Photo de la semaine 2009

23 mars 2009: Located inside the Large Magellanic Cloud (LMC) – one of our closest galaxies – in what some describe as a frightening sight, the Tarantula nebula is worth looking at in detail. Also known as 30 Doradus or NGC 2070, the nebula owes its name to the arrangement of its bright patches that somewhat resemble the legs of a tarantula. Taking the name of one of the biggest spiders on Earth is very fitting in view of the gigantic proportions of this celestial nebula — it measures nearly 1,000 light years across ! Its proximity, the favourable inclination of the LMC, and the absence of intervening dust make this nebula one of the best laboratories to better understand the formation of massive stars. This spectacular nebula is energised by an exceptionally high concentration of massive stars, often referred to as super star clusters. This image is based on data acquired with ...

9 mars 2009: The 40-metre-class primary mirror of the European Extremely Large Telescope (E-ELT) will be composed of 984 individual segments, which must be aligned with incredible precision. The position of the individual hexagonal mirrors needs to be controlled with nanometre precision (1 nanometre is 1 millionth of a mm). This can only be achieved with the help of new technologies and a prototype component for this high-tech alignment of segmented mirrors is seen in this image. The so-called Active Phasing Experiment achieved its First Light during the night of 6 December 2008 on the visitor focus of Melipal, one of the 8.2 m Unit Telescopes of ESO’s Very Large Telescope at Paranal. Made in collaboration with several European partners, the current active segmented mirror is composed of 61 hexagonal segments. You can move around the experiment in this Quicktime VTR animation.

2 mars 2009: One of most famous spiral galaxies is Messier 104, widely known as the "Sombrero" (the Mexican hat) because of its particular shape. It is located towards the constellation Virgo (the ‘virgin’), at a distance of about 30 million light-years and is the 104th object in the famous catalogue of deep-sky objects by French astronomer Charles Messier (1730 - 1817).This luminous and massive galaxy has a total mass of about 800 billion suns, and is notable for its dominant nuclear bulge, composed mainly of mature stars, and its nearly edge-on disc composed of stars, gas, and dust. The complexity of this dust is apparent directly in front of the bright nucleus, but is also evident in the dark absorbing lanes throughout the disc. A large number of small, diffuse objects can be seen as a swarm in the halo of Messier 104. Most of these are globular clusters, similar to those ...

23 février 2009: A view of Paranal from May 1987.

16 février 2009: The Bug Nebula, NGC 6302, is one of the brightest and most extreme planetary nebulae known. It is located about 4,000 light-years away, towards the Scorpius constellation (the Scorpion). The nebula is the swansong of a dying solar-like star lying at its centre. At about 250,000 degrees Celsius and smothered in a blanket of hailstones, the star itself has never been observed as it is surrounded by a dense disc of gas and dust, opaque to light. This dense disc may be the origin of the hourglass structure of the nebula. This colour image, which nicely highlights the complex structure of the nebula, is a composite of three exposures through blue, green and red filters. It was made using the 1.5-metre Danish telescope at the ESO La Silla Observatory, Chile.

9 février 2009: Cette image, prise tôt le matin il y a deux semaines, montre avec une grande clarté l'incroyable ciel au-dessus de Paranal, le siège du Very Large Telescope (VLT) de l'ESO au Chili. Le merveilleux paysage de la Voie lactée est suspendu dans toute sa splendeur au-dessus de trois des quatre télescopes auxiliaires (AT) de 1,8 mètre du VLT. Ils observent simultanément, en utilisant l'interférométrie pour obtenir une vision aussi nette que s'ils utilisaient un télescope d'un diamètre égal à la plus grande distance entre les télescopes, en l'occurrence 48 mètres. Comme les plus grands télescopes unitaires de 8,2 mètres du VLT sont généralement utilisés individuellement, les quatre AT ont été ajoutés au système afin d'utiliser pleinement le laboratoire d'interférométrie. La photo remarquable, orientée vers l'Est, montre les constellations Ophiuchus (le "porte-serpent"), Sagittaire (l'"archer"), Scorpion (le "scorpion") et Triangle Australe (le "triangle sud"). Le centre de la Voie lactée se trouve ...

2 février 2009: The pair of galaxies NGC 1531/2, engaged in a spirited waltz, is located about 70 million light-years away towards the southern constellation Eridanus (The River). The deformed foreground spiral galaxy laced with dust lanes NGC 1532 is so close to its companion — the background galaxy with a bright core just above the centre of NGC 1532 — that it gets distorted: one of its spiral arms is warped and plumes of dust and gas are visible above its disc. The cosmic dance leads to another dramatic effect: a whole new generation of massive stars were born in NGC 1532 because of the interaction. They are visible as the purple objects in the spiral arms. This exquisite image was made using the 1.5-metre Danish telescope at the ESO La Silla Observatory, Chile. It is based on data obtained through three different filters: B, V and R. The field of view ...

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 ...