Picture of the Week 2011

21 March 2011

Supermoon over ESO's Very Large Telescope

The night of 19 March saw an unusual coincidence of astronomical events: the full Moon occurred at almost exactly the same time as the Moon was closest to Earth in its elliptical orbit (the point called perigee). The combination of the Moon being both full and relatively close to the Earth made it look significantly bigger and brighter than usual. This panoramic photograph, taken by ESO Photo Ambassador Gerd Hüdepohl, captures this so-called "supermoon" as seen from Cerro Paranal, home of ESO's Very Large Telescope (VLT).

On the right, in the east, the Moon rises over the mountains, while the setting Sun is visible on the left of the panorama, sinking in the west below the clouds over the Pacific Ocean. Its last rays illuminate the four giant VLT Unit Telescope buildings, the smaller VLT Survey Telescope building, the four round VLT Auxiliary Telescope enclosures, and the Paranal staff who have stepped out onto the mountaintop to watch the sunset and the moonrise.

The coincidence of a full Moon and perigee was a treat for observers. The Moon was about 30 000 km closer to us than average. So, the Moon looked about 14% bigger and 30% brighter than when at its most distant. Contrary to various reports, these "supermoons" have no significant effect on earthquakes or volcanoes, and there is no increased risk of natural disasters.

Although its closest approach to Earth in almost two decades gave observers a great photo opportunity, the Moon was still about 357 000 km away and remained far out of reach, even if one were standing on the 2600-metre mountaintop of Paranal. Luckily, we also have advanced astronomical telescopes such as the VLT, whose superb vision seems to bring even more distant astronomical objects within our grasp!

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14 March 2011

ALMA Antennas Reach Double Digits at Chajnantor

The number of antennas for the Atacama Large Millimeter/submillimeter Array (ALMA) on the Chajnantor plateau has now reached double digits! The tenth antenna was moved up from the Operations Support Facility at an altitude of 2900 metres to the Array Operations Site at 5000 metres, high in the Chilean Andes, on 4 March 2011 using one of the ALMA transporter vehicles.

ALMA is a telescope designed to observe millimetre- and submillimetre-wavelength light with its array of antenna dishes. Using a technique called interferometry, ALMA acts like a single giant telescope as large as the whole set of antennas. Thanks to the transporter vehicles, the antennas can be arranged in different configurations, where the maximum separation between them varies from 150 metres to 16 kilometres.

The distant viewpoint of this photograph is necessary for one to see all ten of the antennas in a single shot. Nine of them, including the newest addition, are clustered together on the left of the image, but the tenth is about 600 metres away on the right. ALMA is currently in a testing phase, and this lone antenna allows the astronomers and engineers to test the system’s performance with a longer baseline — the separation between a pair of antennas. When ALMA construction is completed in 2013, there will be a total of 66 antennas in the array.

The rare cloudy sky seen in the photograph is due to the Altiplanic Winter, in which the jet stream reverses and brings moist air from the east to this usually extremely arid site.

The ALMA project is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ESO is the European partner in ALMA.

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7 March 2011

A Quartet of ALMA Antennas Placed Close Together

The Atacama Large Millimeter/submillimeter Array (ALMA) antennas may look rooted to the ground in this striking image — taken at the Array Operations Site on the Chajnantor plateau, at an altitude of 5000 metres — but these dishes are surprisingly mobile.

Thanks to the two antenna transporter vehicles, the antennas in the array — which will consist of a total of 66 dishes when construction is complete — can be repositioned to meet the needs of a particular observation project. The transporters, named Otto and Lore, were specially designed to transport the hefty 115-tonne antennas and position them precisely on concrete foundation pads, spread across the plateau over distances of up to 16 kilometres. Here, four antennas have been placed on closely spaced pads for testing during the Commissioning and Science Verification phase of ALMA construction.

The transporter vehicles drive on 28 tyres, with two 700-HP (500 kW) diesel engines and two 1500-litre fuel tanks, and have a top speed of 12km/h when carrying their precious cargo.

The ALMA project is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ESO is the European partner in ALMA.


28 February 2011

ALMA Antennas Stand Together

ALMA antennas stand side by side, built strong to withstand the unforgiving environment of the Chajnantor plateau, high in the Chilean Andes. At an altitude of 5000 m, the ALMA dishes — a total of 66 when construction is completed — will face strong winds and harsh sunlight, all without the safe haven of a protective dome. The temperature can vary by 40 degrees Celsius, dipping well below freezing and occasionally allowing snow to fall, as can be seen dusting the landscape in the background of this photograph.

The ALMA project is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ESO is the European partner in ALMA.

This photograph was taken by ESO Photo Ambassador José Francisco Salgado.

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21 February 2011

ALMA antennas under the Milky Way

Four antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) gaze up at the star-filled night sky, in anticipation of the work that lies ahead. The Moon lights the scene on the right, while the band of the Milky Way stretches across the upper left.

ALMA is being constructed at an altitude of 5000 m on the Chajnantor plateau in the Atacama Desert in Chile. This is one of the driest places on Earth and this dryness, combined with the thin atmosphere at high altitude, offers superb conditions for observing the Universe at millimetre and submillimetre wavelengths. At these long wavelengths, astronomers can probe, for example, molecular clouds, which are dense regions of gas and dust where new stars are born when a cloud collapses under its own gravity. Currently, the Universe remains relatively unexplored at submillimetre wavelengths, so astronomers expect to uncover many new secrets about star formation, as well as the origins of galaxies and planets, when ALMA is operational.

The ALMA project is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile.

This picture was taken by ESO Photo Ambassador José Francisco Salgado.

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14 February 2011

A Galactic Petri Dish

This rich scattering of galaxies was captured using the Wide Field Imager attached to the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. The thousands of galaxies contained in this small area of sky give a glimpse into the Universe’s distant past, whilst also acting as a powerful reminder of the immense scale of the cosmos.

This image was taken as part of the COMBO-17 project (Classifying Objects by Medium-Band Observations in 17 Filters), in which detailed surveys of five small patches of sky were made through 17 different coloured filters. The area of sky covered by each of the five regions is about the same area as that covered by the full Moon. The survey has produced a remarkable haul of celestial specimens. For example, across just three of these regions over 25 000 galaxies have been identified.

Just below the bright stars in the centre of the image is the galaxy cluster Abell 226. It was first noted by astronomer George Ogden Abell in his catalogue of galaxy clusters of 1958. The galaxies in Abell’s clusters, including Abell 226, are only up to a few billion light-years away. But behind these objects, even fainter, more distant galaxies were hiding.

The COMBO-17 study has unveiled these hidden galaxies, thanks to long exposure images from the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. Some of the most distant flecks of light visible in this photo represent galaxies whose light has been travelling towards us for about nine or ten billion years. That means that the galaxies in this image have a great variety of ages, some of them are quite similar to the Milky Way, while others reveal what the Universe was like when it was much younger.

This image was taken using three of the 17 filters from the study: B (in blue), V (in green), and R (in red).

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7 February 2011

HAWK-I Instrument Spies a Super Galaxy

The HAWK-I instrument on ESO's Very Large Telescope (VLT) at the Paranal Observatory in Chile has been used to great effect in producing this distinctive image of the distant galaxy NGC 157. Boasting a central sweep of stars resembling a giant "S", reminiscent of the comic book hero Superman’s symbol, this celestial spiral is indeed a super example of how new technology is helping us to learn more about the cosmos.

HAWK-I stands for High-Acuity Wide-field K-band Imager, and it is one of the latest and most powerful instruments on the VLT. It detects infrared light, allowing us to peer through the gas and dust that normally obscures our view. This reveals an otherwise hidden view of the Universe, and gives astronomers the opportunity to study dense areas of star formation.

Learning more about star formation is an important step towards expanding our understanding of our own origins. The same processes that are coalescing material in NGC 157 and creating stars there took place around 4.5 billion years ago in the Milky Way to form our own star, the Sun.

NGC 157 is faint at about magnitude 11, but can be tracked down by dedicated amateur astronomers. It is located within the constellation of Cetus (the Sea Monster).


31 January 2011

From One "Alien World" to Another

What looks like a barren and inhospitable alien landscape in this 360-degree panorama is in fact the site for ESO’s European Extremely Large Telescope, or E-ELT for short. When construction begins the uninhabited mountaintop left of the centre will become a hive of activity as engineers, technicians and scientists work on building the world’s biggest eye on the sky.

In many ways Chile’s Cerro Armazones may seem like an alien world. The environment is harsh, with low humidity and air pressure, a blazing Sun during the day, but breathtaking skies at night. Cerro Armazones is in the Atacama Desert — one of the driest places on Earth. These conditions, combined with its remoteness, are what make the region such an excellent location for telescopes. Armazones is an isolated peak, 3060 metres above sea level. It is about 20 km away from Cerro Paranal, home of ESO's famous Very Large Telescope. Both summits enjoy crisp skies far away from sources of light pollution.

Among the ELT’s many science goals is a particularly hot topic in contemporary astronomy: the quest for exoplanets. The E-ELT will search for Earth-like planets orbiting other stars and could even directly image larger planets or probe their atmospheres. The E-ELT’s high-tech instruments will also study the formation of planets in protoplanetary discs around young stars. Detecting water and organic molecules will shed light on how planetary systems are produced, and could bring us one step closer to answering the question of whether we are alone in the Universe.

This panorama was taken by ESO Photo Ambassador Serge Brunier.

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24 January 2011

A New Era for Astronomy

As the Sun sets over Cerro Armazones, plans are well advanced for building the world's biggest “eye on the sky”: ESO's European Extremely Large Telescope (E-ELT). With a primary mirror 39 metres in diameter, the E-ELT will dwarf all existing visible-light telescopes.

Site selection has been a vital part of the plans for the E-ELT. Over the course of several years a team of experts investigated locations around the world, looking for the best place to host such an ambitious project. The site for the E-ELT must be remote enough not to be influenced by problems such as light pollution, but also needs the necessary infrastructure for the construction and operation of the observatory, and to accommodate the over 150 staff who will eventually work there. Monitoring stations, such as the one shown here, were set up to test site conditions scientifically by measuring parameters that included atmospheric turbulence and levels of water vapour. By better understanding the atmosphere at a site, the team were able to determine the best potential site for the highest quality science.

The list of potential sites included areas in Argentina, in Chile, in Morocco and in Spain. Cerro Armazones in Chile, shown in this photograph, was finally selected as the E-ELT site because it has the best balance of sky quality across all aspects and it can be operated in an integrated fashion with the existing ESO Paranal Observatory nearby. Armazones is about 20 km from Paranal and 130 km south of the nearest town. It is 3060 metres above sea level and boasts almost 350 cloudless nights a year.

Constructing the E-ELT is a huge undertaking that will take several years. The go-ahead for construction is planned for 2011, with start of operations planned for early in the next decade. When observations begin, the E-ELT will herald a new era for astronomy.


17 January 2011

Sailing the Atacama Desert

Like the bow of a ship sailing a rolling ocean of red hills, the southeast corner of the observing platform at Paranal stands over the Mars-like landscape of the Chilean Atacama Desert. This panorama shows the breathtaking view of the horizon, and conveys the feeling of immensity experienced when looking from the top of Cerro Paranal, a remote 2600-metre-high mountain located in one of the driest regions on Earth.

Atop Cerro Paranal is the ESO Very Large Telescope (VLT), the world’s most advanced optical and near infrared ground-based astronomical facility, composed of four 8.2-metre Unit Telescopes (UTs) and four 1.8-metre Auxiliary Telescopes (ATs). The fourth Unit Telescope (UT4), named Yepun in the Mapuche language, is most prominent in this photograph, while UT3 (Melipal) and UT1 (Antu) are just visible on the right-hand edge of the picture. Three of the smaller ATs can also be seen on the 200-metre-wide observing platform. The yellow structure in front of Yepun is the “M1 Lifting Platform”, used to move the 8.2-metre-diameter primary mirror (M1) and its support structure out of the telescope building for periodic recoating.

In the distance, over the edge of the platform, is the Paranal Observatory base camp, which includes the Residencia, the Main Maintenance Building, the power station and the warehouse. These facilities are situated some 2 km away from the telescopes, at a lower altitude of about 2400 metres. The whole observatory complex operates as an “island” in the desert, where essentials such as water, food and fuel must be brought from Antofagasta, located about 120 km to the north. The remoteness of the site makes operating Paranal Observatory a great logistical challenge, but the reward is a location with superb conditions for astronomy.


10 January 2011

The VLT “Venus” and the Belt of Venus

Before another clear, starry night falls at ESO's Paranal Observatory, home of the Very Large Telescope (VLT), the sky produces a palette of intense colours, putting on a beautiful show for observers. These colours can only be seen with such depth from sites such as Paranal, where the atmosphere is extraordinarily pure. Looking to the west, over the Pacific Ocean, the sunset sky turns bright orange and red. However, this photograph shows the view to the east instead, looking away from the Sun after it has just set. The grey-bluish shadow above the horizon is the shadow of our own planet. Above this is a pinkish glow known as the "Belt of Venus", a phenomenon produced by the reddened light of the setting Sun being backscattered by the Earth's atmosphere.

In the centre of the image is the fourth 8.2-metre Unit Telescope (UT4), part of the VLT. The Mapuche name given to UT4 is Yepun, which means Venus. As well as working as individual telescopes, groups of two or three UTs can combine their light using a technique called interferometry, which allows astronomers to see details up to 25 times finer than with the individual telescopes. The VLT also has four 1.8-metre Auxiliary Telescopes (ATs), housed in ultra-compact mobile enclosures, which are fully dedicated to interferometric observations. Two of the ATs are visible in the background, with a third mostly hidden.

The yellow frame-like structure in front of Yepun is the "M1 Lifting Platform", used when the giant 8.2-metre primary mirror (M1) of the telescope is periodically recoated. The delicate mirror and its support structure, which together weigh 45 tonnes, are removed from the telescope enclosure and slowly driven about two kilometres to a maintenance building at the Paranal base camp. This process is, unsurprisingly, performed with the utmost care.

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3 January 2011

Another Perfect Day at Paranal

Rolling red hills stretch out below the exceptionally clear blue sky that is typical of ESO's Paranal Observatory. Although the telescope domes close at dawn, and nothing seems to move on the surface of this barren desert, the ESO Very Large Telescope (VLT) never rests. Since early morning, a team of engineers and technicians has been working hard to prepare the telescopes and instruments for another "perfect night".

The 2600-metre-high Cerro Paranal stands out at the centre of this panoramic view, taken looking towards the south. This flattened mountaintop is home to the VLT, the world's most advanced ground-based optical and near infrared astronomical facility. The VLT has four 8.2-metre Unit Telescopes (UTs), plus four 1.8-metre Auxiliary Telescopes (ATs). In this picture, only two of the UT enclosures, together with the smaller 2.6-metre VLT Survey Telescope (VST) are visible.

To the right of Cerro Paranal, the sea of clouds that typically covers the coast of the Pacific Ocean — only 12 km away — is visible in the background. The cold oceanic stream typically keeps the thermal inversion layer of the atmosphere below an altitude of 1500 metres, making this remote area of the Chilean Atacama Desert in the II Region of Chile one of the driest sites on Earth and a perfect window on the Universe. The atmosphere here is extremely dry and clear, and has very low turbulence, offering the most suitable conditions for optical and near-infrared astronomical observations.

For this reason, the 3060-metre-high Cerro Armazones, located just some 20 km east of Paranal, was selected as the site for the future European Extremely Large Telescope (E-ELT). With a primary mirror 39 metres in diameter, the E-ELT will be the world's largest eye on the sky.

This photograph was taken from a neighbouring mountain, home of the 4.1-metre Visible and Infrared Survey Telescope for Astronomy (VISTA). VISTA started operations at the end of 2009 and is the most recent telescope to be added to the roster at ESO's Paranal Observatory. VISTA is the largest survey telescope in the world.

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