Milky Way Shines over Snowy La Silla

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In the outskirts of the Atacama Desert, far from the light-polluted cities of northern Chile, the skies are pitch-black after sunset. Such dark skies allow some of the best astronomical observing to take place — and at an altitude of 2400 metres, ESO’s La Silla Observatory has an incredibly clear view of the night sky. However, even such a remote, high, and dry location cannot always escape the weather that sometimes comes with the winter months, when blankets of snow can cover the mountain peak and its telescope domes.

This image shows a wintry La Silla sitting beneath a spray of stars from our Milky Way, the plane of which slants across the frame. Visible (from right to left) are the ESO 3.6-metre telescope, the 3.58-metre New Technology Telescope (NTT), the ESO 1-metre Schmidt telescope, and the MPG/ESO 2.2-metre telescope, which has snow on its dome. The small dome of the decommissioned Coudé Auxiliary Telescope can be seen adjacent to that of the ESO 3.6-metre telescope, and between it and the NTT are the water tanks of the observatory.

While the sight of snow at La Silla may initially be surprising, the high altitude ESO sites can experience both hot and cold temperatures through the year, and occasionally be subject to harsh conditions.

This photograph was taken by José Francisco Salgado, an ESO Photo Ambassador.

Source: eso.org

Lore on the Move

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In this photograph one of the two ALMA transporters, Lore, is carrying one of the 7-metre-diameter antennas of ALMA, the Atacama Large Millimeter/submillimeter Array. Lore and her twin, Otto, are two bright yellow 28-wheeled vehicles, custom-built to move ALMA’s antennas around on the Chajnantor Plateau at an elevation of 5000 metres. By doing this, they can reconfigure the telescope array to make the most useful observations of a given target. They also move antennas between Chajnantor and the lower altitude Operations Support Facility for maintenance.

ALMA has a main array of fifty 12-metre-diameter antennas, and an additional array of twelve 7-metre antennas and four 12-metre antennas, known as the Atacama Compact Array (ACA). Lore is carrying one of the smaller, 7-metre antennas of the ACA. The 12-metre antennas of the main array cannot be placed closer than 15 metres apart as they would otherwise bump into each other. This minimum separation between antennas limits the maximum scale of the features that they can detect in the sky. This means that the main array cannot observe the broadest features of extended objects such as giant clouds of molecular gas in the Milky Way, or nearby galaxies. The ACA is specifically designed to help ALMA make better observations of these extended objects. Its smaller 7-metre antennas can be placed closer together, making them better able to measure the broader structures that the main array misses.

The dramatic icy spikes in the foreground are known as penitentes (Spanish for penitents). These are a curious natural phenomenon found in high altitude regions, typically more than 4000 metres above sea level. They are thin blades of hardened snow or ice which point towards the Sun, attaining heights from a few centimetres up to several metres.

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.

Links

Source: eso.org

“A drop of ink on the luminous sky”

Wide Field Imager snaps cosmic gecko

13 February 2013

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This image from the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile, shows the bright star cluster NGC 6520 and its neighbour, the strange gecko-shaped dark cloud Barnard 86. This cosmic pair is set against millions of glowing stars from the brightest part of the Milky Way — a region so dense with stars that barely any dark sky is seen across the picture.

This part of the constellation of Sagittarius (The Archer) is one of the richest star fields in the whole sky — the Large Sagittarius Star Cloud. The huge number of stars that light up this region dramatically emphasise the blackness of dark clouds like Barnard 86, which appears at the centre of this new picture from the Wide Field Imager, an instrument mounted on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile.

This object, a small, isolated dark nebula known as a Bok globule [1], was described as “a drop of ink on the luminous sky” by its discoverer Edward Emerson Barnard [2], an American astronomer who discovered and photographed numerous comets, dark nebulae, one of Jupiter’s moons, and made many other contributions. An exceptional visual observer and keen astrophotographer, Barnard was the first to use long-exposure photography to explore dark nebulae.

Through a small telescope Barnard 86 looks like a dearth of stars, or a window onto a patch of distant, clearer sky. However, this object is actually in the foreground of the star field — a cold, dark, dense cloud made up of small dust grains that block starlight and make the region appear opaque. It is thought to have formed from the remnants of a molecular cloud that collapsed to form the nearby star cluster NGC 6520, seen just to the left of Barnard 86 in this image.

NGC 6520 is an open star cluster that contains many hot stars that glow bright blue-white, a telltale sign of their youth. Open clusters usually contain a few thousand stars that all formed at the same time, giving them all the same age. Such clusters usually only live comparatively short lives, on the order of several hundred million years, before drifting apart.

The incredible number of stars in this area of the sky muddles observations of this cluster, making it difficult to learn much about it. NGC 6520’s age is thought to be around 150 million years, and both this star cluster and its dusty neighbour are thought to lie at a distance of around 6000 light-years from our Sun.

The stars that appear to be within Barnard 86 in the image above are in fact in front of it, lying between us and the dark cloud. Although it is not certain whether this is still happening within Barnard 86, many dark nebulae are known to have new stars forming in their centres — as seen in the famous Horsehead Nebula (eso0202), the striking object Lupus 3 (eso1303) and to a lesser extent in another of Barnard’s discoveries, the Pipe Nebula (eso1233). However, the light from the youngest stars is blocked by the surrounding dusty regions, and they can only be seen in infrared or longer-wavelength light.

Notes

[1] Bok globules were first observed in the 1940s by astronomer Bart Bok. They are very cold, dark clouds of gas and dust that often have new stars forming at their centres. These globules are rich in dust that scatters and absorbs background light, so they are almost opaque to visible light.

[2] This quotation comes from E. E. Barnard, Dark Regions in the Sky Suggesting an Obscuration of Light, Yerkes Observatory, Nov 15 1913 (available online here).

More information

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

Contacts

Richard Hook
ESO, La Silla, Paranal, E-ELT and Survey Telescopes Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

Source: eso.org

Laser and Light Painting

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On a clear night in Bavaria, ESO staff attended the filming of an ESOcast episode focusing on ESO’s new compact laser guide star unit, seen here in action at the Allgäu Public Observatory in Ottobeuren, Germany. Using the glow from their mobile phones, staff took advantage of the long-exposure photograph to draw the letters “ESO” in light, while standing in front of the observatory. Just left of the vertical laser beam, the Milky Way can be seen. Just above the horizon over the observatory, the dotted tracks of aircraft can be seen in the distance. The laser has a powerful beam of 20 watts, and to protect pilots and passengers a no-fly zone around the observatory was created by the Deutsche Flugsicherung (responsible for air traffic control in Germany) during the nighttime observing hours.

Laser guide stars are artificial stars created in the Earth’s atmosphere using a laser beam. The laser makes the sodium atoms in a layer 90 kilometres up in the atmosphere glow and so creates an artificial star in the sky that can be observed by a telescope. Using measurements of the artificial star, adaptive optics instruments can then correct the blurring effect of the atmosphere in the observations.

ESO’s innovative concept uses a powerful laser whose beam is launched with a small telescope, combined into a single modular unit which can be mounted directly on a large telescope. The concept, which has been patented and licensed by ESO, will be used to provide the Very Large Telescope (VLT) with four similar laser units. It will also play a key role in the units that will equip the future European Extremely Large Telescope (E-ELT).

At the time of filming, the unit was undergoing testing before being shipped to the ESO Paranal Observatory in Chile, home of the VLT.

Links

Credit:

ESO/M. Kornmesser

The Wings of the Seagull Nebula

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This new image from ESO shows a section of a cloud of dust and glowing gas called the Seagull Nebula. These wispy red clouds form part of the “wings” of the celestial bird and this picture reveals an intriguing mix of dark and glowing red clouds, weaving between bright stars. This new view was captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile.

Running along the border between the constellations of Canis Major (The Great Dog) and Monoceros (The Unicorn) in the southern sky, the Seagull Nebula is a huge cloud mostly made of hydrogen gas. It’s an example of what astronomers refer to as an HII region. Hot new stars form within these clouds and their intense ultraviolet radiation causes the surrounding gas to glow brightly.

The reddish hue in this image is a telltale sign of the presence of ionised hydrogen [1]. The Seagull Nebula, known more formally as IC 2177, is a complex object with a bird-like shape that is made up of three large clouds of gas — Sharpless 2-292 (eso1237) forms the “head”, this new image shows part of Sharpless 2-296, which comprises the large “wings”, and Sharpless 2-297 is a small, knotty addition to the tip of the gull’s right “wing” [2].

These objects are all entries in the Sharpless nebula catalogue, a list of over 300 glowing clouds of gas compiled by American astronomer Stewart Sharpless in the 1950s. Before he published this catalogue Sharpless was a graduate student at the Yerkes Observatory near Chicago, USA, where he and his colleagues published observational work that helped to show that the Milky Way is a spiral galaxy with vast, curved arms.

Spiral galaxies can contain thousands of HII regions, almost all of which are concentrated along their spiral arms. The Seagull Nebula lies in one of the spiral arms of the Milky Way. But this is not the case for all galaxies; while irregular galaxies do contain HII regions, these are jumbled up throughout the galaxy, and elliptical galaxies are different yet again — appearing to lack these regions altogether. The presence of HII regions indicates that active star formation is still in progress in a galaxy.

This image of Sharpless 2-296 was captured by the Wide Field Imager (WFI), a large camera mounted on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. It shows only a small section of the nebula, a large cloud that is furiously forming hot stars in its interior. The frame shows Sharpless 2-296 lit up by several particularly bright young stars — there are many other stars scattered across the region, including one so bright that stands out as the gull’s “eye” in pictures of the entire complex.

Wide-field images of this region of the sky show a multitude of interesting astronomical objects. The young bright stars within the nebula are part of the nearby star-forming region of CMa R1 in the constellation of Canis Major, which is filled with bright stars and clusters. Also lying close to the Seagull Nebula is the Thor’s Helmet Nebula, an object that was imaged using ESO’s Very Large Telescope (VLT) on ESO’s 50th Anniversary, 5 October 2012, with the help of Brigitte Bailleul — winner of the Tweet Your Way to the VLT! competition (eso1238a).

Notes

[1] Astronomers use the term HII to mean ionised hydrogen and HI for atomic hydrogen. A hydrogen atom consists of an electron bound to a proton but in an ionised gas atoms are split into freely moving electrons and positive ions, in this case just single protons.

[2] These objects are officially designated Sh 2-292, Sh 2-296, and Sh 2-297 respectively in the SIMBAD astronomical database.

More information

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

Contacts

Richard Hook
ESO, La Silla, Paranal, E-ELT & Survey Telescopes Press Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

Source: eso.org

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