Veckans bild 2013

25 mars 2013: I denna bild framträder galaxen NGC 4535 i stjärnbilden Jungfrun mot en vacker bakgrund av andra mer avlägsna galaxer. Galaxens runda uppsyn avslöjar att vi ser den nästan rakt ovanifrån. I dess mitt bildar galaxens stjärnor en tydlig stav, med mörka stoftstråk som vänder tvärt där staven slutar. Ett stort antal heta unga stjärnor gör att spiralarmarna lyser med en blåaktig färg. I mitten ligger galaxens bula; här är färgen snarare gul, tack vare äldre och svalare stjärnor. Bilden togs i synligt ljus med instrumentet FORS1 på ESO:s 8,2-metersteleskop VLT (Very Large Telescope). Galaxen, som också går att se med mindre amatörteleskop, observerades först av William Herschel år 1785. Genom ett amatörteleskop ser NGC 4535 dimmig och spöklik ut. Därför fick den på 1950-talet smeknamnet "The Lost Galaxy" (den borttappade galaxen) av den framstående amatörastronomen Leland S. Copeland. NGC 4535 är en av de största galaxerna i Virgohopen, en tung ...

18 mars 2013: Som sitt viktigaste tillbehör har forskningsteleskopen toppmoderna kameror som tillsammans med stora speglar gör det möjligt för astronomer att fånga upp det svaga ljuset från himlakroppar långt ut i rymden. Men det går faktiskt att skapa vackra bilder utan stora teleskop och med mer blygsamma kameror. Astrofotografer använder mindre avancerade kameror för att ta kort på astronomiska objekt, ofta i större skala än de stora teleskopens observationer. Ibland ingår landskapet i kompositionen och resultatet blir vackra vykort av universum så som det ser ut från jorden. Veckans bild, som är ett exempel på detta, visar 3,58-metersteleskopet NTT (New Technology Telescope) vid ESO:s La Silla-observatorium. Mest tydligt framträder vår hemgalax, Vintergatan, som ett dimmigt ljust band över himlen. De mörka områden inuti Vintergatan är ställen där ljuset från avlägsna stjärnor blockeras av stoft och damm mellan stjärnorna. Här syns även Stora magellanska molnet som en suddig fläck till höger om teleskopet. ...

11 mars 2013: Den här imponerande bilden togs av Gabriel Brammer, en av ESO:s fotoambassadörer. Den visar himlen efter solnedgången vid Paranalobservatoriet - och två kometer som just nu stryker över den södra stjärnhimlen. Nära horisonten till höger i bilden syns den ljusare av de två, komet C/2011 L4 (PAN-STARRS), som har en svans som lyser mest tack vare stoft och damm som reflekterar solens ljus. I bildens mitt, strax ovanför Paranalbergets sluttningar kan man urskilja det grönaktiga koma - gashöljet runt kometkärnan - hos kometen C/2012 F6 (Lemmon). Den har också en något ljussvagare svans. Den gröna färgen uppstår på grund av att gasen i kometens koma joniseras av solljuset. Man skulle nästan kunna tro att en tredje komet är synlig i bilden. Det ljusstarka objektet som svischar förbi mellan kometerna Lemmon och Pan-STARRS är istället ett stjärnfall: ett gruskorn som råkar ha brunnit upp i atmosfären vid precis rätt plats och ...

4 mars 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 ...

25 februari 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 ...

18 februari 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 ...

11 februari 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 ...

4 februari 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 ...

28 januari 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 ...

21 januari 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 ...

14 januari 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 ...

7 januari 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: ...