Picture of the Week

2 April 2012

La Silla, the First Home for ESO’s Telescopes — ESO’s first observatory site Then and Now

ESO turns fifty this year, and to celebrate this important anniversary, we are showing you glimpses into our history. Once a month during 2012, a special Then and Now comparison Picture of the Week shows how things have changed over the decades at the La Silla and Paranal Observatory sites, the ESO offices in Santiago de Chile, and the Headquarters in Garching bei München, Germany.

This historical image was taken around 1970 from the La Silla dormitories, located lower on the mountain than the telescope domes. The photo looks up towards the highest point of the mountain, on the left. The metallic structure visible near the top of this peak is not a telescope, but a water tank for the site. The white dome in the centre of the image is that of the ESO 1-metre Schmidt telescope, which started work in February 1972. On the far right of the image is the ESO 1-metre telescope, just visible over the ridge, and to the left of that one can just see the top of the Grand Prisme Objectif telescope.

In the present-day photograph, the dormitory buildings remain, but more have been built over the decades. The most striking changes, though, are visible around La Silla’s peak on the left. At the highest point is the ESO 3.6-metre telescope, which started operating in November 1976 and is still in use today. The 3.6-metre is home to HARPS, the foremost exoplanet hunter (see eso1134 and eso1214 for some recent results). The 3.6-metre, planned from the inception of ESO, was to crown the La Silla Observatory as its biggest telescope, and was a major engineering feat of its time. The smaller dome visible in front of the 3.6-metre is the 1.4-metre Coudé Auxiliary Telescope, which complemented its bigger neighbour.

To the right of the 3.6-metre is the 3.58-metre New Technology Telescope (NTT), recognisable by the angular, metallic appearance of its enclosure. The NTT, which started operating in March 1989, was the first telescope in the world to use a computer-controlled mirror. It was used as a precursor for the Very Large Telescope, to test many new technologies that were then used in the later telescope.

Other new sights in the modern-day photograph are the workshop building below the water tanks, and the Differential Image Motion Monitor (DIMM), used to measure the atmospheric seeing, located on stilts between the workshop and the ESO 1-metre Schmidt telescope.

Even today, La Silla remains a very active observatory where important discoveries are made. Both the NTT and the 3.6-metre telescope provided vital data which led to the discovery of the accelerating expansion of the Universe — a discovery for which the 2011 Nobel Prize in Physics was awarded.


26 March 2012

Wish You Were Here?

French photographer Serge Brunier — one of ESO’s Photo Ambassadors — has created this seamless 360-degree panorama of the Chajnantor plateau in the Atacama Desert, where the Atacama Large Millimeter/submillimeter Array (ALMA) is under construction.

The panorama projection has slightly warped the shapes of the ALMA antennas, but it still gives a sense of what it would be like to stand in the middle of this impressive new observatory. The 360 degree panorama view also demonstrates the complete isolation of the Chajnantor plateau; at an altitude of 5000 metres, the backdrop is almost featureless, except for a few mountain peaks and hilltops.

Although constructing such an ambitious telescope project in a remote and harsh environment is challenging, the high altitude location is perfect for submillimetre astronomy.  That’s because water vapour in the atmosphere absorbs this type of radiation, but the air is much drier at high altitude sites such as Chajnantor.

ALMA started its first scientific observations on 30 September 2011 with a partial array of antennas. When the observatory is completed, the impressive sight of fifty 12-metre antennas — as well as a smaller array of four 12-metre and twelve 7-metre antennas, known as the Atacama Compact Array (ACA) — will make the isolated landscape seem slightly less empty. In the meantime, photographs like this one are documenting the progress of a new world-class telescope facility.

ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.


19 March 2012

The VLT goes lion hunting

The Very Large Telescope has captured another member of the Leo I group of galaxies, in the constellation of Leo (The Lion). The galaxy Messier 95 stands boldly face-on, offering an ideal view of its spiral structure. The spiral arms form an almost perfect circle around the galactic centre before they spread out, creating a mane-like effect of which any lion would be proud.

Another, perhaps even more striking, feature of Messier 95 is its blazing golden core. It contains a nuclear star-forming ring, almost 2000 light-years across, where a large proportion of the galaxy’s star formation takes place. This phenomenon occurs mostly in barred spiral galaxies such as Messier 95 and our home, the Milky Way.

In the Leo I group, Messier 95 is outshone by its brother Messier 96 (see potw1143). Messier 96 is in fact the brightest member of the group and — as “leader of the pride” — also gives Leo I its alternative name of the M 96 group. Nevertheless, Messier 95 also makes for a spectacular image.

Stop press! By coincidence Messier 95 is the host of a probable supernova that was first spotted on 17 March 2012. Discovery details are here. And as another coincidence both supernova and galaxy are currently very close to the brilliant planet Mars amongst the stars of Leo. Please note that the observations used to make this Picture of the Week were taken before the supernova occurred, and therefore the supernova itself does not appear in this image.

12 March 2012

A Dusting of Snow in the Atacama Desert

The domes of ESO’s Very Large Telescope sit atop Cerro Paranal, basking in the sunlight of another glorious cloudless day. But something is different about this picture: a fine layer of snow has settled across the desert landscape. This isn’t something you see every day: quite the opposite in fact, as the Atacama Desert gets almost no precipitation.

Several factors contribute to the dry conditions in the Atacama. The Andes mountain range blocks rain from the east, and the Chilean Coast Range from the west. The cold offshore Humboldt current in the Pacific Ocean creates a coastal inversion layer of cool air, which prevents rain clouds from developing. 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 dry. Thanks to all these factors, the region is widely regarded as the driest place on Earth!

At Paranal, the precipitation levels are usually just a few millimetres per year, with the humidity often dropping below 10%, and temperatures ranging from -8 to 25 degrees Celsius. The dry conditions in the Atacama Desert are a major reason why ESO chose it, and Cerro Paranal, to host the Very Large Telescope. While the very occasional snowfall may temporarily disrupt the dry conditions here, it does at least produce unusual views of rare beauty.

This photograph was taken by ESO Photo Ambassador Stéphane Guisard on 1 August 2011.


5 March 2012

A Window to the Past — La Silla’s transformation through time

ESO turns fifty this year, and to celebrate this important anniversary, we are showing you glimpses into our history. Once a month during 2012, a special “Then and Now” comparison Picture of the Week shows how things have changed over the decades at the La Silla and Paranal observatory sites, the ESO offices in Santiago de Chile, and the Headquarters in Garching bei München, Germany.

Here are two photographs of La Silla, taken in June 1968 and the present day from near the observatory’s water tanks, looking over the rest of the site. You can examine the changes with our mouseover image comparison.

In the historical image, the provisional residential area is visible in the foreground. The three telescopes in the background are, from left to right, the Grand Prism Objectif (GPO, first light in 1968), the ESO 1-metre telescope (first light in 1966), and the ESO 1.5-metre telescope (first light in 1968). These three telescopes were the first at La Silla. The white dome closest to the viewer is the ESO 1-metre Schmidt telescope, which began work in 1971.

Today, these four domes are still present, but the first three telescopes have been decommissioned. The ESO 1-metre Schmidt is still in operation, but is now a project telescope dedicated to the LaSilla–QUEST Variability survey (see potw1201a).

The present-day photograph also shows two new telescopes. The silver dome is that of the MPG/ESO 2.2-metre telescope, which has been in operation since early 1984 and is on indefinite loan to ESO from the Max-Planck-Gesellschaft. On the far left is the Danish 1.54-metre telescope, in use since 1979, which is one of several national telescopes at La Silla.


27 February 2012

Spinning into Action

The dynamism of ESO's Very Large Telescope in operation is wonderfully encapsulated in this unusual photograph, taken just after sunset at the moment Unit Telescope 1 starts work. An extended exposure time of 26 seconds has allowed ESO Photo Ambassador Gerhard Hüdepohl to record the movement of the dome, looking out through the opening from within, as the system swings into action. The rotating walls of the dome look like an ethereal swirl through which a slice of the Atacama Desert can be glimpsed, while the crisp dusk sky provides a splash of cool blue.

The telescope structure, seen stationary in the centre of the image, houses a mirror 8.2 metres in diameter, designed to collect light from the far reaches of our Universe. The dome itself is also an engineering marvel, moving with extreme precision and allowing for careful temperature control lest warm air currents disrupt observations.


20 February 2012

Boldly going up Cerro Paranal

ESO’s Paranal Observatory facilities, such as the Residencia, give people who work at the site a welcome shelter from the surrounding inhospitable environment. In spite of that, they also offer interesting options for those who wish to enjoy the stark and silent beauty of the Atacama Desert. See this stunning panorama!

Among these is the Star Track, a walking path which connects the Residencia with the Very Large Telescope (VLT) platform, on the 2600-metre summit of Cerro Paranal. Built in 2001, the Star Track covers about two kilometres in distance and a difference in height of 200 metres. The last part of the track snakes around the west side of the mountain, offering incomparable views.

This 360 degree panoramic picture is centred facing north, so the right and left edges of the picture correspond to the south. To the north, the VLT control room and part of one of the Unit Telescope enclosures can just be seen peeking over a local bump in the terrain that hides most of the Paranal summit. To the west, clouds cover the Pacific Ocean, only 12 kilometres away. To the east, the facade and dome of the Residencia can be seen in the distance.


13 February 2012

The Heart of the Milky Way, for Valentine’s Day

There is a lot to love about astronomy, and — in time for Valentine's Day — photographer Julien Girard offers a "heartfelt” example in this image. A bright pink symbol of love appears to float ethereally against the backdrop of the night sky over ESO's Paranal Observatory in northern Chile. Girard drew the heart in the air by shining a tiny flashlight keychain at the camera during a 25-second exposure with a tripod.

The central region of the Milky Way appears in the middle of the heart, as the plane of our galaxy stretches across the image. The stars of the constellation of Corona Australis (The Southern Crown) form a glittering arc of jewels at the top of the heart's left lobe. The diffuse glow to the left of the heart's lowest point is zodiacal light, caused by the scattering of light from the Sun by dust particles in the Solar System.

On the far right horizon, the 8.2-metre telescopes of the ESO Very Large Telescope (VLT) facility stand out in silhouette atop Cerro Paranal. The lights of a car driving down from the observatory platform can be seen just to the left of the telescopes.

Julien Girard is an ESO astronomer based in Chile, who works at the VLT. He is the instrument scientist for the NACO adaptive optics instrument on the VLT’s Unit Telescope 4. He submitted this photograph to the Your ESO Pictures Flickr group, from where it was picked out as an ESO Picture of the Week.


6 February 2012

A Drive Through Time — How telescopes, and cars, have changed at La Silla

ESO turns fifty this year, and to celebrate this important anniversary, we are showing you glimpses into its history. Once a month during 2012, a special “Then and Now” comparison Picture of the Week shows how things have changed over the decades at the La Silla and Paranal observatory sites, the ESO offices in Santiago de Chile, and the Headquarters in Garching bei München, Germany.

These two photographs show the La Silla Observatory in the late 1960s and the present day. You can also examine the differences between the two photographs with our mouseover comparison. The telescopes aren’t the only things that have changed; the cars in the photos also show the passing of time. The Volkswagen 1600 Variant in the first picture has been replaced in the second picture by a Suzuki 4WD. Nowadays, all ESO vehicles on La Silla are white, to improve visibility at night.

Standing alone in the centre of the historical image is the ESO 1-metre Schmidt telescope, which began work in 1971. Back then, it used photographic plates to take wide-field images of the southern sky four degrees across — large enough to fit the full Moon 64 times over. The huts lining the road to the right of the image are where astronomers used to sleep.

Fast forward to 2011 and another two telescopes appear. On the left is the MPG/ESO 2.2-metre telescope, which has been in operation since 1984. In fact, its construction is why the modern-day photograph could not be taken from exactly the same place! On the peak to the right is the New Technology Telescope (NTT) commissioned later in 1989. Both these telescopes have had enormous successes over the years and are still in operation today. And the huts for the astronomers have in the meantime been replaced with a more comfortable “hotel” on the edge of the site.

As for the Schmidt telescope, still standing in the middle, its original photographic camera was decommissioned in December 1998, but it lives on as a project telescope. It is being used to conduct the LaSilla–QUEST Variability survey: a search for so-called transient objects in the southern sky, such as new Pluto-sized dwarf planets, or supernovae. Its new camera has a mosaic of 112 CCDs, with a total of 160 million pixels — an excellent example of how modern technology can give an old telescope a new lease of life!


30 January 2012

A Shadow at Sunrise

In this photograph, taken by ESO Photo Ambassador Gianluca Lombardi, the Sun is rising and bathing the Chilean Atacama Desert in a familiar soft reddish glow. But this image, from 13 July 2011, has also captured something out of the ordinary: a dark shadow lurking on the horizon.

Gianluca took this photograph from Cerro Armazones, looking west. Armazones is the future home of the world’s biggest eye on the sky: the upcoming European Extremely Large Telescope (E-ELT). The Sun rose behind Gianluca in just the right place to cast a daunting shadow of the 3060-metre-high mountain onto the Earth’s atmosphere in the distance. The shadow can be seen reaching over the vast desert landscape, and up across the horizon on the left side of the image.

The bright summit visible on the right of the image is Cerro Paranal, at an altitude of 2600 metres. It is only 20 kilometres from Cerro Armazones, and is the home of ESO’s Very Large Telescope. Both sites have exceptional astronomical observing conditions. To its right is the adjacent peak where the VISTA survey telescope is located and to its left, on the horizon, are the Paranal Observatory’s basecamp and Residencia.

The white road winding across the bottom-left corner of the photograph is the route to the summit of Cerro Armazones.


  • This image, as well as many more stunning shots from Gianluca Lombardi, can be found on his Flickr photostream.
  • Find out more about the ESO Photo Ambassadors here.
  • Find out more about Cerro Armazones and the E-ELT here.

23 January 2012

Barred Spiral Galaxy Swirls in the Night Sky

This image shows the swirling shape of galaxy NGC 2217, in the constellation of Canis Major (The Great Dog). In the central region of the galaxy is a distinctive bar of stars within an oval ring. Further out, a set of tightly wound spiral arms almost form a circular ring around the galaxy. NGC 2217 is therefore classified as a barred spiral galaxy, and its circular appearance indicates that we see it nearly face-on.

The outer spiral arms have a bluish colour, indicating the presence of hot, luminous, young stars, born out of clouds of interstellar gas. The central bulge and bar are yellower in appearance, due to the presence of older stars. Dark streaks can also be seen in places against the galaxy’s arms and central bulge, where lanes of cosmic dust block out some of the starlight.

The majority of spiral galaxies in the local Universe — including our own Milky Way — are thought to have a bar of some kind, and these structures play an important role in the development of a galaxy. They can, for example, funnel gas towards the centre of the galaxy, helping to feed a central black hole, or to form new stars.

16 January 2012

ALMA’s Grand Antennas

Workers on the Atacama Large Millimeter/submillimeter Array (ALMA) project stand next to three of the telescope’s antennas. This photograph gives a real sense of the scale of the giant dishes, whose 12-metre diameters are about seven times the average human height. When completed, ALMA will consist of 66 high-precision antennas, 54 of them with 12-metre dishes as seen in this image, and 12 more compact ones with diameters of 7 metres. The yellow 28-wheel transporter vehicle, which has to be powerful enough to carry the 100-tonne antennas, is built on a similarly giant scale.

This photograph was taken at the 2900-metre-high ALMA Operations Support Facility in the foothills of the Chilean Andes, where the antennas are assembled and tested. On the left is one of the European ALMA antennas, pointing at the horizon. Behind it is one of the antennas provided to the project by Japan, while on the right, on the transporter vehicle and pointing upwards, is another European antenna. This is the first European antenna starting its journey up to the Array Operations Site on the Chajnantor plateau, photographed in July 2011 (see eso1127). Since this photograph was taken, the antennas, and others like them, have been put into operation on Chajnantor as ALMA has made its first scientific observations (see eso1137). ALMA is designed to study the cool Universe — the relic radiation of the Big Bang and the molecular gas and dust from which stars, planets and galaxies originate.

ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Twenty-five European ALMA antennas are being provided by ESO through a contract with the European AEM Consortium. ALMA will also have 25 antennas provided by North America, and 16 by East Asia.

9 January 2012

Mapping Dark Matter in Galaxies

The picture is part of the COMBO-17 survey (Classifying Objects by Medium-Band Observations in 17 Filters), a project dedicated to recording detailed images of small patches of the sky through filters of 17 different colours. The area covered in this image is only about the size of the full Moon, but thousands of galaxies can be identified just within this small region.

The image was taken with an exposure time of almost seven hours, which allowed the camera to capture the light from very faint and distant objects, as well as those that are closer to us. Galaxies with clear and regular structures, such as the spiral specimen viewed edge-on near the upper left corner, are only up to a few billion light-years away. The fainter, fuzzier objects are so far away that it has taken nine or ten billion years for their light to reach us.

The COMBO-17 survey is a powerful tool for studying the distribution of dark matter in galaxies. Dark matter is a mysterious substance that does not emit or absorb light and can only be detected by its gravitational pull on other objects. Some of the closer galaxies pictured act as lenses that distort the light coming from more distant galaxies placed along the same line of sight. By measuring this distortion, an effect known as gravitational lensing, astronomers are able to understand how dark matter is distributed in the objects that act as lenses.

The distortion is weak and, therefore, almost imperceptible to the human eye. However, because surveying the sky with 17 filters allows extremely precise distance measurements, it is possible to determine if two galaxies that appear to lie close to each other are actually at very different distances from the Earth. After identifying the galactic lensing systems, the distortion can be measured by averaging over thousands of galaxies. With more than 4000 galactic lenses identified, this COMBO-17 survey is an ideal method to help astronomers to understand the dark matter better.

This image was taken with three of the 17 filters from the project: B (blue), V (green), and R (red). Data through an additional near-infrared filter was also used. 


3 January 2012

A Glimpse into the Past — Then and Now at La Silla Observatory

ESO turns 50 this year, and to celebrate this important anniversary, we will be showing you glimpses into our history. Once a month throughout 2012, a special “then and now” comparison Picture of the Week will show how things have changed over the decades at the La Silla and Paranal observatory sites, the ESO offices in Santiago de Chile, and the Headquarters in Garching bei München, Germany.

Our first stop on this journey through time is at La Silla, the first of ESO’s observatory sites. The historical image was taken in the late 1960s or early 1970s from the dome of the ESO 1.52-metre telescope, which had its first light in 1968. A second photograph, taken in the present day, shows how much the observatory has changed over the decades. You can examine the changes with our mouseover image comparison.

In the historical image, we can see the ESO 1-metre telescope in the foreground on the right, with the Grand Prism Objectif telescope (GPO) just peeking out from behind. The third telescope in this photo is the Schmidt 1-metre telescope, on the left. Behind it, at a higher level, are the water tanks of the observatory.

Moving through time to the present-day, we can see how much La Silla has evolved, with many more telescopes on the site. The ESO 3.6-metre telescope and the adjacent Coudé Auxiliary Telescope now stand out on the highest peak. The angular enclosure of the New Technology Telescope (NTT) is just to the left, next to the water tanks. The 15-metre-diameter dish of the Swedish–ESO Submillimetre Telescope (SEST) watches the horizon on the far right.

The new photograph was taken from a slightly different position on top of the ESO 1.52-metre telescope building, so the GPO is now hidden behind the ESO 1-metre telescope in the foreground. The white dome that is just visible behind the 1-metre is the Danish 1.54-metre telescope. In the centre of the photo we now see the silvery dome of the MPG/ESO 2.2-metre telescope.

Although some telescopes at La Silla, such as the ESO 1-metre and 1.52-metre, and the SEST, are no longer in operation, others are still doing front-line astronomy. The ESO 3.6-metre telescope hosts the HARPS instrument, the world’s leading exoplanet hunter (see eso1134 for some recent results). The NTT has been used to help explain the formation of massive stars (see eso1029). Both telescopes provided vital data which led to the discovery of the accelerating expansion of the Universe — a discovery for which the 2011 Nobel Prize in Physics was awarded. The MPG/ESO 2.2-metre telescope has also produced a treasure trove of data from breathtaking wide-field images to studies of gamma-ray bursts, the most explosive events in the Universe.


26 December 2011

Inside Euler's Head — Or how to see a telescope through the walls of its dome

As night was falling over ESO’s La Silla Observatory in Chile on 20 December 2009, the sky was not yet dark enough for the telescopes to start observations. But conditions were perfect to perform a clever trick with the dome of the Swiss 1.2-metre Leonhard Euler Telescope: allowing us to peer inside with this photograph apparently taken through the dome.

This image is a 75-second exposure taken while the slit of the Euler telescope’s dome was performing half a rotation at full speed. Through the ghostly blur of the moving dome walls, the telescope is clearly visible. A dim light was switched on in the interior of the building especially for the purpose of this photo.

The picture was taken by Malte Tewes, a young astronomer from the École Polytechnique Fédérale de Lausanne in Switzerland, who had just finished a two-week observing run at the telescope on the evening in question. The next observer, Amaury Triaud, and the telescope’s technician, Vincent Mégevand (both pictured), were on site so they could operate the dome from the inside while Malte took the photograph from outside.

The road that leads to ESO’s nearby 3.6-metre telescope is visible lined by a chain of lights to the left of the image. In addition to the 3.6-metre telescope, the New Technology Telescope, and the MPG/ESO 2.2-metre telescope, La Silla Observatory also hosts several national and project telescopes that are not operated by ESO. The Euler telescope, named after the famous Swiss mathematician Leonhard Euler, is one of them.


19 December 2011

Llullaillaco, Clear as Day

Bathed in the pristine light of the Chilean Atacama Desert, the ESO VLT’s Auxiliary Telescope 2 stands on Cerro Paranal. It is one of four that are used with the Very Large Telescope Interferometer. During the day, its bulbous dome is closed, protecting the sensitive telescope within.

The magnificent 6739-metre volcano Llullaillaco stands proudly in the background of this photograph. Although it looks relatively close on the horizon, it is actually an incredible 190 kilometres away, on the border with Argentina. That Llullaillaco can be seen so clearly is evidence of the region’s unparallelled atmospheric conditions. The clear air is one of the many factors that make this such a wonderful location for astronomical observatories. It is from this excellent vantage point that ESO astronomers study objects that are not just hundreds of kilometres in the distance, but billions of light-years away.

This photograph was taken by ESO Photo Ambassador Gianluca Lombardi.


12 December 2011

ALMA's World At Night

This panoramic view of the Chajnantor plateau, spanning about 180 degrees from north (on the left) to south (on the right) shows the antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) ranged across the unearthly landscape. Some familiar celestial objects can be seen in the night sky behind them. These crystal-clear night skies explain why Chile is the home of not only ALMA, but also several other astronomical observatories. This image is just part of an even wider panorama of Chajnantor.

In the foreground, the 12-metre diameter ALMA antennas are in action, working as one giant telescope, during the observatory’s first phase of scientific observations. On the far left, a cluster of smaller 7-metre antennas for ALMA’s compact array can be seen illuminated. The crescent Moon, although not visible in this image, casts stark shadows over all the antennas.

In the sky above the antennas, the most prominent bright “star” — on the left of the image — is in fact the planet Jupiter. The gas giant is the third brightest natural object in the night sky, after the Moon and Venus. The Large and Small Magellanic Clouds can also be clearly seen on the right of the image. The Large Magellanic Cloud looks like a puff of smoke, just above the rightmost antenna. The Small Magellanic Cloud is higher in the sky, towards the upper-right corner. Both “clouds” are in fact dwarf irregular galaxies, orbiting the Milky Way galaxy, at distances of about 160 000 and 200 000 light-years respectively.

On the far left of the panorama, just left of the foreground antennas, is the elongated smudge of the Andromeda galaxy. This galaxy, more than ten times further away than the Magellanic Clouds, is our closest major neighbouring galaxy. It is also the largest galaxy in the Local Group — the group of about 30 galaxies which includes our own — and contains approximately one trillion stars, more than twice as many as the Milky Way. It is the only major galaxy visible with the naked eye. Even though only its most central region is apparent in this image, the galaxy spans the equivalent of six full Moons in the sky.

This photograph was taken by Babak Tafreshi, the latest ESO Photo Ambassador. Babak is also founder of The World At Night, a programme to create and exhibit a collection of stunning photographs and time-lapse videos of the world’s most beautiful and historic sites against a nighttime backdrop of stars, planets and celestial events.

ALMA is being built on the Chajnantor plateau at an altitude of 5000 metres. The observatory, which started Early Science operations on 30 September 2011, will eventually consist of 66 antennas operating together as a single giant telescope. This international astronomy facility is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.



5 December 2011

The VLT’s Next-generation Laser Launch Telescope

This telescope is an important new component of the Four Laser Guide Star Facility, which will sharpen the already excellent vision of ESO’s Very Large Telescope (VLT). Four powerful 20-watt lasers, fired to an altitude of 90 kilometres up in the atmosphere, will help the VLT correct the image distortion caused by turbulence in the air. The Netherlands Organisation for Applied Scientific Research (TNO) is developing the launch telescopes through which the laser beams will be fired. The first of these laser launch telescopes — known as the Optical Tube Assembly — is seen here in the cleanroom at TNO’s Van Leeuwenhoek Laboratory in Delft, the Netherlands, having recently held its Acceptance Review. A special anti-reflective coating gives the lens on the telescope a distinctive blue hue. The photograph was taken by Fred Kamphues, who appears on the left. He is project manager for the Optical Tube Assembly, and is also a new ESO Photo Ambassador. On the right is system engineer Rens Henselmans.

The Four Laser Guide Star Facility is part of the next generation Adaptive Optics Facility, to be installed on the VLT’s 4th Unit Telescope, Yepun, in 2013. Adaptive optics systems rapidly adjust a deformable mirror to counteract the distorting effect of atmospheric turbulence — the same effect that makes stars twinkle — in real time. To do this, they use a guide star as a reference, since the star should appear as a sharp point when the effect of the atmosphere is removed. This lets the telescope make images almost as sharp as if it were in space.

ESO has led the way in adaptive optics systems, having used them for over 20 years on its telescopes. The first such system on the VLT was installed just over ten years ago (see eso0137). In early 2006, the technology was improved with the first use of a laser guide star at the VLT. The unit projects a high-power laser beam into the sky, which excites a layer of sodium atoms at an altitude of 90 kilometres in the atmosphere and makes them glow. This glowing spot acts as an artificial guide star which can be positioned at will in the sky, so astronomers are not restricted to observations close to a sufficiently bright natural guide star (eso0607).

The next generation Four Laser Guide Star Facility will use four such artificial stars, to improve the removal of atmospheric turbulence over a wider field of view. The technology will also serve as a testbed ahead of the construction of the future European Extremely Large Telescope, which will also have multiple laser guide star units.


28 November 2011

A Galaxy Full of Surprises — NGC 3621 is bulgeless but has three central black holes

This image, from ESO’s Very Large Telescope (VLT), shows a truly remarkable galaxy known as NGC 3621. To begin with, it is a pure-disc galaxy. Like other spirals, it has a flat disc permeated by dark lanes of material and with prominent spiral arms where young stars are forming in clusters (the blue dots seen in the image). But while most spiral galaxies have a central bulge — a large group of old stars packed in a compact, spheroidal region — NGC 3621 doesn’t. In this image, it is clear that there is simply a brightening to the centre, but no actual bulge like the one in NGC 6744 (eso1118), for example.

NGC 3621 is also interesting as it is believed to have an active supermassive black hole at its centre that is engulfing matter and producing radiation. This is somewhat unusual because most of these so-called active galactic nuclei exist in galaxies with prominent bulges. In this particular case, the supermassive black hole is thought to have a relatively small mass, of around 20 000 times that of the Sun.

Another interesting feature is that there are also thought to be two smaller black holes, with masses of a few thousand times that of the Sun, near the nucleus of the galaxy. Therefore, NGC 3621 is an extremely interesting object which, despite not having a central bulge, has a system of three black holes in its central region.

This galaxy is located in the constellation of Hydra (The Sea Snake) and can be seen with a moderate-sized telescope. This image, taken using B, V, and I filters with the FORS1 instrument on the powerful VLT, shows striking detail in this odd object and also reveals a multitude of background galaxies. A number of bright foreground stars that belong to our own Milky Way are also visible.

21 November 2011

A Double Green Flash

At sunset, the sky is often painted with an array of oranges, reds and yellows, and even some shades of pink. There are, however, occasions when a green flash appears above the solar disc for a second or so. One such occurrence was captured beautifully in this picture taken from Cerro Paranal, a 2600-metre-high mountain in the Chilean Atacama Desert, by ESO Photo Ambassador Gianluca Lombardi. Cerro Paranal is home to ESO’s Very Large Telescope.

The green flash is a rather rare phenomenon; seeing such a transient event requires an unobstructed view of the setting (or rising) Sun and a very stable atmosphere. At Paranal the atmospheric conditions are just right for this, making the green flash a relatively common sight (see for example eso0812). But a double green flash such as this one is noteworthy even for Paranal.

The green flash occurs because the Earth’s atmosphere works like a giant prism that bends and disperses the sunlight. This effect is particularly significant at sunrise and sunset when the solar rays go through more of the lower, denser layers of the atmosphere. Shorter wavelength blue and green light from the Sun is bent more than longer wavelength orange and red, so it appears slightly higher in the sky than orange or red rays from the point of view of an observer.

When the Sun is close to the horizon and conditions are just right, a mirage effect related to the temperature gradient in the atmosphere can magnify the dispersion — the separation of colours — and produce the elusive green flash. A blue flash is almost never seen as the blue light is scattered by molecules and particles in the dense blanket of air towards the horizon.

The mirage can also distort the shape of the Sun and that of the flash. We see two bands of green light in this image because the weather conditions created two alternating cold and warm layers of air in the atmosphere.

This stunning photo was taken by ESO Photo Ambassador Gianluca Lombardi on 28 March 2011. The phenomenon was captured on camera as the Sun was setting on a sea of clouds below Cerro Paranal.

« Previous 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | ... | 16 Next »
Showing 121 to 140 of 320
Bookmark and Share

Also see our