Photo de la semaine

26 janvier 2009: The 8.2m diameter main mirror of Antu, the first Unit Telescope of ESO's Very Large Telescope, is being cleaned using carbon dioxide snow. While the telescope enclosure is maintained extremely clean, the mirrors are exposed to the elements during the observations. Consequently, dust from the desert slowly accumulates over the surface of the mirror, making it less reflective over time. The mirror's surface is so delicate that normal cleaners used for household mirrors are not appropriate for telescopes. Observatories have developed other methods, such as this one using carbon dioxide snow. The tiny CO2 snowflakes in the white plume have a temperature of almost minus 80 degrees Celsius; when they land on the mirror, which is at room temperature, they cause minuscule 'explosions' that detach the dust grains from the surface. The dust then floats away, leaving the mirror clean. The process is nevertheless very delicate: should Alain Gilliotte, the ...

12 janvier 2009: The Orion Nebula is arguably the finest of all nebulae within the Milky Way visible from the Northern Hemisphere. With a gaseous repository of 10,000 suns, and illuminated by a cluster of hot young stars, the clouds of Messier 42 — as it is also known — glow with fantastic colours and shapes, giving us a bird’s eye view of one of the greatest star forming nurseries in our part of the Milky Way. Messier 42 is a complex of glowing gas, mostly hydrogen but also helium, carbon, nitrogen, and oxygen in decreasing amounts, located 1,500 light-years away. At its very heart, we find the Trapezium, a group of four very hot stars that illuminate the nebula. They are the brightest of an extended cluster of several thousand young stars many of which lie unseen within the opaque gas and dust. Amazingly, whilst the Orion Nebula is easy to identify ...

15 décembre 2008: The striking, large spiral galaxy NGC 1232, and its distorted companion shaped like the greek letter "theta". The pair is located roughly 60 million light-years away in the constellation Eridanus (The River). Billions of stars and dark dust are caught up in this beautiful gravitational swirl. The blue spiral arms with their many young stars and star-forming regions make a striking contrast with the yellow-reddish core of older stars. This image is based on data acquired with the 1.5 m Danish telescope at the ESO La Silla Observatory in Chile, through three filters (B: 900 s, V: 400 s, R: 400 s).

8 décembre 2008: About a year ago, ESO kindly agreed to donate a surplus van to the Colegio Hellen Keller, a school for children with visual disabilities, located in Santiago, Chile. The school was in desperate need of some form of transport as there were many children who could either not attend school at all, or had to spend the weekdays away from their family, simply because they could not make the daily journey on public transport, due to their disabilities. The initial idea was to donate one of the bus used to carry staff to Paranal. However, it became clear that this big van was not ideal for the school, especially with rising fuel prices. ESO kindly offered to donate the proceeds from the sale of the van instead, which was in excess of 4.000.000 Chilean Pesos (about 5,000 EUR). The school set up a fund to raise the rest of the ...

1 décembre 2008: Supernova 2008bk in the spiral galaxy NGC 7793 was discovered at the end of March 2008 by amateur astronomer Berto Monard from South Africa. The galaxy is 13 million light-years away in the direction of Sculptor constellation. This supernova is a typical example of a massive star that exploded at the end of its life. But this time, the astronomers were able not only to see the explosion, but to precisely pinpoint the star that exploded, a rather rare achievement. This was made possible because the explosion site had been observed several times with the help of ESO's Very Large Telescope, the latest images having been observed only a few months before the explosion with the new HAWK-I instrument. An European team of astronomers, led by Seppo Mattila of University of Turku, Finland, then observed the explosion site again two months after the supernova's discovery, this time with the VLT's ...

25 novembre 2008: Le Very Large Telescope (VLT) situé sur Cerro-Paranal à 2600 m d'altitude est le premier site utilisé par l'ESO pour les observations en lumière visible et l'infrarouge. Il est situé dans le desert d'Atacama au Chili. Les 4 télescopes unitaires (UT) de 8.2 m de diamètre peuvent être operés individuellement grâce à leur large collection d'instruments et ont déjà réalisé des découvertes scientifiques étonnantes. Le VLT offre la possibilité de combiner de facon cohérente la lumiere des 4 UTs pour etre utilisée en interféromètre. Le VLTI avec ces instruments permet d'effectuer des images de quelques mill-arcseconde ainsi que l'astrometrie d'une précision de 10 micro-arcescond. En plus des quatres télescopes de 8.2m , le VLTI utilise 4 telescopes auxilliaires (AT) de 1.8 m de diamètre ce qui permet d'augmenter les capacités d'imagerie et d'observer toute l'année. L'emplacement du dôme à venir du VLT "survey" télescope (2.6 m de diamètre) est visible ...

11 novembre 2008: The Carina Nebula is a large bright nebula that surrounds several clusters of stars. It contains two of the most massive and luminous stars in our Milky Way galaxy, Eta Carinae and HD 93129A. Located 7500 light years away, the nebula itself spans some 260 light years across, about 7 times the size of the Orion Nebula, and is shown in all its glory in this mosaic. It is based on images collected with the 1.5-m Danish telescope at ESO's La Silla Observatory. Being brighter than one million Suns, Eta Carinae (the brightest star in this image) is the most luminous star known in the Galaxy, and has most likely a mass over 100 times that of the Sun. It is the closest example of a luminous blue variable, the last phase in the life of a very massive star before it explodes in a fiery supernova. Eta Carinae is ...

4 novembre 2008: M1-67 is the youngest wind-nebula around a Wolf-Rayet star, called WR124, in our Galaxy. These Wolf-Rayet stars start their lives with dozens of times the mass of our Sun, but loose most of it through a powerful wind, which is ultimately responsible for the formation of the nebula. Ten years ago, Hubble Space Telescope observations revealed a wealth of small knots and substructures inside the nebula. The same team, led by Cédric Foellmi (ESO), has now used ESO's Very Large Telescope (VLT) to watch how these structures have evolved and what they can teach us about stellar winds, their chemistry, and how they mix with the surrounding interstellar medium, before the star will eventually blow everything away in a fiery supernova explosion. The image is based on FORS1 data obtained by the Paranal Science team with the VLT through 2 wide (B and V) and 3 narrow-band filters.

30 septembre 2008: A night of work for the Paranal Observatory, in the Chilean Atacama Desert. This picture, taken on 20 September, shows the incredible beauty of the night sky above the most advanced telescope in the world, ESO's Very Large Telescope. The Milky Way is clearly seen in this superb image.

22 septembre 2008: Composite colour-coded image of another magnificent spiral galaxy, NGC 7424, at a distance of 40 million light-years. It is based on images obtained with the multi-mode VIMOS instrument on the ESO Very Large Telescope (VLT) in three different wavelength bands. The image covers 6.5 x 7.2 square arcminutes on the sky. North is up and East is to the right. Read more about this superb object in the ESO Press Release eso0436.

21 août 2008: Image couleur composite de l’amas globulaire NGC 3201 obtenue au moyen de l’instrument WFI qui équipe le télescope ESO/MPG de 2,2 mètres installé à La Silla. Les amas globulaires sont de vastes agrégats d’étoiles susceptibles d’abriter des millions d’étoiles. Ils figurent parmi les objets les plus âgés de l’Univers et se sont probablement formés peu après le Big Bang, simultanément à la Voie Lactée. Cet amas globulaire se situe à quelque 16 000 années lumière de la Terre dans la constellation australe des Voiles. Les données ont été obtenues dans le cadre de l’ESO Imaging Survey (EIS), un sondage public mené par l’ESO et les états membres, en vue de préparer la Première Lumière du VLT. L’image originale et les données astronomiques peuvent être obtenues à partir des Pages de Publication des données du sondage EIS Pre-Flames. De nombreuses autres images sont également disponibles.

14 août 2008: The centre of our Milky Way galaxy is located in the southern constellation Sagittarius (The Archer) and is "only" 26,000 light-years away. On high-resolution images, it is possible to discern thousands of individual stars within the central, one light-year wide region. Using the motions of these stars to probe the gravitational field, observations over the last decade have shown that a mass of about 3 million times that of the Sun is concentrated within a radius of only 10 light-days of the compact radio and X-ray source SgrA* (Sagittarius A) at the centre of the star cluster. This means that SgrA* is the most likely counterpart of the black hole believed to exist at the centre of our Galaxy. This image was obtained in mid-2002 with the NACO instrument at the 8.2-m VLT Yepun telescope. It combines frames in three infrared wavebands between 1.6 and 3.5 µm. The compact objects ...

7 août 2008: Paranal, the site of the VLT, was chosen for its unique characteristics: extreme dryness, very low cloud coverage, high altitude, and distant from any source of pollution. This wide-angle shot of the Atacama desert around Paranal, which shows the VLT and, in foreground, VISTA, summarizes it all. Photo taken in November 2007.

30 juillet 2008: The "Very Large Telescope Video Collection 2008" features High Definition video material which was obtained in June 2008. For the first time, ESO distributes HD-footage of the world's most advanced ground-based observing facility and provides free access to video sequences of outstanding technical quality and beauty. The material has been edited especially for broadcast use, without commentary or music.

17 juillet 2008: The first successful movement of an ALMA antenna took place at the Operations Support Facility (OSF) on 8 July 2008. The antenna transporter "Lore", one of the two units manufactured by Scheuerle under contract by ESO and delivered recently at the OSF, has been used to move one 12-m antenna from their site erection facility to an external antenna pad for sky testing.

7 juillet 2008: Alors que ALMA est encore en construction, les astronomes font déjà de l'astronomie au millimètre et submillimètre à Chajnantor avec le Atacama Pathfinder Experiment (APEX). C'est un télescope nouvelle-téchnologie de 12 mètres, basé sur un prototype d'antenne ALMA et se trouvant sur le site d'ALMA. Cela a changé l'optique et augmenté la précision de la surface de l'antenne. Il est construit pour pouvoir profiter de l'excellent ciel transparent tout en travaillant sur des longueurs d'ondes allant de 0.2 a 1.4 mm. Cette image est disponible en tant qu'image murale à l'ESOshop.

1 juillet 2008: The image shows X-shooter, the first of the second generation VLT instruments, under test in the integration lab at ESO, Garching. The instrument has been built by a Consortium including ESO and institutes from Denmark, Italy, The Netherlands and France, and will start operation at the telescope in 2009. X-shooter is a single target, wide band, intermediate spectral resolution spectrograph, designed to get the full spectrum of the faintest cosmic sources from the atmospheric cutoff in the near-ultraviolet to the infrared K-band in a single exposure. In this image the instrument is shown as mounted on a telescope Cassegrain focus simulator, pointing at a large zenith distance. At the centre is the cryostat with the near-infrared arm of the spectrograph and at the left is the lower side of the visual spectrograph with its CCD detector. The two large boxes on the sides host the control electronics of the instrument.

23 juin 2008: The winding road connecting the ALMA Operation Support Facility at 3,000m altitude to the Array Operation Site (5,000m high) passes an area between 3500m and 3800m dominated by large cacti (Echinopsis Atacamensis). These cacti grow on average 1cm per year, and reach heights of up to 9m. Stephane Guisard recently captured the beautiful sky above this unique location in the Chilean Atacama Desert. The Milky Way is seen in all its glory, as well as, in the lower right, the Large Magellanic Cloud.

10 juin 2008: This aerial view of Cerro Paranal, the site of ESO's Very Large Telescope, was obtained in 1994. It shows the construction of the concrete base for the four telescope enclosures. To the left and a little lower than the rest of the platform is the excavation for the control building. The platform altitude is about 2640 metres above sea level and it measures about 150 metres across. The width of the access road is no less than 12 metres, i.e. nearly equal to that of a three-lane highway; this is necessary to ensure the safe transport of all telescope parts, especially the four 8.2-metre fragile mirrors, to the top. The summit of Paranal has been blasted away so to create the flat platform that supports the 4 Unit Telescopes, as well as the network of tunnels that transport the light from the telescopes to the interferometric laboratory. On this 1994 ...

26 mai 2008: Le ciel tournant au-dessus du Very Large Telescope à Paranal. Cette longue expositions montre les étoiles tournant autour des pôles célestes austral (gauche) et boréal (droite), l'équateur céleste étant au milieu de la photo, où les étoiles semblent bouger en ligne droite. Les mouvements des télescopes du VLT sont également visibles.