Picture of the Week

15 November 2010

An Ancient Cluster of Stars Against a Stunning Background

Among the myriad of stars in this image shines NGC 2257, a collection of cosmic gems bound tightly by gravity. Many billions of years old, but still sparkling brightly, it is an eye-catching astronomical object.

NGC 2257 is a globular cluster, the name given to the roughly spherical concentrations of stars that orbit galactic cores, but are often found far out from the centres in the halo areas of galaxies. Globular clusters contain very old stars, being typically over 10 billion years old, and can therefore be used like a "fossil record" to learn more about the Universe’s past. They are densely packed, with tens to hundreds of thousands of stars gathered within a diameter of just a few tens of light-years. NGC 2257 lies on the outskirts of the Large Magellanic Cloud (LMC), a satellite galaxy of our own Milky Way. It is one of 15 very old globular clusters in the LMC.

The image is made from data taken with the Wide Field Imager instrument on the 2.2-metre MPG/ESO telescope at La Silla, in B, V and I filters, which are shown here in blue, green and red respectively. The field of view is approximately 20 by 20 arcminutes. These observations were made as part of the ESO Imaging Survey project, which was planned to make public imaging surveys to identify targets for follow-up observations with the Very Large Telescope.

Links


8 November 2010

Shooting a Laser at the Galactic Centre

This impressive image, taken on 10 May 2010 by ESO astronomer Yuri Beletsky, beautifully depicts the sky above Paranal. One of the 8.2-metre telescopes of ESO's Very Large Telescope, Yepun, Unit Telescope 4, is seen against the wonderful backdrop of the myriad of stars and dust that makes up the Milky Way. A laser beam is coming out of Yepun, aiming perfectly at the Galactic Centre. When used with the adaptive optics system the artificial star created by the beam allows the telescope to obtain images and spectra that are free from the blurring effect of the atmosphere. When this image was taken, astronomers Stefan Gillessen and Hauke Enkel were using the SINFONI instrument, together with the laser guide star facility, to study the centre of our Milky Way, where a supermassive black hole is lurking.

The field of view of the image is very wide, about 180 degrees. One of the 1.8-metre Auxiliary Telescopes used for interferometry can be seen on the right.


1 November 2010

ESO’s Very Large Telescope Peers into a Distant Nebula*

Astronomers using data from ESO's Very Large Telescope (VLT), at the Paranal Observatory in Chile, have made an impressive composite of the nebula Messier 17, also known as the Omega Nebula or the Swan Nebula. The painting-like image shows vast clouds of gas and dust illuminated by the intense radiation from young stars.

The image shows a central region about 15 light-years across, although the entire nebula is even larger, about 40 light-years in total. Messier 17 is in the constellation of Sagittarius (the Archer), about 6000 light-years from Earth. It is a popular target for amateur astronomers, who can obtain good quality images using small telescopes.

These deep VLT observations were made at near-infrared wavelengths with the ISAAC instrument. The filters used were J (1.25 µm, shown in blue), H (1.6 µm, shown in green), and K (2.2 µm, shown in red). In the centre of the image is a cluster of massive young stars whose intense radiation makes the surrounding hydrogen gas glow. To the lower right of the cluster is a huge cloud of molecular gas. At visible wavelengths, dust grains in the cloud obscure our view, but by observing in infrared light, the glow of the hydrogen gas behind the cloud can be seen shining faintly through. Hidden in this region, which has a dark reddish appearance, the astronomers found the opaque silhouette of a disc of gas and dust. Although it is small in this image, the disc has a diameter of about 20 000 AU, dwarfing our Solar System (1 AU is the distance between the Earth and the Sun). It is thought that this disc is rotating and feeding material onto a central protostar — an early stage in the formation of a new star.

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

Links

  • The research for which these observations were originally made was described in ESO press release eso0416.

25 October 2010

Starry La Silla

The stars rotate around the southern celestial pole during a night at ESO’s La Silla Observatory in northern Chile. The fuzzy parts in the trails on the right are due to the Magellanic Clouds, two small galaxies neighbouring the Milky Way. The dome seen in the image hosts ESO’s 3.6-metre telescope and is home to HARPS (High Accuracy Radial velocity Planet Searcher), the world’s foremost exoplanet hunter. The rectangular building seen in the lower right of the image contains the 0.25-metre TAROT telescope, designed to react very quickly when a gamma-ray burst is detected. Other telescopes at La Silla include the 2.2-metre MPG/ESO telescope, and the 3.58-metre New Technology Telescope, the first telescope to use active optics and, as such, the precursor to all modern large telescopes. La Silla was ESO’s first observing site and is still one of the premier observatories in the southern hemisphere.

#L


18 October 2010

Reflecting on the VLT

The Sun sets at ESO’s Very Large Telescope (VLT) in this image. Taken at the observatory on Cerro Paranal in the dry Atacama Desert of Chile, the observatory’s four 8.2-metre telescopes can be seen preparing for the night ahead. Three of the VLT’s four Auxiliary 1.8-metre Telescopes (AT), used for interferometry, are also visible. The telescopes are seen reflected in the protection cover of one of the AT stations. The ATs are mounted on tracks and can be moved between precisely defined observing positions from where the beams of collected light are combined in the interferometric laboratory. The ATs are very unusual telescopes, as they are self-contained in their own ultra-compact protective domes, and travel with their own electronics, ventilation, hydraulics and cooling systems. Each AT has a transporter that lifts the telescope and moves it from one position to the other. At 2600 metres above sea level, the observing climate is excellent, with little disturbance from clouds. 


11 October 2010

New Temporary Offices at ESO Headquarters

ESO has grown significantly since 1980, when its European staff originally moved from offices at CERN to a dedicated headquarters building in Garching, near Munich, Germany. In the intervening three decades the number of ESO’s member states has increased from six to fourteen, and the organisation has achieved milestones such as the First Light of the New Technology Telescope at La Silla and of the Very Large Telescope at Paranal, becoming in the process the most productive observatory in the world. Today, ESO is constructing the Atacama Large Millimeter/submillimeter Array at Chajnantor in collaboration with international partners, and is in the detailed design phase of a 40-metre-class European Extremely Large Telescope, which will be “the world’s biggest eye on the sky”.

Over the years, the number of ESO staff working in Garching has increased from about 100 to about 450, as the organisation has grown and tackled these exciting new projects. When the capacity of the headquarters building was exceeded, it became necessary to rent additional office space elsewhere on the Garching Forschungszentrum research campus. A recent development during the summer of 2010 is the construction of several new temporary office buildings, seen on the left in this photograph, which are immediately adjacent to the main headquarters (on the right). These buildings make it possible to bring more of the ESO Garching staff onto the main headquarters site from their scattered offices around the campus, so that people can work more easily together. It is planned that a new permanent building, next to the original headquarters, will be constructed for offices and meeting facilities.


4 October 2010

ALMA Antennas on Chajnantor

Two of the Atacama Large Millimeter/submillimeter Array (ALMA) 12-metre antennas gaze at the sky at the observatory’s Array Operations Site (AOS), high on the Chajnantor plateau at an altitude of 5000 metres in the Chilean Andes.

Eight antennas have been installed at the AOS since November 2009. More antennas will be installed on the Chajnantor plateau during the next months and beyond, allowing astronomers to start producing early scientific results with the ALMA system around late 2011. After this, the interferometer will steadily grow to reach its full scientific potential, with at least 66 antennas.

ALMA is the largest ground-based astronomy project in existence, and will comprise a giant array of 12-metre submillimetre quality antennas, with baselines of up to about 16 kilometres. An additional, compact array of 7-metre and 12-metre antennas will complement the main array. The ALMA project is an international collaboration between Europe, East Asia and North America in cooperation with the Republic of Chile. ESO is the European partner in ALMA.


27 September 2010

A Solargraph taken from APEX at Chajnantor

This unusual and artistic image, made using a technique known as "solargraphy" in which a pinhole camera captures the movement of the Sun in the sky over many months, was taken from the Atacama Pathfinder Experiment (APEX) telescope on the plateau of Chajnantor. The plateau is also where ESO, together with international partners, is building the Atacama Large Millimeter/submillimeter Array (ALMA). The solar trails in the image were recorded over half a year and clearly show the quality of the 5000-metre altitude site, high in the Chilean Andes, for astronomical observations.

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 the cameras, known as "cans". The cans are constructed from small black plastic canisters used for storing 35 mm film cassettes. A pinhole in a sheet of aluminium foil is placed over a small aperture drilled into the side of the can, and a rectangle of black and white photographic printing paper is curled and placed snugly around the inside of the can.

Two cans were sent to APEX where David Rabanus, the APEX Station Manager, mounted one facing west of north on the gatepost of the telescope enclosure, close to the telescope itself, and the other on the roof of the generator powerhouse facing east of north. Both were pointed at an elevation of about 45 degrees. The cans at APEX were exposed for a full six months from mid-December 2009 until the southern winter solstice in June 2010. The image from the second can is shown here. It includes the tilted profile of Cerro Chajnantor on the right, silhouetted against the trails of the rising Sun. The mostly unbroken solar trails show that there were some clouds at the ALMA site during the six months — but not many! This solargraph is so sharp that holes in the fleeting clouds over Chajnantor on the few partly cloudy days sometimes managed to create individual "snapshots" of the solar disc (seen as dots in the broken sequences).

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.

APEX is a collaboration between the Max-Planck Institute for Radio Astronomy (MPIfR), the Onsala Space Observatory (OSO) and ESO. The telescope is operated by ESO.

Links


20 September 2010

Starlight Shines Brightly Above Paranal

After the Sun sets at ESO’s Paranal Observatory darkness descends, but the black sky is speckled with a glorious myriad of sparkling stars. This 15-second exposure demonstrates just how dazzling the skies above Paranal are. Located high in the Atacama Desert in Chile far from any sources of light pollution, on a clear moonless night it is possible to see your shadow cast by the light of the Milky Way alone.

Says visual artist and ESO Photo Ambassador José Francisco Salgado, “The skies at Paranal are among the darkest and steadiest I have photographed. I love photographing observatories and at Paranal it's incredible how you can still see just with starlight and zodiacal light!

In the image the stars of the Milky Way seem to be pouring forth from the open dome of the telescope. The brightest patch close to the telescope is the Carina Nebula (NGC 3372), which contains some of the most massive stars in our galaxy (see for example eso0905 and eso1031). Near the top of the image are the stars of Crux, the Southern Cross. This constellation, and that of Carina, are in the southern sky and are therefore not visible from most northern latitudes.

The telescope in the image is the fourth 1.8-metre Auxiliary Telescope, part of the Very Large Telescope Interferometer (VLTI). The VLTI consists of four 8.2-metre telescopes, and the four smaller Auxiliary Telescopes, which have mirrors 1.8 metres across. Thanks to the size of the telescopes, their cutting-edge technology, and the excellent conditions at the site, it is no wonder that Paranal is considered the most advanced visible-light observatory in the world.


13 September 2010

The Great Barred Spiral Galaxy

Spiralling around, 61 million light-years away in the constellation Fornax (the Furnace), NGC 1365 is enormous. At 200000 light-years across, it is one of the largest galaxies known to astronomers. This, plus the sharply defined bar of old stars across its structure is why it is also known as the Great Barred Spiral Galaxy. Astronomers think that the Milky Way may look very similar to this galaxy, but at half the size. The bright centre of the galaxy is thought to be due to huge amounts of superhot gas ejected from the ring of material circling a central black hole. Young luminous hot stars, born out of the interstellar clouds, give the arms a prominent appearance and a blue colour. The bar and spiral pattern rotates, with one full turn taking about 350 million years.

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.


6 September 2010

A Laser Beam Towards the Milky Way's Centre*

In mid-August 2010 ESO Photo Ambassador Yuri Beletsky snapped this amazing photo at ESO’s Paranal Observatory. A group of astronomers were observing the centre of the Milky Way using the laser guide star facility at Yepun, one of the four Unit Telescopes of the Very Large Telescope (VLT).

Yepun’s laser beam crosses the majestic southern sky and creates an artificial star at an altitude of 90 km high in the Earth's mesosphere. The Laser Guide Star (LGS) is part of the VLT’s adaptive optics system and is used as a reference to correct the blurring effect of the atmosphere on images. The colour of the laser is precisely tuned to energise a layer of sodium atoms found in one of the upper layers of the atmosphere — one can recognise the familiar colour of sodium street lamps in the colour of the laser. This layer of sodium atoms is thought to be a leftover from meteorites entering the Earth’s atmosphere. When excited by the light from the laser, the atoms start glowing, forming a small bright spot that can be used as an artificial reference star for the adaptive optics. Using this technique, astronomers can obtain sharper observations. For example, when looking towards the centre of our Milky Way, researchers can better monitor the galactic core, where a central supermassive black hole, surrounded by closely orbiting stars, is swallowing gas and dust.

The photo, which was chosen as Astronomy Picture of the Day for 6 September 2010 and Wikimedia Picture of the Year 2010, was taken with a wide-angle lens and covers about 180 degrees of the sky.

 

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

 

#L


30 August 2010

Arp 271 — Galaxies Drawn Together*

NGC 5426 and NGC 5427 are two spiral galaxies of similar sizes engaged in a dramatic dance. It is not certain that this interaction will end in a collision and ultimately a merging of the two galaxies, although the galaxies have already been affected. Together known as Arp 271, this dance will last for tens of millions of years, creating new stars as a result of the mutual gravitational attraction between the galaxies, a pull seen in the bridge of stars already connecting the two. Located 90 million light-years away towards the constellation of Virgo (the Virgin), the Arp 271 pair is about 130 000 light-years across. It was originally discovered in 1785 by William Herschel. Quite possibly, our own Milky Way will undergo a similar collision in about five billion years with the neighbouring Andromeda galaxy, which is now located about 2.6 million light-years away from the Milky Way.

This image was taken with the EFOSC instrument, attached to the 3.58-metre New Technology Telescope at ESO's La Silla Observatory in Chile. The data were acquired through three different filters (B, V, and R) for a total exposure time of 4440 seconds. The field of view is about 4 arcminutes.

 


23 August 2010

Starry Night at Paranal*

During a night at ESO’s Very Large Telescope (VLT), the stars seem to rotate around the southern celestial pole. The skies over Paranal provide splendid observing opportunities for the astronomers below. At the observatory on Cerro Paranal in the dry Atacama Desert of Chile, one of the observatory’s four 8.2-metre telescopes can be seen on the right performing its nightly task of looking at the heavens. Two of the four 1.8-metre Auxiliary Telescopes are also seen in the picture. The dry, high environment at 2600 metres above sea level, and the extraordinarily advanced equipment makes observing time at the VLT highly sought after by astronomers around the world. 


16 August 2010

The 2010 Perseids over the VLT

Every year in mid-August the Perseid meteor shower has its peak. Meteors, colloquially known as “shooting stars”, are caused by pieces of cosmic debris entering Earth’s atmosphere at high velocity, leaving a trail of glowing gases. Most of the particles that cause meteors are smaller than a grain of sand and usually disintegrate in the atmosphere, only rarely reaching the Earth’s surface as a meteorite.

The Perseid shower takes place as the Earth moves through the stream of debris left behind by Comet Swift-Tuttle. In 2010 the peak was predicted to take place between 12–13 August 2010. Despite the Perseids being best visible in the northern hemisphere, due to the path of Comet Swift-Tuttle's orbit, the shower was also spotted from the exceptionally dark skies over ESO’s Paranal Observatory in Chile. In order not to miss any meteors in the display, ESO Photo Ambassador Stéphane Guisard set up 3 cameras to take continuous time-lapse pictures on the platform of the Very Large Telescope during the nights of 12–13 and 13–14 August 2010. This handpicked photograph, from the night of 13–14 August, was one of Guisard’s 8000 individual exposures and shows one of the brightest meteors captured. The scene is lit by the reddened light of the setting Moon outside the left of the frame.

Although the comet debris particles are travelling parallel to each other, the meteors appear to radiate from a spot on the sky in the constellation of Perseus (here seen very low on the horizon and partly covered by the VLT enclosures). This effect is due to perspective, as the parallel tracks seem to converge at a distance. The apparent origin in Perseus is what gives the Perseid meteor shower its name.

Around the globe, many thousands of people were out observing the Perseids. Some of them took part in citizen science projects such as Meteorwatch and the annual campaign organised by the International Meteor Organization (IMO). According to the IMO measurements, the 2010 Perseid meteor shower was above normal with a peak activity of over 100 meteors per hour under optimal viewing conditions, but not spectacular. In the coming nights the Perseids will still be visible, but with fewer and fewer meteors night by night.

Links


9 August 2010

Frenzied Star Birth in Haro 11

Haro 11 appears to shine gently amid clouds of gas and dust, but this placid facade belies the monumental rate of star formation occurring in this “starburst” galaxy. By combining data from ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope, astronomers have created a new image of this incredibly bright and distant galaxy. The team of astronomers from Stockholm University, Sweden, and the Geneva Observatory, Switzerland, have identified 200 separate clusters of very young, massive stars. Most of these are less than 10 million years old. Many of the clusters are so bright in infrared light that astronomers suspect that the stars are still emerging from the cloudy cocoons where they were born. The observations have led the astronomers to conclude that Haro 11 is most likely the result of a merger between a galaxy rich in stars and a younger, gas-rich galaxy. Haro 11 is found to produce stars at a frantic rate, converting about 20 solar masses of gas into stars every year.

Haro galaxies, first discovered by the noted astronomer Guillermo Haro in 1956, are defined by unusually intense blue and violet light. Usually this high energy radiation comes from the presence of many newborn stars or an active galactic nucleus. Haro 11 is about 300 million light-years away and is the second closest of such starburst galaxies.

The paper describing this result (“Super star clusters in Haro 11: Properties of a very young starburst and evidence for a near-infrared flux excess”, by A. Adamo et al.) is available at http://adsabs.harvard.edu/doi/10.1111/j.1365-2966.2010.16983.x


2 August 2010

Exoplanet Hunters at La Silla*

In the search for distant worlds, few telescopes have had as much success as ESO's 3.6-metre telescope and the Swiss 1.2-metre Leonhard Euler Telescope, both of which are shown in this image.

The 3.6-metre telescope is home to HARPS (High Accuracy Radial velocity Planet Searcher), a spectrograph with unrivalled precision, and holder of many records in the field of exoplanet research, including the discovery of the least massive exoplanet, as well as of the smallest ever measured. Together with HARPS, the Leonhard Euler Telescope has allowed astronomers to find that six exoplanets from a larger sample of 27 were orbiting in the opposite direction to the rotation of their host star — providing an unexpected and serious challenge to current theories of planet formation.

At 2400 metres above sea level in the southern part of Chile’s Atacama Desert, La Silla was ESO’s first observation site. Along with the 3.6-metre telescope, it also hosts the New Technology Telescope (NTT) and the MPG/ESO 2.2-metre telescope as well as several national and smaller telescopes.


26 July 2010

Arp 22 Stretches Out

NGC 4027, also known as Arp 22, stretches its single extended spiral arm in this face-on image. Located about 75 million light-years away in the constellation of Corvus (the Crow), this barred spiral galaxy is identified as a peculiar galaxy by this extended arm, thought to be the result of a collision with another galaxy millions of years ago — most likely a small galaxy known as NGC 4027A. NGC 4027 is part of the NGC 4038 Group, a group of galaxies that also contains the famous distorted couple known as the Antennae Galaxies (see eso0209 and heic0615).

This image is based on data collected with the ESO Faint Object Spectrograph and Camera (EFOSC) attached to the 3.58-metre New Technology Telescope (NTT) at the ESO La Silla Observatory in Chile. The data were collected through three broadband filters (B, V and R) and two narrowband filters (Hα and doubly ionised oxygen).


19 July 2010

A European ALMA antenna takes a ride on a transporter

A European Atacama Large Millimeter/submillimeter Array (ALMA) antenna takes a ride on Lore, one of the ALMA Transporters, at the 2900-metre altitude Operations Support Facility in the Chilean Andes. This took place on 23 June 2010, and was the first time that European antennas have been lifted with the transporters, a procedure that was fully successful, with both moves completed in a single day.

The first two European antennas for ALMA have been moved to two new outdoor foundation pads in order to perform tests of their dish surface accuracy. In this process, known as holography, the antennas observe the signals from a special transmitter located on a nearby tower. In order to allow parallel assembly of several antennas, two new foundations have recently been built. As the newly built foundations lie between the original positions of the two antennas and the holography tower, the antennas were moved to the new locations.

The European ALMA antennas are provided by ESO, through a contract with the AEM Consortium (Thales Alenia Space, European Industrial Engineering, and MT-Aerospace). The ALMA antenna transporters are also provided by ESO, and manufactured by the company Scheuerle Fahrzeugfabrik GmbH. ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile.

Links


12 July 2010

Partial Solar Eclipse over the VLT

Yesterday 11 July 2010, between 20:15 and 22:51 CEST, the path of a total solar eclipse streaked across the Pacific Ocean touching several small islands including Tuamotu in French Polynesia, Mangaia in the Cook Islands and Chile's Easter Island. The total eclipse brushed the southern mainland of Chile, and was seen as a partial eclipse in the rest of the country. At ESO's Paranal Observatory ESO Photo Ambassador Yuri Beletsky snapped this photo near the mid-point of the eclipse.

On the mainland of Chile, outside the zone of complete darkness, the partial eclipse was visible from ESO's Paranal Observatory. With the naked eye, eclipses are difficult — and dangerous — to watch until they reach totality, as the Sun is so bright. But a filter reduces the glare and here reveals the advancing disk of the Moon as it moves across the face of the Sun. In this photograph, the filter is held by hand between the camera lens and the Sun, and lets us see the definite bite-mark on the left of the Sun. Around it is the dramatic location of Paranal's Very Large Telescope.

In addition to the ESO staff watching the partial eclipse over Paranal, a small group of enthusiastic science photographers from ESO, including members of the ESO education and Public Outreach Department, spent their vacation at Easter Island to witness the total eclipse. Among them was ESO Photo Ambassador Stéphane Guisard.

Links


5 July 2010

Building the E-ELT

This series of artist’s impressions shows some of the main phases in the early stages of construction of the European Extremely Large Telescope (E-ELT), assuming the final go-ahead is given at the end of 2010. The E-ELT is to be built on Cerro Armazones, a 3060-metre high mountain near ESO’s Paranal Observatory in Chile, and is planned to be operational early in the next decade.

With a primary mirror 39 metres across, far larger than any visible light telescope currently in operation, the E-ELT will be “the world’s biggest eye on the sky”. This will give it an unparalleled power to see faint and distant objects in the sky.

The E-ELT will tackle the biggest scientific challenges of our time, and aim for a number of notable firsts, including tracking down Earth-like planets around other stars in the habitable zones where life could exist — one of the Holy Grails of modern observational astronomy. It will also perform “stellar archaeology” in nearby galaxies, as well as 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 new discoveries made with the E-ELT. The E-ELT may, eventually, revolutionise our perception of the Universe, much as Galileo’s telescope did, 400 years ago.

Erecting the E-ELT’s housing is a major engineering feat. Because of the size of the equipment inside, the moveable dome of the building has to be over 80 m high — about the height of the dome of St Paul’s Cathedral in London.

The design for the E-ELT shown here was published in 2010 and is preliminary.

More information about the E-ELT is available in the E-ELT web pages, the E-ELT Press Kit and the E-ELT FAQ.


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