Picture of the Week

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potw1148 — Picture of the Week
A Galaxy Full of Surprises — NGC 3621 is bulgeless but has three central black holes
28 November 2011: This image, from ESO’s Very Large Telescope (VLT), shows a truly remarkable galaxy known as NGC 3621. To begin with, it is a pure-disc galaxy. Like other spirals, it has a flat disc permeated by dark lanes of material and with prominent spiral arms where young stars are forming in clusters (the blue dots seen in the image). But while most spiral galaxies have a central bulge — a large group of old stars packed in a compact, spheroidal region — NGC 3621 doesn’t. In this image, it is clear that there is simply a brightening to the centre, but no actual bulge like the one in NGC 6744 (eso1118), for example. NGC 3621 is also interesting as it is believed to have an active supermassive black hole at its centre that is engulfing matter and producing radiation. This is somewhat unusual because most of these so-called active galactic nuclei ...
potw1147 — Picture of the Week
A Double Green Flash
21 November 2011: At sunset, the sky is often painted with an array of oranges, reds and yellows, and even some shades of pink. There are, however, occasions when a green flash appears above the solar disc for a second or so. One such occurrence was captured beautifully in this picture taken from Cerro Paranal, a 2600-metre-high mountain in the Chilean Atacama Desert, by ESO Photo Ambassador Gianluca Lombardi. Cerro Paranal is home to ESO’s Very Large Telescope. The green flash is a rather rare phenomenon; seeing such a transient event requires an unobstructed view of the setting (or rising) Sun and a very stable atmosphere. At Paranal the atmospheric conditions are just right for this, making the green flash a relatively common sight (see for example eso0812). But a double green flash such as this one is noteworthy even for Paranal. The green flash occurs because the Earth’s atmosphere works like a ...
potw1146 — Picture of the Week
Working at ALMA, Day and Night
14 November 2011: In the foothills of the Chilean Andes, at an altitude of 2900 metres, the Operations Support Facility (OSF) for the Atacama Large Millimeter/submillimeter Array (ALMA) is a hive of activity. This photograph shows engineers moving a heavyweight antenna at night — with the help of a special 28-wheel transporter — and illustrates how work at ALMA continues around the clock. The antenna, one of 25 provided for the ALMA project by ESO, is being moved into position next to antennas from the other ALMA partners to be tested and equipped with highly sensitive detectors. When completed, ALMA will consist of 66 12-metre and 7-metre antennas that will work together as a giant radio telescope observing at millimetre and submillimetre wavelengths. The facility will allow astronomers to study our cosmic origins by probing the first stars and galaxies, and imaging the formation of planets. The telescope is being constructed on Llano ...
potw1145 — Picture of the Week
GRAAL on a Quest to Improve HAWK-I's Vision
7 November 2011: This image shows some of the GRAAL instrument team, inspecting GRAAL’s mechanical assembly in the integration hall of ESO’s Headquarters in Garching bei Munchen, Germany. GRAAL, which will be installed on ESO’s Very Large Telescope (VLT) on Cerro Paranal in Chile, is designed to improve the vision of the VLT’s already excellent HAWK-I camera even further. GRAAL stands for GRound layer Adaptive optics Assisted by Lasers. It will use the technique of adaptive optics to improve the quality of images by compensating for turbulence in the lower layers of the atmosphere, up to an altitude of 1 kilometre. GRAAL will form part of the observatory’s next generation Adaptive Optics Facility (AOF). The VLT already uses a powerful laser beam to create an artificial guide star, 90 kilometres up in the atmosphere. The current adaptive optics systems use this guide star as a reference to remove the effect of turbulence in the ...
potw1144 — Picture of the Week
Twinkle Twinkle Little Star
31 October 2011: A glowing laser shines forth from the European Southern Observatory’s Very Large Telescope. Piercing the dark Chilean skies, its mission is to help astronomers explore the far reaches of the cosmos. ESO Photo Ambassador Gerhard Hüdepohl was on hand to capture the moment in a stunning portrait of modern science in action.  We have all gazed up at the night sky and seen the stars gently twinkle as the Earth’s turbulent atmosphere causes their light to shimmer. This is undoubtedly a beautiful sight, but it causes problems for astronomers, who want the crispest possible views. To help them achieve this, professional stargazers use something that sounds as though it has come from science fiction: a laser guide star that creates an artificial star 90 km above the surface of the Earth. The method by which it achieves this is nothing short of remarkable. The laser energises sodium atoms high in ...
potw1143 — Picture of the Week
Portrait of an Imperfect but Beautiful Spiral
24 October 2011: Not all spiral galaxies have to be picture-perfect to be striking. Messier 96, also known as NGC 3368, is a case in point: its core is displaced from the centre, its gas and dust are distributed asymmetrically and its spiral arms are ill-defined. But this portrait, taken with the FORS1 instrument on ESO’s Very Large Telescope, shows that imperfection is beauty in Messier 96. The galaxy's core is compact but glowing, and the dark dust lanes around it move in a delicate swirl towards the nucleus. And the spiral arms, patchy rings of young blue stars, are like necklaces of blue pearls.   Messier 96 lies in the constellation of Leo (The Lion). It is the largest galaxy in the Leo I group of galaxies; including its outermost spiral arms, it spans some 100 000 light-years in diameter — about the size of our Milky Way. Its graceful imperfections likely ...
potw1142 — Picture of the Week
Stars Dancing Above the VLT
17 October 2011: The night sky above the 2600-metre-high Cerro Paranal in the Atacama Desert in Chile is dark and clear. So clear, that very long sequences of photos can easily be taken without a single cloud obscuring the stars as they rotate around the southern celestial pole. The site is home to ESO’s Very Large Telescope (VLT) array. Its four 8.2-metre Unit Telescopes dominate this image made by Farid Char, a student at Chile’s Universidad Católica del Norte. One of the smaller Auxiliary Telescopes is also visible, hiding in the background in the bottom left corner. But the star of the show is the striking starry sky. Made by combining 450 exposures of 20 seconds each, the image captures the apparent stellar movement during two and a half hours. This movement, signalled by dotted trails, is illusory: the Earth, and not the stars, is rotating as time goes by. The sequence has ...
potw1141 — Picture of the Week
Flying above the ALMA Site: The Operations Support Facility
10 October 2011: This spectacular aerial view shows the ALMA Operations Support Facility (OSF), located 2900 metres above sea level in the foothills of the Chilean Andes, near San Pedro de Atacama. ALMA, the Atacama Large Millimeter/submillimeter Array, is currently under construction on the 5000-metre-high Chajnantor plateau. Such a high altitude site is necessary for ALMA’s array of antennas to observe the Universe in millimetre and submillimetre radiation, but the lack of oxygen makes the Array Operations Site (AOS) a very uncomfortable place for people to work. For this reason, as much of the scientific and technical work as possible takes place at the OSF, which is 2100 metres lower in altitude. The antennas are even controlled remotely from the OSF. In this picture, from the bottom left to the centre right, the North American, the Japanese and the European antenna assembly facilities are clearly distinguishable. In these areas, the antennas are assembled ...
potw1140 — Picture of the Week
VLT Observes the Antennae Galaxies
3 October 2011: A new Very Large Telescope (VLT) image of the Antennae Galaxies gives us what may be the second-best visible-light view yet of this striking pair of colliding galaxies with dramatically distorted shapes. This amazing object takes its name from the long antenna-like "arms" extending far out from the nuclei of the two galaxies, best seen in wider-field images by ground-based telescopes such as the one at this link. This VLT view focuses instead on the galaxies’ nuclei, where the real action is taking place as the two galaxies merge into a single giant galaxy. Spurred by shock waves created by their gravitational wrestling, the two galaxies have become dotted with brilliant blue hot young stars in star-forming regions, surrounded by glowing hydrogen gas, shown here in pink. The two pale yellow blobs are the cores of the original galaxies, shining with the light of old stars and picked out by ...
potw1139 — Picture of the Week
All Four VLT Unit Telescopes Working as One
26 September 2011: When light from all four 8.2-metre Unit Telescopes of ESO’s Very Large Telescope (VLT) in Cerro Paranal on 17 March 2011 was successfully combined for the first time (ann11021), ESO Photo Ambassador Gerhard Hüdepohl was there to capture the moment. Having all four of the Unit Telescopes (UTs) working as one telescope observing the same object was a major step in the development of the VLT. While mostly used for individual observations, the UTs were always designed to be able to operate together as part of the VLT Interferometer (VLTI). All the UTs are pointed in the same direction, at the same object, although this isn’t obvious because of the wide-angle lens used to take the photo. The light collected by each of the telescopes was then combined using an instrument called PIONIER [1]. When combined, the UTs can potentially provide an image sharpness that equals that of a telescope ...
potw1138 — Picture of the Week
The “Little World” of Paranal
19 September 2011: This interpretation of a previous Picture of the Week was created by astronomer Alex Parker. It captures some of the essence of Paranal Observatory — a little world where astronomers leave the Earth behind and travel to the stars... metaphorically at least. The observatory lies deep in the barren Atacama Desert, which can really seem like an alien environment. It is far from civilisation and modern life, a place where visiting astronomers spend their nights gazing out at the wonders of the Universe using ESO’s flagship facility, the Very Large Telescope (VLT). The VLT is the reason why Cerro Paranal was transformed from just another mountain in the Chilean Andes into a base for world-class scientific research. When night falls over Paranal, and the night sky is aglow with stars, nebulae and nearby galaxies, the unearthly view emphasises our place in the Universe — as Alex Parker so creatively demonstrates ...
potw1137 — Picture of the Week
Red Moon Rising
12 September 2011: Deep in the heart of the Atacama Desert, home of the Paranal Observatory, the Sun is setting at the start of another clear night. This charming photograph, taken by ESO Photo Ambassador Gianluca Lombardi shows one of four Auxiliary Telescopes (ATs) that belong to ESO’s Very Large Telescope (VLT) sitting boldly against a vivid sky of pink and blue. The full Moon, seen hovering over the horizon, has a distinctly reddish hue, a phenomenon caused by the scattering of light by Earth’s atmosphere. When the Moon is close to the horizon, the light we see from it must travel through a greater thickness of the atmosphere, so the effects of scattering are increased. As red light is more resilient to scattering than green or blue, our view of the Moon is reddened. As it happens, the reddening effect is somewhat less pronounced at sites like Paranal, as the clear air ...
potw1136 — Picture of the Week
Laser Meets Lightning
5 September 2011: As ESO tested the new Wendelstein laser guide star unit by shooting a powerful laser beam into the atmosphere, one of the region’s intense summer thunderstorms was approaching — a very visual demonstration of why ESO’s telescopes are in Chile, and not in Germany. Heavy grey clouds threw down bolts of lightning as Martin Kornmesser, visual artist for the ESO outreach department, took time-lapse photographs of the test for ESOcast 34. With purely coincidental timing this photograph was snapped just as lightning flashed, resulting in a breathtaking image that looks like a scene from a science fiction movie. Although the storm was still far from the observatory, the lightning appears to clash with the laser beam in the sky. Laser guide stars are artificial stars created 90 kilometres up in the Earth’s atmosphere using a laser beam. Measurements of this artificial star can be used to correct for the blurring ...
potw1135 — Picture of the Week
First 7-metre ALMA Antenna Arrives at Chajnantor
29 August 2011: The first of twelve 7-metre diameter ALMA antennas has just been transported on 24 August 2011 to the 5000-metre-high Chajnantor plateau, where the Atacama Large Millimeter/submillimeter Array (ALMA) is under construction. ALMA is a giant radio telescope composed of an array of fifty 12-metre antennas, as well as a smaller array known as the Atacama Compact Array (ACA). This will have a total of four 12-metre antennas and the twelve 7-metre dishes. The four 12-metre ACA antennas have already been moved up to the high plateau, but this is the first of the smaller 7-metre dishes — which put the “compact” into Atacama Compact Array — to reach Chajnantor. It is seen in the centre of this photograph, surrounded by some of the other ALMA antennas. Penitentes ice formations are seen in the foreground.The larger 12-metre antennas of the main array cannot be placed closer than 15 metres apart as ...
potw1134 — Picture of the Week
Flying over the ALMA Site: The Array Operations Site
22 August 2011: ALMA, the Atacama Large Millimeter/submillimeter Array, will be initially composed of 66 antennas, designed to observe the Universe in millimetre and submillimetre radiation. The main array will consist of fifty 12-metre antennas that can be spread over distances from 150 metres to 16 kilometres. In addition to the main array, ALMA will also have a compact array, composed of four 12-metre antennas plus twelve 7-metre antennas. By using the technique of interferometry, ALMA will work as a single giant telescope, enabling astronomers to observe the cold universe with unprecedented sensitivity and resolution. From the high altitudes of the Andes, ALMA will provide a revolutionary contribution to the search for our cosmic origins. 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 ...
potw1133 — Picture of the Week
As Time Goes By
15 August 2011: Just as the Sun rises in the east and sets in the west, so do the stars appear to slowly march across the sky. Their leisurely pace is imperceptible to a casual observer, but you can test the effect for yourself: on the next clear night note the position of a bright star, and then check again a few hours later. The change is not caused by the motion of the stars themselves, but rather the rotation of the Earth. Long-exposure photography is the ideal way to capture this motion. A camera is set up on a tripod, and the shutter opened to the sky. Normal snapshots gather light for a fraction of a second, but these special images need starlight to pour onto them for much longer, like a bucket collecting rainwater. To obtain this image, ESO Photo Ambassador Gianluca Lombardi collected light for a total of 25 minutes. ...
potw1132 — Picture of the Week
Dark Sky and White Desert — Snow pays a rare visit to ESO’s Paranal Observatory
8 August 2011: The night sky above Cerro Paranal, the home of ESO’s Very Large Telescope (VLT), is dark and dotted with the bright stars of the Milky Way, and more distant galaxies. But it is very rare to see the ground contrasting with the sky as markedly as in this photograph, which shows a gentle layer of white snow dotted with darker spots of the desert terrain beneath. The picture was taken last week, shortly before sunrise, by ESO Photo Ambassador Yuri Beletsky, who works as an astronomer at the La Silla Paranal Observatory. He captured not only the beautiful snowy landscape of the Atacama and the mountaintop domes of the VLT, but also an incredible night sky. To the left of the VLT is a satellite trail, and to the right is the trail of a meteor.Cerro Paranal is a 2600-metre-high mountain located in the Chilean Atacama Desert. It is a ...
potw1131 — Picture of the Week
Smoke Signals in Space
1 August 2011: The hazy and aptly named Fine Ring Nebula, shown here, is an unusual planetary nebula. Planetary nebulae form when some dying stars, having expanded into a red giant phase, expel a shell of gas as they evolve into white dwarfs. Most planetary nebulae are either spherical or elliptical in shape, or bipolar (featuring two symmetric lobes of material). But the Fine Ring Nebula — captured here by the ESO Faint Object Spectrograph and Camera mounted on the New Technology Telescope at the La Silla Observatory in Chile — looks like an almost perfect circular ring. Astronomers believe that some of these more unusually shaped planetary nebulae are formed when the progenitor star is actually a binary system. The interaction between the primary star and its orbiting companion shapes the ejected material. The stellar object at the centre of the Fine Ring Nebula is indeed thought to be a binary system, ...
potw1130 — Picture of the Week
Very Large Telescope Ready for Action
25 July 2011: This unusual 360-degree panoramic projection reveals the observing site from a fresh perspective. In the centre of the image, staff at Paranal have gathered to watch the sunset. On the right, the enclosures of the VLT’s Unit Telescopes can be seen: vast machines, each with a primary mirror 8.2 metres across and weighing 23 tonnes. Also visible are several of the smaller 1.8-metre Auxiliary Telescopes, which complement the Unit Telescopes. On the left of the picture is the control building, from where the telescopes are operated remotely during observations. No one remains inside the telescope domes after they are opened. Since first light in 1998 the Very Large Telescope has been used by ESO astronomers to study the Universe, including some of the most exotic phenomena known, such as exoplanets, supermassive black holes, and gamma-ray bursts. An amazing interactive virtual tour of Paranal is available here.
potw1129 — Picture of the Week
Hidden Treasure on Our Doorstep
18 July 2011: The MPG/ESO 2.2-metre telescope at La Silla in Chile is a powerful instrument that can capture distant celestial objects, but it has been used here to image a heavenly body that is much closer to home: the Moon. The data used for this image were selected by Andy Strappazzon from Belgium, who participated in ESO’s Hidden Treasures 2010 astrophotography competition. Andy’s composition of the Moon was the fourth highest ranked entry in the competition. This image of the crescent Moon shows sunlight skimming across the heavily pocked surface, filling its craters with shadows. This is a fairly flat region of the Moon, but elsewhere, high mountains can be found, with some peaks reaching about 5000 metres. When backlit by the Sun, these mountains cast long shadows on the lunar surface. In the 1600s, Galileo Galilei used these long shadows to determine the height of the peaks. At the Moon’s poles ...
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