Picture of the Week 2010

22 March 2010

Dying Star Puffs a Cosmic Dragon

NGC 5189 is a planetary nebula with an oriental twist. Similar in appearance to a Chinese dragon, these red and green cosmic fireworks are the last swansong of a dying star.

At the end of its life, a star with a mass less than eight times that of the Sun will blow its outer layers away, giving rise to a planetary nebula. Some of these stellar puffballs are almost round, resembling huge soap bubbles or giant planets (hence the name), but others, such as NGC 5189 are more intricate.

In particular, this planetary nebula exhibits a curious “S”-shaped profile, with a central bar that is most likely the projection of an inner ring of gas discharged by the star, seen edge on. The details of the physical processes producing such a complex symmetry from a simple, spherical star are still the object of astronomical controversy. One possibility is that the star has a very close (but unseen) companion. Over time the orbits drift due to precession and this could result in the complex curves on the opposite sides of the star visible in this image.

This image has been taken with the New Technology Telescope at ESO’s La Silla Observatory in Chile, using the now decommissioned EMMI instrument. It is a combination of exposures taken through different narrowband filters, each designed to catch only the light coming from the glow of a given chemical element, namely hydrogen, oxygen and nitrogen.

15 March 2010

Solargraphy at Sunny Paranal

Solargraphy, the art of using a single long-term exposure with a pinhole camera to photograph the movement of the Sun over the course of many weeks, helps show just why Cerro Paranal in northern Chile makes the perfect home for ESO’s Very Large Telescope (VLT). The pinhole camera, made from a small film canister and a piece of photographic paper, was placed on the roof of the VLT control building by Gerd Hüdepohl from 15 October to 26 December 2009, covering spring in the southern hemisphere. The white streaks across the top of the image are the Sun’s progress across the sky over the whole period. When clouds come between the Sun and the camera, breaks in the streak form but, as can be seen here, no clouds obscured the sky during the entire exposure. Perfect astronomy weather in other words! The VLT’s Unit Telescope 1 is visible as a ghostly outline at the bottom of the picture.

The idea for creating the solargraphs at ESO’s telescopes came from Bob Fosbury, an astronomer based at ESO headquarters in Germany, after learning about the technique from Finnish artist Tarja Trygg. Trygg provided cameras — basically cylinders with a hole and a piece of unexposed photographic paper mounted along the inner wall — and Fosbury had Observatory director Andreas Kaufer deliver the cameras, known as “cans”, to ESO’s observatory sites in Chile and then collect them four months later for final processing by Trygg. “It’s an absolutely unique image,” Fosbury says. “I’ve never seen unbroken solar trails like this before in images exposed from all around the world.

 The colours appearing in this pinhole camera picture are not related to the actual colours of the scene. The colour comes from the appearance of finely divided metallic silver growing on silver halide grains. With solargraphic images, the photographic paper is not developed but simply scanned with a normal colour scanner after exposure and then “inverted” — switched from negative to positive — in the computer. This reveals the latent image, which in a normal photograph consists of around ten silver atoms per billion atoms of silver halide grain and is usually invisible. On continued exposure however, the latent image clumps grow so that the first visible signs of an image are yellowish, which then darkens to sepia and finally to a maroonish-brown hue as the particle size increases. Eventually the maximum exposure produces a slate grey shade.

In this solargraph you can see curved reflections of the solar image forming a “caustic” about one third of the way across the image. Such effects are common in solargraphs when the Sun is near the edge of the field and are created by reflections from the white paper where the photographic paper departs from a circle and flattens near its ends.


8 March 2010

Snowy ESO Headquarters*

The European Southern Observatory’s Headquarters chills out in the snow beneath the full Moon one late afternoon in January. The winter snows at the Garching technical campus north of Munich, Germany make a stark contrast to the dry deserts of ESO’s observatories in Chile.

ESO Headquarters is the scientific, technical and administrative centre of ESO and is where technical development programmes are carried out, providing the observatories with the most advanced instruments in the world. It is also home to the Space Telescope — European Coordinating Facility, operated jointly by ESO and the European Space Agency.

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

1 March 2010

Darth Vader’s Galaxy, NGC 936

Glowing in the cosmos at a distance of about 50 million light-years away, the galaxy NGC 936 bears a striking resemblance to the Twin Ion Engine (TIE) starfighters used by the evil Dark Lord Darth Vader and his crew in the epic motion picture Star Wars. The galaxy’s shiny bulge and a bar-like structure crossing it bring to mind the central engine and cockpit of the spacecraft; while a ring of stars surrounding the galactic core completes the parallel, corresponding to the wings of the TIE fighters that are equipped with solar panels.

This galaxy harbours exclusively old stars and shows no sign of any recent star formation. Bars such as that observed in NGC 936 are common features of galaxies; however, this one is significantly more marked than average. Although a perfect symbol for the dark side of the “Force”, it is still debatable whether this galaxy is dominated, like most others, by a large amount of dark matter.

This image has been obtained using the FORS instrument mounted on one of the 8.2-metre telescopes of ESO’s Very Large Telescope on top of Cerro Paranal, Chile. It combines data acquired through four wide-band filters (B, V, R, I). The field of view is about 7 arcminutes.

22 February 2010

A Dwarf in the Fornax Cluster

In this dazzling image, the galaxy NGC 1427A is seen as it travels through the Fornax cluster of galaxies, to which it belongs. NGC 1427A is an example of a dwarf irregular galaxy, a type of galaxy that is significantly less bright than regular galaxies and characterised by a peculiar shape. In this particular case, the shape of the galaxy has been forged by its rapid, upwards motion through the cluster: with a speed of two million kilometres per hour relative to the cluster, NCG 1427A is being torn apart and will eventually be disrupted.

The interaction with the Fornax cluster has led to the birth of many stars, seen here as a boomerang-shaped region of young, glowing stars in the galaxy. NGC 1427A exhibits a striking resemblance to one of our galactic neighbours, the Large Magellanic Cloud, which has undergone similar episodes of star formation, triggered by its interaction with the Milky Way.

This image has been obtained using the FORS instrument mounted on one of the 8.2-metre telescopes of ESO’s Very Large Telescope on top of Cerro Paranal, Chile. It combines data acquired through four broadband filters (U, B, V, I) and a narrowband one (H-alpha). 

North is on the left and West is up. The field of view is 7 arcminutes.

15 February 2010

The Hidden Engine of NGC 4945

Portrayed in this image is the spiral galaxy NGC 4945, a close neighbour of the Milky Way. Belonging to the Centaurus A group of galaxies, it is located at a distance of almost 13 million light-years. Showing a remarkable resemblance to our own galaxy, NGC 4945 also hides a supermassive black hole behind the thick, ring-shaped structure of dust visible in the picture. But, unlike the black hole at the centre of our Milky Way, the million-solar-mass black hole inside NGC 4945 is an Active Galactic Nucleus that is frantically consuming any surrounding matter, and so releasing tremendous amounts of energy.

This image combines observations performed through three different filters (B, V, R) with the 1.5-metre Danish telescope at the ESO La Silla Observatory in Chile.

8 February 2010

Bird’s Eye View of the Very Large Telescope*

A bird soaring over the remote, sparsely populated Atacama Desert in northern Chile — possibly the driest desert in the world — might be surprised to come upon the technological oasis of ESO’s Very Large Telescope (VLT) at Paranal. The world’s most advanced ground-based facility for astronomy, the site hosts four 8.2-metre Unit Telescopes, four 1.8-metre Auxiliary Telescopes, the VLT Survey Telescope (VST), and the 4.1-metre Visible and Infrared Survey Telescope for Astronomy (VISTA), seen in the distance on the next mountain peak over from the main platform.

This aerial view also shows other structures, including the Observatory Control Room building, on the main platform’s front edge.

1 February 2010

Paranal from on High

This aerial photograph shows the summit of Cerro Paranal in northern Chile, the home of ESO’s Very Large Telescope (VLT). This flagship facility for ground-based astronomy hosts four 8.2-metre Unit Telescopes along with four mobile 1.8-metre Auxiliary Telescopes. These can work together, in groups of two or three, as one giant telescope, known as the VLT Interferometer, or VLTI.

This image displays the winding access road that leads up to the observing platform as well as the Observatory Control Room in the front. The picture helps give a sense of the remoteness of the VLT site, which is located in the extremely arid Atacama Desert at an altitude of 2600 metres. The first Unit Telescope began operations at Paranal in 1999. The VLT Survey Telescope, which is scheduled to begin observations in 2010, is missing from this photo, taken in 2004.

25 January 2010

Vertical panorama of the ESO 3.6-metre telescope

This impressive vertical panorama shows the ESO 3.6-metre telescope in great detail. The telescope is located on the 2400 m high La Silla mountain, home of ESO’s first observing site in the southern edges of the Atacama Desert. Equipped with HARPS, the best exoplanet finder in the world, the ESO 3.6-metre telescope was commissioned in 1977 and completely upgraded in 1999. The primary mirror is located below the dark protective cover, and the large black structure above holds the secondary mirror. The white cube on top of the secondary mirror mount contains the computer that controls the secondary mirror.

18 January 2010

The Future European Extremely Large Telescope

This architectural concept drawing of ESO’s planned European Extremely Large Telescope (E-ELT) shows the world’s largest planned optical telescope gazing heavenwards. Slated to begin operations early in the next decade, the E-ELT will tackle the biggest scientific challenges of our time. A chief goal will be to track down Earth-like planets around other stars in the “habitable zones” where life could exist — one of the Holy Grails of modern observational astronomy. The E-ELT will also make fundamental contributions to cosmology by measuring the properties of the first stars and galaxies and probing the nature of dark matter and dark energy.

On top of this, astronomers are also planning for the unexpected — new and unforeseeable questions will surely arise from the discoveries made with the E-ELT. With a primary mirror measuring an astounding 39 metres across, the E-ELT will collect 25 times more light than one 8.2-metre telescope at ESO’s Very Large Telescope observatory in Chile, which is currently a world leader in terms of astronomical observational capacity.

The design for the E-ELT shown here was published in 2011 and is preliminary.

11 January 2010

Zodiacal Light over La Silla

This image beautifully captures the zodiacal light, a triangular glow seen best in night skies free of overpowering moonlight and light pollution. The photograph was taken at ESO’s La Silla Observatory in Chile in September 2009, facing west some minutes after the Sun had set. A sea of clouds has settled in the valley below La Silla, which sits at an altitude of 2400 metres, with lesser peaks and ridges poking through the mist.

The zodiacal light is sunlight reflected by dust particles between the Sun and Earth, and is best seen close to sunrise or sunset. As its name implies, this celestial glow appears in the ring of constellations known as the zodiac. These are found along the ecliptic, which is the eastward apparent “path” that the Sun traces across Earth’s sky.

4 January 2010

The Heart of a Powerful Telescope *

This image shows the interior of one of the four 8.2-metre Unit Telescopes at ESO’s Very Large Telescope (VLT) in Paranal, Chile. Designated Unit Telescope 1, or UT1, and named Antu, this complex science machine has been in operation at Paranal since 1999. Just before sunset, technicians retract UT1’s windshield and work to finalise the preparations at the telescope for the night-time observation run. During the day, the enclosure is kept shut to protect the delicate and valuable scientific equipment inside, as well as to ensure minimal temperature differences between the telescope and the atmosphere at opening.

To the left of the telescope’s main mirror housing, in the centre of the image, is the Infrared Spectrometer And Array Camera (ISAAC), which was, until recently, attached to this instrument. It has now been moved to another of the Unit Telescopes, UT3 or Melipal.

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

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