Picture of the Week 2013

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potw1312a — Picture of the Week
The Lost Galaxy
25 March 2013: This image depicts the galaxy NGC 4535, in the constellation of Virgo (The Maiden), on a beautiful background full of many distant faint galaxies. Its almost circular appearance shows that we observe it nearly face-on. In the centre of the galaxy, there is a well-defined bar structure, with dust lanes that curve sharply before the spiral arms break from the ends of the bar. The bluish colour of the spiral arms points to the presence of a large number of hot young stars. In the centre, however, older and cooler stars give the bulge of the galaxy a yellower appearance. This visible image was made with the FORS1 instrument on ESO’s 8.2-metre Very Large Telescope. The galaxy can also be seen through smaller amateur telescopes, and was first observed by William Herschel in 1785. When seen through a smaller telescope, NGC 4535 has a hazy, ghostly appearance, which inspired the ...
potw1311 — Picture of the Week
Catching Light
18 March 2013: Research telescopes sport state-of-the-art cameras which, together with the big mirrors needed for a large collecting area, allow astronomers to catch the faint light of deep sky objects. But you can also produce beautiful images without big telescopes and using more modest cameras. Astrophotographers use more conventional cameras to capture images of astronomical objects, often on a larger scale than the observations made with big telescopes. Sometimes, they include the landscape in their composition, producing beautiful postcards of the Universe as seen from Earth. For example, this Picture of the Week shows the 3.58-metre New Technology Telescope (NTT), located at ESO’s La Silla Observatory, and set against the starry background of the southern sky. Standing out in the image, the Milky Way — our home galaxy — can be seen as a hazy stripe across the sky. Dark regions within the Milky Way are areas where the light from background ...
potw1310 — Picture of the Week
Comets and Shooting Stars Dance Over Paranal
11 March 2013: This impressive picture was taken on 5 March 2013 by Gabriel Brammer, one of the ESO Photo Ambassadors, and shows a sunset view of the Paranal Observatory, featuring two comets that are currently moving across the southern skies. Close to the horizon, on the right-hand side of the image, Comet C/2011 L4 (Pan-STARRS), the brightest of the two, shows a bright tail that is caused mainly by dust reflecting the sunlight. In the centre of the image, just above the right-hand slopes of Cerro Paranal, the greenish coma — a nebulous envelope around the nucleus — of Comet C/2012 F6 (Lemmon) can be distinguished, followed by a fainter tail. The green colour is a result of the ionisation of gases in the coma by sunlight. You might even be tricked into thinking that there is a third comet visible in this photo, but the bright object whizzing between comets Lemmon and ...
potw1309 — Picture of the Week
Snow Comes to the Atacama Desert
4 March 2013: The Atacama Desert is one of the driest places in the world. Several factors contribute to its arid conditions. The magnificent Andes mountain range and the Chilean Coast Range block the clouds from the east and west, respectively. In addition, the cold offshore Humboldt Current in the Pacific Ocean, which creates a coastal inversion layer of cool air, hinders the formation of rain clouds. Moreover, a region of high pressure in the south-eastern Pacific Ocean creates circulating winds, forming an anticyclone, which also helps to keep the climate of the Atacama Desert dry. These arid conditions were a major factor for ESO in placing the Very Large Telescope (VLT) at Paranal, in the Atacama Desert. At the Paranal Observatory, located on the summit of Cerro Paranal, the precipitation levels are usually below ten millimetres per year, with the humidity often dropping below 10%. The observational conditions are excellent, with over ...
potw1308 — Picture of the Week
The Comet and the Laser
25 February 2013: Gerhard Hüdepohl, one of the ESO Photo Ambassadors, captured this spectacular image of ESO’s Very Large Telescope (VLT) during the testing of a new laser for the VLT 14 February 2013. It will be used as a vital part of the Laser Guide Star Facility (LGSF), which allows astronomers to correct for most of the disturbances caused by the constant movement of the atmosphere in order to create much sharper images. Nevertheless, is hard not to think of it as a futuristic laser cannon being pointed towards some kind of distant space invader. As well as the amazing view of the Milky Way seen over the telescope, there is another feature making this picture even more special. To the right of the centre of the image, just below the Small Magellanic Cloud and almost hidden among the myriad stars seen in the dark Chilean sky, there is a green dot with a faint tail ...
potw1307 — Picture of the Week
Super-thin Mirror Under Test at ESO
18 February 2013: This remarkable deformable thin-shell mirror has been delivered to ESO at Garching, Germany and is shown undergoing tests. It is 1120 millimetres across but just 2 millimetres thick, making it much thinner than most glass windows. The mirror is very thin so that it is flexible enough for magnetic forces applied to it to alter the shape of its reflective surface. When in use, the mirror's surface will be constantly changed by tiny amounts to correct for the blurring effects of the Earth’s atmosphere and so create much sharper images. The new deformable secondary mirror (DSM) will replace the current secondary in one of the VLT’s four Unit Telescopes. The entire secondary structure includes a set of 1170 actuators that apply a force on 1170 magnets glued to the back face of the thin shell. Sophisticated special-purpose electronics control the behaviour of the thin shell mirror. The reflecting surface can ...
potw1306 — Picture of the Week
Laser and Light Painting
11 February 2013: On a clear night in Bavaria, ESO staff attended the filming of an ESOcast episode focusing on ESO’s new compact laser guide star unit, seen here in action at the Allgäu Public Observatory in Ottobeuren, Germany. Using the glow from their mobile phones, staff took advantage of the long-exposure photograph to draw the letters “ESO” in light, while standing in front of the observatory. Just left of the vertical laser beam, the Milky Way can be seen. Just above the horizon over the observatory, the dotted tracks of aircraft can be seen in the distance. The laser has a powerful beam of 20 watts, and to protect pilots and passengers a no-fly zone around the observatory was created by the Deutsche Flugsicherung (responsible for air traffic control in Germany) during the nighttime observing hours. Laser guide stars are artificial stars created in the Earth’s atmosphere using a laser beam. The ...
potw1305 — Picture of the Week
Sunset at Paranal Observatory
4 February 2013: Babak Tafreshi, an ESO Photo Ambassador, has captured a beautiful image of ESO’s Paranal Observatory illuminated by the sunset. The beautifully clear sky hints at the exceptional atmospheric conditions here; one major reason why ESO chose Paranal as the site of the Very Large Telescope (VLT), its flagship facility.The VLT — which can be seen on Cerro Paranal, the highest peak in the image, with an altitude of 2600 metres —  is the world’s most advanced visible-light astronomical observatory. It consists of four Unit Telescopes, each with a primary mirror 8.2 metres across, and four 1.8-metre Auxiliary Telescope. The VLT operates at visible and infrared wavelengths and among the pioneering observations carried out using the VLT have been the first direct image of an exoplanet (see eso0515) and the tracking of stars orbiting the Milky Way’s central black hole (see eso0846 and eso1151). Also on Cerro Paranal is the VLT ...
potw1304 — Picture of the Week
An Intergalactic Heavyweight
28 January 2013: This deep-field image shows what is known as a supercluster of galaxies — a giant group of galaxy clusters which are themselves clustered together. This one, known as Abell 901/902, comprises three separate main clusters and a number of filaments of galaxies, typical of such super-structures. One cluster, Abell 901a, can be seen above and just to the right of the prominent red foreground star near the middle of the image. Another, Abell 901b, is further to the right of Abell 901a, and slightly lower. Finally, the cluster Abell 902 is directly below the red star, towards the bottom of the image. The Abell 901/902 supercluster is located a little over two billion light-years from Earth, and contains hundreds of galaxies in a region about 16 million light-years across. For comparison, the Local Group of galaxies — which contains our Milky Way among more than 50 others — measures roughly ...
potw1303 — Picture of the Week
APEX Under the Moon
21 January 2013: Another starry night on the Chajnantor Plateau in the Chilean Andes. The first quarter Moon glows brightly in this exposure, outshining the surrounding celestial objects. However, for radio telescopes such as APEX (the Atacama Pathfinder Experiment), seen here, the brightness of the Moon is not a problem for observations. In fact, since the Sun itself is not too bright at radio wavelengths, and these wavelengths do not brighten the sky in the same way, this telescope can even be used during the daytime, as long as it is not pointed towards the Sun. APEX is a 12-metre-diameter telescope that observes light at millimetre and submillimetre wavelengths. Astronomers observing with APEX can see phenomena which would be invisible at the shorter wavelengths of infrared or visible light. For instance, APEX can peer through dense interstellar clouds of gas and cosmic dust, revealing hidden regions of ongoing star formation which glow brightly ...
potw1302 — Picture of the Week
ALMA Dwarfed by Mountain Peaks
14 January 2013: At first glance, this view shows the mountainous scenery of Chile’s Chajnantor Plateau, with snow and ice scattered over the barren terrain. The main peaks from right to left are Cerro Chajnantor, Cerro Toco, Juriques, and the distinctive conical volcano Licancabur (see potw1240) —  impressive enough! However, the true stars of the picture are the tiny, barely visible structures in the very centre of the image — perceptible if you squint hard enough. These structures, dwarfed by their mountainous neighbours, are the antennas that form the Atacama Large Millimeter/submillimeter Array (ALMA), a large radio telescope. While it may appear minute in this image, the array is actually composed of a collection of large 12- and 7-metre-diameter antennas, and when it’s complete, there will be a total of 66 of them, spread over distances of up to 16 kilometres across the plateau. Construction work for ALMA is expected to finish in ...
potw1301 — Picture of the Week
Swirling Star Trails Over Yepun
7 January 2013: This view shows one of the Unit Telescopes of ESO’s Very Large Telescope (VLT) sitting beneath bright star trails circling the south celestial pole, a point in the sky that lies in the southern constellation of Octans (The Octant). These trails are arcs of light that trace out a star’s observed movement across the sky as the Earth slowly rotates. To capture these star trails on camera, many exposures were taken over time and combined to give the final appearance of circular tracks. Illuminated by moonlight, the telescope in the foreground is just one of the four Unit Telescopes (UTs) that make up the VLT at Paranal, Chile. Following the inauguration of the Paranal site in 1999, each UT was named in the language of the native Mapuche tribe. The names of the UTs — Antu, Kueyen, Melipal, and Yepun — represent four prominent and beautiful features of the sky: ...
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