightly in the centre of the image — cosmic spectators to this fiery descent as they rise above the horizon.

The Ultra HD Expedition began in Santiago, Chile, on 25 March 2014. This image was taken on the team’s eighth night on the Chajnantor Plateau. They are currently at La Silla Observatory, ESO’s first astronomical installation in Chile, and tomorrow, after one last night, they will finally make the long journey home. Free Ultra HD content gained from this expedition will soon be available online as ESO delivers crisp, breathtaking Ultra HD footage — bringing the Universe closer than ever before. This image was taken by ESO Photo Ambassador and time-lapse Cinematographer Christoph Malin.


[1] The team is made up of ESO’s videographer Herbert Zodet, and three ESO Photo Ambassadors: Yuri Beletsky, Christoph Malin and Babak Tafreshi. Information on the expedition’s technology partners can be found here, and their blog here.

[2] Equipment includes: Vixen Optics Polarie Star Tracker, Canon® EOS-1D C camera, Stage One Dolly and eMotimo TB3 3-axis motion control camera robot, Angelbird SSD2go, LRTimelapse software. Peli™ Cases, 4K PC workstations from Magic Multimedia, Novoflex QuadroPod system, Intecro batteries and Granite Bay Software.

[3] Technology partners include: Canon, Kids of All Ages, Novoflex, Angelbird, Sharp, Vixen, eMotimo, Peli, Magic Multi Media, LRTimelapse, Intecro and Granite Bay Software.

24 March 2014

Framing the Night Sky

ESO's observatories are privileged spots where astrophotographers can catch amazing views of the cosmos. But that's not all — sometimes, they are ideal locations from which to capture otherworldly images of our own planet, too. In this shot, ESO photo ambassador Gabriel Brammer has used a fish-eye lens to create this spectacular round effect. The clear sky over Paranal looks like a glass ball full of stars, with the Very Large Telescope (VLT) platform framing the picture.

In the bottom left the four VLT Unit Telescopes, each some 25 metres tall, are observing the night sky, one of them pointing its laser up into the night. Scattered around the top left of the frame, the round domes of the VLT Auxiliary Telescopes are easily spotted under the bright Milky Way. The two blurry smudges just above the laser are the Large and Small Magellanic Clouds, two of the closest galaxies to our own.

This image is created from a number of different wide-angle pictures, stitched together to show the complete view.

17 March 2014

A Milky Arc Over Paranal

Another clear night at ESO’s Paranal Observatory in Chile — perfect for sitting back and taking in the sight of our galaxy, the Milky Way. Many of us living in living in crowded, light-polluted cities no longer get to see our cosmic home in such detail.

We now know this stunning view to be our home galaxy, but the Ancient Greeks thought that it was the work of the Gods. Their legends told that this cloudy streak across the sky was really the breast milk of Hera, wife of Zeus. The Ancient Greeks are also to thank for the name “Milky Way”. The Hellenistic phrase Γαλαξίας κύκλος, pronounced galaxias kyklos, means “milky circle”, and provides the root for our modern name.

This 360 degree panorama image was taken by ESO Photo Ambassador Gabriel Brammer. An astronomer visiting Paranal can be seen standing towards the right hand side of this image admiring the view.

10 March 2014

Rosetta’s Comet is Waking Up

On 20 January 2014, ESA's Rosetta spacecraft emerged from a long deep-space hibernation to approach its target — comet 67P/Churyumov-Gerasimenko (67P/CG).

From our vantage point on Earth, comet 67P/CG has only just reappeared from behind the Sun. On 28 February 2014 ESO's Very Large Telescope (VLT) directed its gaze towards the comet as soon as it became visible from ESO's Paranal Observatory in Chile. ESO is collaborating with ESA to monitor the comet from the ground as it is approached by Rosetta over the coming months. These observations will prepare for the spacecraft's major rendezvous with the comet, planned for August of this year (see potw1403a).

This new image, and many more to come, will be used by ESA to refine Rosetta's navigation, and to monitor how much dust the comet is releasing. The image on the left was created by stacking the individual exposures to show the background stars — they were then shifted to compensate for the motion of the comet, which appears as a small dot right on top of one of the star trails (at the centre of the circle). The image on the right shows the comet with the stars subtracted out.

This new image shows a brightening of the comet, indicating that the ice at its heart has started to evaporate as it warms up in its approach to the Sun. Just like the Rosetta spacecraft, the comet itself is emerging from hibernation.


3 March 2014

ALMA Workers Rescue Abandoned Vicuña Fawn

High on the Chajnantor Plateau in the Chilean Andes lies the Atacama Large Millimeter/submillimeter Array (ALMA), an observatory surrounded by large expanses of dry landscape. Perhaps surprisingly, the region is home to a number of different wildlife species, many of which occasionally pop up near to the observatory. Further south, ESO’s La Silla Observatory recently had visits from a South American grey fox (potw1406a), and wild horses (potw1344a).

The most recent cute visitor to ALMA is this vicuña fawn, found on 16 February 2014 by ALMA workers. The fawn was only a few weeks old, weakened after it was chased by foxes until it lost sight of its herd.

After a couple of unsuccessful attempts the following day to return the fawn to its herd, the workers transferred it to the Wildlife Rescue and Rehabilitation Center at the Universidad de Antofagasta, where it is being treated so that it can eventually be released on the Andean plateau approximately one year from now.

24 February 2014

The Curves of ESO’s Headquarters

Bereft of colour in this striking infrared image, the sweeping curves of ESO's Headquarters clash with the frosty natural beauty of the surrounding trees. The extreme curvature visible in this image is due to the photographer's use of a fisheye lens, which distorts the view and causes the building to encircle the pale foliage and frame the sky above. The foliage appears to be bright as it reflects the infrared light, and the pale white hue comes from the photographer applying a white colour balance to the tree leaves.

The precise curves of concrete, glass, and steel give clues as to the Headquarters building's peculiar structure. In 1981 an article in ESO's The Messenger described the ESO building as "a labyrinth of the kind used to test the intelligence of rats". But, fortunately for ESO, the writer soon noted that "human beings are on average cleverer than rats, and the problem is quickly solved".

This image was taken by ESO computer specialist Dirk Essl.

17 February 2014

VST Snaps Gaia en Route to a Billion Stars

These new images from ESO's Very Large Telescope Survey Telescope (VST) show ESA's Gaia spacecraft in its position some 1.5 million kilometres beyond Earth's orbit.

Launched on the morning of Thursday, 19 December 2013, the satellite is on a quest to build a 3D map of our galaxy over the next five years. Mapping the sky has been one of humanity's quests since the dawn of time, and Gaia will take our understanding of our stellar neighbourhood to a whole new level. It will measure very precisely the positions and motions of about one billion stars in our galaxy, to explore the Milky Way's composition, formation and evolution.

These new observations are the result of a close collaboration between ESA and ESO to monitor the spacecraft from the ground. Gaia is the most accurate astrometric device ever built, but in order for its observations to be useful it needs to know exactly where it is in the Universe. The only way to know the velocity and position of the spacecraft with very high precision is to observe it on a daily basis from the ground — using telescopes including ESO's VST in a campaign known as Ground-Based Optical Tracking, or GBOT.

The VST is a state-of-the-art 2.6-metre telescope equipped with OmegaCAM, a monster 268-megapixel CCD camera with a field of view four times the area of the full Moon. The VST captured these images using OmegaCAM on 23 January 2014, taken about 6.5 minutes apart. Gaia is clearly visible as a small spot moving against a background of stars. Its location is circled in red. In these images, the spacecraft is about a million times fainter than is detectable by the naked eye.

Gaia was previously observed in December 2013 by the VST, very soon after its launch — it is one of the closest objects ever observed by the VST. It appeared in precisely the location expected, highlighting a successful collaboration between ground- and space-based astronomy!


10 February 2014

Fantastic Mr Fox

Perched precariously on the edge of the habitable world, life manages to cling on. On the outskirts of the hot, dry Atacama Desert, this hardy South American grey fox has just awoken, stretching leisurely. These foxes are generally active during the night, making the most of the drop in temperature that comes with a respite from the hot Chilean Sun.

In the background there are other signs of life. This white dome houses the Swiss 1.2-metre Leonhard Euler Telescope, which is protected from the harsh conditions by its outer shell. As the skies grow darker at ESO’s La Silla Observatory another famously nocturnal species, the astronomer, wakes up, stretches, and gets ready to scan the skies with buzzing and whirring technology.

This image was taken by ESO Photo Ambassador Malte Tewes and submitted 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.


3 February 2014

Antarctic Air Visits Paranal

This beautiful panorama of ESO's Paranal Observatory was taken on 5 July 2012, and marks one of the driest days ever recorded at the Very Large Telescope complex. Paranal sits like an island in the middle of the frame, with massive cloud banks floating below, over the distant Pacific Ocean.

The extremely low humidity at Paranal during this period was recorded by a water vapour radiometer known as LHATPRO, which monitors the atmosphere to support the observations carried out at the observatory [1]. Meteorologists from two Chilean universities identified the cause for these unusually dry conditions: high-altitude Antarctic air moving far to the north, and descending over Paranal.

This cold front lingered around Paranal for over 12 hours, causing a record-low level of humidity in the air above the observatory [2]. Florian Kerber (ESO) and colleagues analysed this unusual weather, publishing the results in a paper in the Monthly Notices of the Royal Astronomical Society on 29 January 2014, available here.

So, a dry desert… what is so special about that? Well, dryness of this magnitude is normally experienced at much higher altitudes, for example at the ALMA Observatory on the Chajnantor Plateau, which is located at 5000 metres above sea level — at 2635 metres, the altitude of Paranal is around half of this. Given that infrared observations can be best taken when there is little water vapour in the air, this could mean that routine monitoring using the LHATPRO radiometer will give astronomers the opportunity to exploit future dry spells at Paranal, to obtain great infrared observations of the Universe around us.

The photo was taken by ESO photo ambassador Gabriel Brammer, who coincidentally experienced the sunset that immediately preceded this dry spell, and found it to be extraordinarily clear and beautiful. Gabriel works as an astronomer at the ESO La Silla-Paranal Observatory. When not supporting the operations of the observatory, he studies the formation and evolution of distant galaxies using the most sophisticated telescopes and instrumentation in the world, including the ESO Very Large Telescope and the Hubble Space Telescope.


[1] The Low Humidity and Temperature Profiling radiometer (LHATPRO), manufactured by Radiometer Physics GmbH in Germany, uses strong spectral lines from certain elements to measure the water content of the atmosphere.

[2] The humidity is measured in the form of precipitable water vapour — a measure of atmospheric water content. It is the amount of water in a column of the atmosphere if it were all to fall as rain. In this case only 0.1 mm of precipitable water vapour was measured — much less than the usual (but already low) figure of 2 mm at Paranal.

20 January 2014

Rosetta's Comet

ESA's Rosetta spacecraft will wake up today, 20 January, after 31 months in deep space hibernation, to finally close in on comet 67P/Churyumov-Gerasimenko (67P/CG).

This image shows the most recent observations of the 4-kilometre diameter comet, taken on 5 October 2013 by ESO's Very Large Telescope (VLT) when the comet was around 500 million kilometres away — before it passed behind the Sun and out of view from Earth's perspective.

For this image, a long series of observations was processed to reveal both the comet without the background stars (on the left panel), and the star field with the track of the comet marked (on the right). Viewed against a crowded star field towards the centre of the Milky Way, the comet was still so far from the Sun that the icy nucleus was not releasing any gas or dust, and appears as a simple spot. As it approaches the Sun, its surface will heat up and its ices will sublimate, dragging dust out to form a tail.

The observation marks the start of a close collaboration between ESA and ESO to monitor the comet from the ground during Rosetta's encounter with 67P/CG later this year. Rosetta was launched in 2004 and aims to explore the surface of the comet, deploying a lander down onto 67P/CG to see what its surface is like [1].

The comet is on a 6.5-year orbit around the Sun and is currently out towards the orbit of Jupiter. It will be closest to the Sun — roughly between the orbits of Earth and Mars — in August 2015. This image suggests that the comet is not yet active, so scientists will be keen to check in on the comet again in February, when it is next observable by the VLT, and much closer to the Sun.

In the meantime, the observations carried out in October have been used to confirm the comet's orbit ahead of the major rendezvous manoeuvre planned for Rosetta in May, to line it up for orbiting 67P/CG in August. Further calculations will be made once Rosetta sights the comet in its own imaging system.


[1] Since its launch, Rosetta has travelled around the Sun five times, picking up speed and aligning itself with its final destination. For the coldest leg of the mission, as Rosetta ventured out beyond the orbit of Jupiter, the spacecraft was put into deep-space hibernation. 67P/CG is on a reasonably stable and well-known orbit, meaning that calculations for Rosetta's trajectory could be made far in advance of the spacecraft's launch, and it is far enough away from the Sun to make it a safe target.


13 January 2014

ALMA and Chajnantor at Twilight

Thanks to ESO’s Photo Ambassadors we can enjoy sensational images taken at the ESO sites on the remote mountaintops of Chile. Babak Tafreshi has captured this fine panoramic view of the antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) at twilight. Resembling a frame from a science fiction movie, the technological spectacle of ALMA against the raw natural power of the landscape on the Chajnantor Plateau, 5000 metres above sea level, results in fascinating images like this one.

There are a few details you shouldn't miss in this panoramic photo of ALMA (seen more clearly in the zoomable version), all lying between the two groups of antennas: the "Earth's shadow" and "Belt of Venus" phenomena, visible as the dark blue and light pink bands stretching across the sky, and the planet Jupiter, seen right above the mountain in the background.

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.

6 January 2014

Paranal Nights

Gaze up at the night sky from ESO's Paranal Observatory in Chile, and you will be greeted with a stunning view like this one. Flecks of blue, orange, red; each a different star, galaxy, nebula, or more, together forming a sparkling sky overhead. Astronomers peer at this beautiful backdrop, trying to unravel the mysteries of the Universe.

To do this, they use telescopes like the ones shown here, the VLT Auxiliary Telescopes. This image shows three of the four moveable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: they reveal details that would be visible with a telescope as large as the distance between them.

30 December 2013

Bright Night at Paranal

When night falls, ESO's observatories spring to life. Astronomers and technicians take their positions, and telescopes are pointed skywards. This image shows the pristine skies over ESO's Paranal Observatory in the Chilean Atacama Desert, far away from city lights.

Here, ESO photo ambassador Gabriel Brammer has captured the serene beauty of the Milky Way from the platform of the Very Large Telescope. The four massive blocks in the bottom of the image are the four VLT Unit Telescopes, each of them housing incredibly precise 8.2-metre mirrors. Scattered around are the VLT's Auxiliary Telescopes, easily identifiable due to their round, white domes. The bright spot to the left is the Moon, shining as brightly as if it were the Sun, and to the right, the shadow of the photographer can be seen, waving to the viewer with outstretched arms.

The entire night sky is visible due to Brammer's use of a fish-eye lens, creating this circular effect with the ground bordering the frame.

23 December 2013

Season's Greetings from the European Southern Observatory!

Season's Greetings on behalf of everyone at the European Southern Observatory! We wish you a jolly end of the year and a fruitful 2014!


16 December 2013

Star Trails over the VLT in Paranal

This image was taken by Babak A. Tafreshi, one of ESO’s Photo Ambassadors, at ESO’s Paranal Observatory. It shows three of the four Auxiliary Telescopes (ATs) of the Very Large Telescope Interferometer (VLTI). Above them, the long bright stripes are star trails, each one marking the apparent path of a single star across the dark night sky, due to the rotation of the Earth. This technique also enhances the natural colours of the stars, which gives an indication of their temperature, ranging from about 1000 degrees Celsius for the reddest stars to a few tens of thousands of degrees Celsius for the hottest, which appear blue. The sky in this remote and high location in Chile is extremely clear and there is no light pollution, offering us this amazing light show.

9 December 2013

Brand New Image of Nova Centauri 2013

Alpha and Beta Centauri, two of the brightest stars in the southern sky, now have a new companion — the naked eye Nova Centauri 2013.

This photo was taken by ESO Photo Ambassador Yuri Beletsky at ESO's La Silla Observatory in the Chilean Atacama Desert in the morning hours of Monday 9 December 2013.

The nova was discovered by John Seach from Australia on 2 December 2013 as it approached naked eye brightness. Nova Centaurus 2013 is the brightest nova to have occurred so far this millennium.

This particular event is known as a classical nova, and is not to be confused with a supernova. Classical novae occur in binary star systems when hydrogen gas from the orbiting stellar partner is accreted onto the surface of the main star, causing a runaway thermonuclear event resulting in the brightening of the main star. In a classical novae the main star is not destroyed as is the case in a supernova. Instead, the star is dramatically brightened, and there is a simultaneous expansion of a debris shell.

The nova appears in the picture just to the left of Beta Centauri, the bluer and higher of the two bright stars in the lower-right part of the image. The Southern Cross and the Coal Sack Nebula are also captured near the top of the picture.

In front at the left is the ESO 3.6-metre telescope, inaugurated in 1976, it currently operates with the HARPS spectrograph, the most prolific exoplanet hunting machine in the world. Located 600 km north of Santiago, at 2400 m altitude in the outskirts of the Chilean Atacama Desert, La Silla was first ESO site in Chile and the largest observatory of its time.


2 December 2013

Zodiacal Glow Lightens Paranal Sky

This impressive photograph, taken at the site of ESO’s Very Large Telescope (VLT) at Paranal Observatory in Chile, shows, towards the centre left, the Milky Way — with its share of nebulae, stars, and gas clouds — rising above the VLT Unit Telescopes.

To the right, competing for attention as it arcs above the horizon, a beautiful, almost triangular band of diffuse light lies along the ecliptic, which is the apparent path of the Sun in the sky as seen from the Earth.

This glow originates in the scattering of sunlight by dust located between the planets that are spread through the plane of the Solar System. This coincides in the sky with the band known as the Zodiac, which extends for eight degrees of arc on either side of the ecliptic and contains the traditional zodiacal constellations.

25 November 2013

Ancient Constellations over ALMA

Babak Tafreshi, one of the ESO Photo Ambassadors, has captured the antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) in an enthralling image combining the beauty of the southern sky with the amazing dimensions of the biggest astronomical project in the world.

Thousands of stars are revealed to the naked eye in the clear skies over the Chajnantor Plateau. Its dry and transparent night sky is one of the reasons ALMA has been built here. Surprisingly bright in the upper left corner of the picture, there is a tightly packed bunch of young stars, the Pleiades Cluster, which was already known to most ancient civilisations. The constellation of Orion (The Hunter) is clearly visible over the closest of the antennas — the hunter’s belt is formed by the three blue stars just to the left of the red light. According to classic mythology, Orion was a hunter who chased the Pleiades, the beautiful daughters of Atlas. When seen through the thin atmosphere over the Atacama, it almost seems that this epic hunt is really happening.

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.

18 November 2013

New Image of Comet ISON

This new view of Comet C/2012 S1 (ISON) was taken with the TRAPPIST national telescope at ESO's La Silla Observatory on the morning of Friday 15 November 2013. Comet ISON was first spotted in our skies in September 2012, and will make its closest approach to the Sun in late November 2013.

TRAPPIST has been monitoring comet ISON since mid-October, using broad-band filters like those used in this image. It has also been using special narrow-band filters which isolate the emission of various gases, allowing astronomers to count how many molecules of each type are released by the comet.

Comet ISON was fairly quiet until 1 November 2013, when a first outburst doubled the amount of gas emitted by the comet. On 13 November, just before this image was taken, a second giant outburst shook the comet, increasing its activity by a factor of ten. It is now bright enough to be seen with a good pair of binoculars from a dark site, in the morning skies towards the East. Over the past couple of nights, the comet has stabilised at its new level of activity.

These outbursts were caused by the intense heat of the Sun reaching ice in the tiny nucleus of the comet as it zooms toward the Sun, causing the ice to sublimate and throwing large amounts of dust and gas into space. By the time ISON makes its closest approach to the Sun on 28 November (at only 1.2 million kilometres from its surface — just a little less than the diameter of the Sun!), the heat will cause even more ice to sublimate. However, it could also break the whole nucleus down into small fragments, which would completely evaporate by the time the comet moves away from the Sun's intense heat. If ISON survives its passage near the Sun, it could then become spectacularly bright in the morning sky.

The image is a composite of four different 30-second exposures through blue, green, red, and near-infrared filters. As the comet moved in front of the background stars, these appear as multiple coloured dots.

TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) is devoted to the study of planetary systems through two approaches: the detection and characterisation of planets located outside the Solar System (exoplanets), and the study of comets orbiting around the Sun. The 60-cm national telescope is operated from a control room in Liège, Belgium, 12 000 km away.


11 November 2013

ALMA Panoramic View with Carina Nebula

ESO Photo Ambassador, Babak Tafreshi captured this panoramic view of the antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) under the clear sky over the Chajnantor Plateau, in the Chilean Andes.

The rosy patch prominent at the left of the image is the Carina Nebula. It lies in the constellation of Carina (The Keel), about 7500 light-years from Earth. This cloud of glowing gas and dust is the one of brightest nebulae in the sky and contains several of the brightest and most massive stars known in the Milky Way, such as Eta Carinae. For some beautiful recent images of the Carina Nebula from ESO, see eso1208, eso1145, and eso1031.

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.

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