Picture of the Week 2009

23 March 2009

The Tarantula Nebula

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 the 1.5 m Danish telescope at the ESO La Silla Observatory in Chile, through three filters (B: 80 s, V: 60 s, R: 50 s).


9 March 2009

First Light for the Active Phasing Experiment — a step towards the E-ELT

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 March 2009

The Sombrero Galaxy

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 found in our own Milky Way, but Messier 104 has a much larger number of them. This galaxy also appears to host a supermassive black hole of about 1 billion solar masses, one of the most massive black holes measured in any nearby galaxy, and 250 times larger than the black hole in the Milky Way. Despite having such a massive black hole at its centre, the galaxy is rather quiet, implying that the black hole is on a very stringent diet.

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: 120 s, V: 100 s, R: 100 s).


23 February 2009

Startrails over Cerro Paranal in 1987

A view of Paranal from May 1987.


16 February 2009

Cosmic Butterfly

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 February 2009

Beautiful Sky over Paranal *

This image, taken an early morning two weeks ago, shows with great clarity the amazing sky over Paranal, the home of ESO’s Very Large Telescope (VLT) in Chile.

The wonderful landscape of the Milky Way hangs in all its glory above three of the four 1.8-metre VLT Auxiliary Telescopes (ATs). They observe simultaneously, using interferometry to get a vision as sharp as if they used a telescope with a diameter equal to the largest distance between the telescopes, in this case, 48 metres. Because the larger 8.2-metre Unit Telescopes of the VLT are usually used individually, the four ATs have been added to the system to make full use of the interferometric laboratory.

Facing the East, the remarkable photo shows the constellations Ophiuchus (the ‘snake-holder’), Sagittarius (the ‘archer’), Scorpius (the ‘scorpion’), and Triangulum Australe (the ‘southern triangle’). The Centre of the Milky Way is just below the centre of the image.

This image is available as a mounted image in the ESOshop.


2 February 2009

Ballet of Interacting Galaxies

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 is 12 x 12 arcmin.


26 January 2009

Cleaning a VLT mirror

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 optician performing the cleaning, let the CO2 device touch the mirror, the fragile reflective Aluminium coating would be scratched. Also, hair or cloth lint should stay away from the mirror, which is why the optician is wearing a white suit made of special plastic. 


12 January 2009

The Trapezium Cluster

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 with the unaided eye, there is apparently no written record of its existence before the 17th century.

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: 60 s, V: 30 s, R: 21 s). East is at the upper right corner and North is at the lower right. 


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