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  • richardmitnick 8:06 am on February 12, 2018 Permalink | Reply
    Tags: A red giant sheds its skin, , , , , ESO VLTI   

    From ESO: “A red giant sheds its skin” 

    ESO 50 Large

    European Southern Observatory

    1
    ESO/M. Wittkowski (ESO)

    This ghostly image features a distant and pulsating red giant star known as R Sculptoris. Situated 1200 light-years away in the constellation of Sculptor, R Sculptoris is something known as a carbon-rich asymptotic giant branch (AGB) star, meaning that it is nearing the end of its life. At this stage, low- and intermediate-mass stars cool off, create extended atmospheres, and lose a lot of their mass — they are on their way to becoming spectacular planetary nebulae.

    While the basics of this mass-loss process are understood, astronomers are still investigating how it begins near the surface of the star. The amount of mass lost by a star actually has huge implications for its stellar evolution, altering its future, and leading to different types of planetary nebulae. As AGB stars end their lives as planetary nebulae, they produce a vast range of elements — including 50% of elements heavier than iron — which are then released into the Universe and used to make new stars, planets, moons, and eventually the building blocks of life.

    One particularly intriguing feature of R Sculptoris is its dominant bright spot, which looks to be two or three times brighter than the other regions. The astronomers that captured this wonderful image, using ESO’s Very Large TelescopeInterferometer (VLTI), have concluded that R Sculptoris is surrounded by giant “clumps” of stellar dust that are peeling away from the shedding star.

    2009 ESO VLT Interferometer image, Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    This bright spot is, in fact, a region around the star with little to no dust, allowing us to look deeper into the stellar surface.

    This image captures an extremely small section of the sky: approximately 20×20 milliarcseconds. For comparison, Jupiter has an angular size of approximately 40 arcseconds.

    Science paper:
    Aperture synthesis imaging of the carbon AGB star R Sculptoris: Detection of a complex structure and a dominating spot on the stellar disk Astronomy and Astrophysics

    See the full article here .

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    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 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. 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 a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

    ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres

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  • richardmitnick 11:33 am on January 25, 2018 Permalink | Reply
    Tags: , , , , ESO VLTI, Π1 Gruis, This is the Surface of a Giant Star 350 Times Larger Than the Sun,   

    From Universe Today: “This is the Surface of a Giant Star, 350 Times Larger Than the Sun” 

    universe-today

    Universe Today

    24 Jan , 2018
    Matt Williams

    1
    This artist’s impression shows the red supergiant star. Using ESO’s Very Large Telescope Interferometer, an international team of astronomers have constructed the most detailed image ever of this, or any star other than the Sun. Credit: ESO/M. Kornmesser.

    2009 ESO VLT Interferometer image, Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    When it comes to looking beyond our Solar System, astronomers are often forced to theorize about what they don’t know based on what they do. In short, they have to rely on what we have learned studying the Sun and the planets from our own Solar System in order to make educated guesses about how other star systems and their respective bodies formed and evolved.

    For example, astronomers have learned much from our Sun about how convection plays a major role in the life of stars. Until now, they have not been able to conduct detailed studies of the surfaces of other stars because of their distances and obscuring factors. However, in a historic first, an international team of scientists recently created the first detailed images of the surface of a red giant star located roughly 530 light-years away.

    The study recently appeared in the scientific journal Nature under the title Large Granulation cells on the surface of the giant star Π¹ Gruis. The study was led by Claudia Paladini of the Université libre de Bruxelles and included members from the European Southern Observatory, the Université de Nice Sophia-Antipolis, Georgia State University, the Université Grenoble Alpes, Uppsala University, the University of Vienna, and the University of Exeter.

    For the sake of their study, the team used the Precision Integrated-Optics Near-infrared Imaging ExpeRiment (PIONIER) instrument on the ESO’s Very Large Telescope Interferometer (VLTI) to observe the star known as Π¹ Gruis.

    ESO VLTI PIONIER instrument [First light October 2010]

    Located 530 light-years from Earth in the constellation of Grus (The Crane), Π1 Gruis is a cool red giant. While it is the same mass as our Sun, it is 350 times larger and several thousand times as bright.

    See the full article here .

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  • richardmitnick 1:25 pm on December 20, 2017 Permalink | Reply
    Tags: , , , , ESO VLTI, Giant Bubbles on Red Giant Star’s Surface   

    From European Southern Observatory: “Giant Bubbles on Red Giant Star’s Surface” 

    ESO 50 Large

    European Southern Observatory

    20 December 2017
    Claudia Paladini
    ESO
    Santiago, Chile
    Email: cpaladin@eso.org

    Alain Jorissen
    Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles
    Brussels, Belgium
    Tel: +32 (0) 2 6502834
    Email: Alain.Jorissen@ulb.ac.be

    Fabien Baron
    Georgia State University
    Atlanta, Georgia, USA
    Email: fbaron@gsu.edu

    Richard Hook
    ESO Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    1
    Astronomers using ESO’s Very Large Telescope have for the first time directly observed granulation patterns on the surface of a star outside the Solar System — the ageing red giant π1 Gruis. This remarkable new image from the PIONIER instrument reveals the convective cells that make up the surface of this huge star, which has 700 times the diameter of the Sun. Each cell covers more than a quarter of the star’s diameter and measures about 120 million kilometres across. These new results are being published this week in the journal Nature.

    2
    This colourful image shows the sky around the bright pair of stars π1 Gruis (centre-right, very red) and π2 Gruis (centre-left, bluish-white). Just right of centre the bright spiral galaxy IC 5201 is also visible and many other fainter galaxies are scattered across this wide-field image from the Digitized Sky Survey 2. Credit: ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin


    This sequence takes the viewer towards the southern constellation of Grus (The Crane). We zoom in on the pair of stars π1 Gruis (red) and π2 Gruis (bluish-white), and the bright spiral galaxy IC 5201 is also visible. The final shot shows a very detailed view of the surface of the red giant star π1 Gruis from the PIONIER instrument on the VLT Interferometer. Credit: ESO/Digitized Sky Survey 2/N. Risinger (skysurvey.org) Music: Astral Electronic

    Located 530 light-years from Earth in the constellation of Grus (The Crane), π1 Gruis is a cool red giant. It has about the same mass as our Sun, but is 700 times larger and several thousand times as bright [1]. Our Sun will swell to become a similar red giant star in about five billion years.

    An international team of astronomers led by Claudia Paladini (ESO) used the PIONIER instrument on ESO’s Very Large Telescope to observe π1 Gruis in greater detail than ever before.

    ESO VLTI Pionier instrument

    They found that the surface of this red giant has just a few convective cells, or granules, that are each about 120 million kilometres across — about a quarter of the star’s diameter [2]. Just one of these granules would extend from the Sun to beyond Venus. The surfaces — known as photospheres — of many giant stars are obscured by dust, which hinders observations. However, in the case of π1 Gruis, although dust is present far from the star, it does not have a significant effect on the new infrared observations [3].

    When π1 Gruis ran out of hydrogen to burn long ago, this ancient star ceased the first stage of its nuclear fusion programme. It shrank as it ran out of energy, causing it to heat up to over 100 million degrees. These extreme temperatures fueled the star’s next phase as it began to fuse helium into heavier atoms such as carbon and oxygen. This intensely hot core then expelled the star’s outer layers, causing it to balloon to hundreds of times larger than its original size. The star we see today is a variable red giant. Until now, the surface of one of these stars has never before been imaged in detail.

    By comparison, the Sun’s photosphere contains about two million convective cells, with typical diameters of just 1500 kilometres. The vast size differences in the convective cells of these two stars can be explained in part by their varying surface gravities. π1 Gruis is just 1.5 times the mass of the Sun but much larger, resulting in a much lower surface gravity and just a few, extremely large, granules.

    While stars more massive than eight solar masses end their lives in dramatic supernovae explosions, less massive stars like this one gradually expel their outer layers, resulting in beautiful planetary nebulae. Previous studies of π1 Gruis found a shell of material 0.9 light-years away from the central star, thought to have been ejected around 20 000 years ago. This relatively short period in a star’s life lasts just a few tens of thousands of years – compared to the overall lifetime of several billion – and these observations reveal a new method for probing this fleeting red giant phase.

    Notes

    [1] π1 Gruis is named following the Bayer designation system. In 1603 the German astronomer Johann Bayer classified 1564 stars, naming them by a Greek letter followed by the name of their parent constellation. Generally, stars were assigned Greek letters in rough order of how bright they appeared from Earth, with the brightest designated Alpha (α). The brightest star of the Grus constellation is therefore Alpha Gruis.

    π1 Gruis is one of an attractive pair of stars of contrasting colours that appear close together in the sky, the other one naturally being named π2 Gruis. They are bright enough to be well seen in a pair of binoculars. Thomas Brisbane realised in the 1830s that π1 Gruis was itself also a much closer binary star system. Annie Jump Cannon, credited with the creation of the Harvard Classification Scheme, was the first to report the unusual spectrum of π1 Gruis in 1895.

    [2] Granules are patterns of convection currents in the plasma of a star. As plasma heats up at the centre of the star it expands and rises to the surface, then cools at the outer edges, becoming darker and more dense, and descends back to the centre. This process continues for billions of years and plays a major role in many astrophysical processes including energy transport, pulsation, stellar wind and dust clouds on brown dwarfs.

    [3] π1 Gruis is one of the brightest members of the rare S class of stars that was first defined by the American astronomer Paul W. Merrill to group together stars with similarly unusual spectra. π1 Gruis, R Andromedae and R Cygni became prototypes of this type. Their unusual spectra is now known to be the result of the “s-process” or “slow neutron capture process” — responsible for the creation of half the elements heavier than iron.

    The team is composed of C. Paladini (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium; ESO, Santiago, Chile), F. Baron (Georgia State University, Atlanta, Georgia, USA), A. Jorissen (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium), J.-B. Le Bouquin (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), B. Freytag (Uppsala University, Uppsala, Sweden), S. Van Eck (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium), M. Wittkowski (ESO, Garching, Germany), J. Hron (University of Vienna, Vienna, Austria), A. Chiavassa (Laboratoire Lagrange, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, Nice, France), J.-P. Berger (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), C. Siopis (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium), A. Mayer (University of Vienna, Vienna, Austria), G. Sadowski (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium), K. Kravchenko (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium), S. Shetye (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium), F. Kerschbaum (University of Vienna, Vienna, Austria), J. Kluska (University of Exeter, Exeter, UK) and S. Ramstedt (Uppsala University, Uppsala, Sweden).

    See the full article here .

    Please help promote STEM in your local schools.
    STEM Icon

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    Visit ESO in Social Media-

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    ESO Bloc Icon

    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 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. 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 a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

     
  • richardmitnick 6:53 am on August 23, 2017 Permalink | Reply
    Tags: , , , Best Ever Image of a Star’s Surface and Atmosphere, , ESO VLTI, First two-dimensional velocity map of the atmosphere of a star other than the Sun, The red supergiant star Antares   

    From ESO: “Best Ever Image of a Star’s Surface and Atmosphere” 

    ESO 50 Large

    European Southern Observatory

    23 August 2017
    Keiichi Ohnaka
    Instituto de Astronomía — Universidad Católica del Norte
    Antofagasta, Chile
    Tel: +56 55 235 5493
    Email: k1.ohnaka@gmail.com

    Richard Hook
    ESO Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    First map of motion of material on a star other than the Sun.

    1
    Using ESO’s Very Large Telescope Interferometer astronomers have constructed the most detailed image ever of a star — the red supergiant star Antares. They have also made the first map of the velocities of material in the atmosphere of a star other than the Sun, revealing unexpected turbulence in Antares’s huge extended atmosphere. The results were published in the journal Nature.

    3
    Remarkable map of the motions of material on the surface of the red supergiant star Antares. Credit: ESO/K. Ohnaka


    This short ESOcast takes a quick look at this remarkable result. Credit: ESO.
    Directed by: Nico Bartmann.
    Editing: Nico Bartmann.
    Web and technical support: Mathias André and Raquel Yumi Shida.
    Written by: Izumi Hansen and Richard Hook.
    Music: Music written and performed by STAN DART (www.stan-dart.com).
    Footage and photos: ESO, K. Ohnaka, N. Risinger (skysurvey.org), M. Kornmesser, spaceengine.org.
    Executive producer: Lars Lindberg Christensen.

    To the unaided eye the famous, bright star Antares shines with a strong red tint in the heart of the constellation of Scorpius (The Scorpion). It is a huge and comparatively cool red supergiant star in the late stages of its life, on the way to becoming a supernova [1].

    A team of astronomers, led by Keiichi Ohnaka, of the Universidad Católica del Norte in Chile, has now used ESO’s Very Large Telescope Interferometer (VLTI) at the Paranal Observatory in Chile to map Antares’s surface and to measure the motions of the surface material. This is the best image of the surface and atmosphere of any star other than the Sun.

    The VLTI is a unique facility that can combine the light from up to four telescopes, either the 8.2-metre Unit Telescopes, or the smaller Auxiliary Telescopes, to create a virtual telescope equivalent to a single mirror up to 200 metres across. This allows it to resolve fine details far beyond what can be seen with a single telescope alone.

    “How stars like Antares lose mass so quickly in the final phase of their evolution has been a problem for over half a century,” said Keiichi Ohnaka, who is also the lead author of the paper. “The VLTI is the only facility that can directly measure the gas motions in the extended atmosphere of Antares — a crucial step towards clarifying this problem. The next challenge is to identify what’s driving the turbulent motions.”

    Using the new results the team has created the first two-dimensional velocity map of the atmosphere of a star other than the Sun. They did this using the VLTI with three of the Auxiliary Telescopes and an instrument called AMBER to make separate images of the surface of Antares over a small range of infrared wavelengths.

    1
    ESO – VLTI AMBER

    The team then used these data to calculate the difference between the speed of the atmospheric gas at different positions on the star and the average speed over the entire star [2]. This resulted in a map of the relative speed of the atmospheric gas across the entire disc of Antares — the first ever created for a star other than the Sun..

    The astronomers found turbulent, low-density gas much further from the star than predicted, and concluded that the movement could not result from convection [3], that is, from large-scale movement of matter which transfers energy from the core to the outer atmosphere of many stars. They reason that a new, currently unknown, process may be needed to explain these movements in the extended atmospheres of red supergiants like Antares.

    “In the future, this observing technique can be applied to different types of stars to study their surfaces and atmospheres in unprecedented detail. This has been limited to just the Sun up to now,” concludes Ohnaka. “Our work brings stellar astrophysics to a new dimension and opens an entirely new window to observe stars.”

    Notes

    [1] Antares is considered by astronomers to be a typical red supergiant. These huge dying stars are formed with between nine and 40 times the mass of the Sun. When a star becomes a red supergiant, its atmosphere extends outward so it becomes large and luminous, but low-density. Antares now has a mass about 12 times that of the Sun and a diameter about 700 times larger than the Sun’s. It is thought that it started life with a mass more like 15 times that of the Sun, and has shed three solar-masses of material during its life.

    [2] The velocity of material towards or away from Earth can be measured by the Doppler Effect, which shifts spectral lines either towards the red or blue ends of the spectrum, depending on whether the material emitting or absorbing light is receding from or approaching the observer.

    [3] Convection is the process whereby cold material moves downwards and hot material moves upwards in a circular pattern. The process occurs on Earth in the atmosphere and ocean currents, but it also moves gas around within stars.
    More information

    This research was presented in a paper entitled Vigorous atmospheric motion in the red supergiant star Antares, by K. Ohnaka et al., published in the journal Nature.

    The team is composed of K. Ohnaka (Universidad Católica del Norte, Antofagasta, Chile), G. Weigelt (Max- Planck-Institut für Radioastronomie, Bonn, Germany) and K. -H. Hofmann (Max- Planck-Institut für Radioastronomie, Bonn, Germany)

    See the full article here .

    Please help promote STEM in your local schools.
    STEM Icon

    Stem Education Coalition
    Visit ESO in Social Media-

    Facebook

    Twitter

    YouTube

    ESO Bloc Icon

    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 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. 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 a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

     
  • richardmitnick 7:46 am on October 19, 2016 Permalink | Reply
    Tags: , , ESO VLTI, Highest Resolution Image of Eta Carinae   

    From ESO: “Highest Resolution Image of Eta Carinae” 

    ESO 50 Large

    European Southern Observatory

    19 October 2016

    Gerd Weigelt
    Max-Planck-Institut für Radioastronomie
    Bonn, Germany
    Tel: +49 228 525 243
    Email: weigelt@mpifr-bonn.mpg.de

    Dieter Schertl
    Max-Planck-Institut für Radioastronomie
    Bonn, Germany
    Tel: +49 228 525 301
    Email: ds@mpifr-bonn.mpg.de

    Norbert Junkes
    Public Information Officer, Max-Planck-Institut für Radioastronomie
    Bonn, Germany
    Tel: +49 228 525 399
    Email: njunkes@mpifr-bonn.mpg.de

    Mathias Jäger
    Public Information Officer
    Garching bei München, Germany
    Tel: +49 176 62397500
    Email: mjaeger@partner.eso.org

    1
    An international team of astronomers have used the Very Large Telescope Interferometer to image the Eta Carinae star system in the greatest detail ever achieved.

    ESO VLTI image
    ESO VLTI

    They found new and unexpected structures within the binary system, including in the area between the two stars where extremely high velocity stellar winds are colliding. These new insights into this enigmatic star system could lead to a better understanding of the evolution of very massive stars.

    2
    This image represent the best image of the Eta Carinae star system ever made. The observations were made with the Very Large Telescope Interferometer and could lead to a better understanding of the evolution of very massive stars. Credit: ESO

    3
    This image is a colour composite made from exposures from the Digitized Sky Survey 2 (DSS2). The field of view is approximately 4.7 x 4.9 degrees.
    Credit: ESO/Digitized Sky Survey 2. Acknowledgment: Davide De Martin.

    4
    This spectacular panoramic view combines a new image of the field around the Wolf–Rayet star WR 22 in the Carina Nebula (right) with an earlier picture of the region around the unique star Eta Carinae in the heart of the nebula (left). The picture was created from images taken with the Wide Field Imager [WFI] on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile.

    MPG/ESO 2.2 meter telescope at La Silla, Chile
    ESO WFI LaSilla 2.2-m MPG/ESO telescope at La Silla
    MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile; WFI

    5
    This new image of the luminous blue variable Eta Carinae was taken with the NACO near-infrared adaptive optics instrument on ESO’s Very Large Telescope, yielding an incredible amount of detail. The images clearly shows a bipolar structure as well as the jets coming out from the central star. The image was obtained by the Paranal Science team and processed by Yuri Beletsky (ESO) and Hännes Heyer (ESO). It is based on data obtained through broad (J, H, and K; 90 second exposure time per filters) and narrow-bands (1.64, 2.12, and 2.17 microns; probing iron, molecular and atomic hydrogen, respectively; 4 min per filter). Credit: ESO

    Led by Gerd Weigelt from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, a team of astronomers have used the Very Large Telescope Interferometer (VLTI) at ESO’s Paranal Observatory to take a unique image of the Eta Carinae star system in the Carina Nebula.

    This colossal binary system consists of two massive stars orbiting each other and is very active, producing stellar winds which travel at velocities of up to ten million kilometres per hour [1]. The zone between the two stars where the winds from each collide is very turbulent, but until now it could not be studied.

    The power of the Eta Carinae binary pair creates dramatic phenomena. A “Great Eruption” in the system was observed by astronomers in the 1830s. We now know that this was caused by the larger star of the pair expelling huge amounts of gas and dust in a short amount of time, which led to the distinctive lobes, known as the Homunculus Nebula, that we see in the system today. The combined effect of the two stellar winds as they smash into each other at extreme speeds is to create temperatures of millions of degrees and intense deluges of X-ray radiation.

    The central area where the winds collide is so comparatively tiny — a thousand times smaller than the Homunculus Nebula — that telescopes in space and on the ground so far have not been able to image them in detail. The team has now utilised the powerful resolving ability of the VLTI instrument AMBER to peer into this violent realm for the first time. A clever combination — an interferometer — of three of the four Auxiliary Telescopes at the VLT lead to a tenfold increase in resolving power in comparison to a single VLT Unit Telescope. This delivered the sharpest ever image of the system and yielded unexpected results about its internal structures.

    The new VLTI image clearly depict the structure which exists between the two Eta Carinae-stars. An unexpected fan-shaped structure was observed where the raging wind from the smaller, hotter star crashes into the denser wind from the larger of the pair.

    “Our dreams came true, because we can now get extremely sharp images in the infrared. The VLTI provides us with a unique opportunity to improve our physical understanding of Eta Carinae and many other key objects”, says Gerd Weigelt.

    In addition to the imaging, the spectral observations of the collision zone made it possible to measure the velocities of the intense stellar winds [2]. Using these velocities, the team of astronomers were able to produce more accurate computer models of the internal structure of this fascinating stellar system, which will help increase our understanding of how these kind of extremely high mass stars lose mass as they evolve.

    Team member Dieter Schertl (MPIfR) looks forward: “The new VLTI instruments GRAVITY and MATISSE will allow us to get interferometric images with even higher precision and over a wider wavelength range. This wide wavelength range is needed to derive the physical properties of many astronomical objects.”
    Notes

    [1] The two stars are so massive and bright that the radiation they produce rips off their surfaces and spews them into space. This expulsion of stellar material is referred to as stellar “wind”, and it can travel at millions of kilometres per hour.

    [2] Measurements were done through the Doppler effect. Astronomers use the Doppler effect (or shifts) to calculate precisely how fast stars and other astronomical objects move toward or away from Earth. The movement of an object towards or away from us causes a slight shift in its spectral lines. The velocity of the motion can be calculated from this shift.
    More information

    This research was presented in a paper to appear in Astronomy and Astrophysics.

    The team is composed of G. Weigelt (Max Planck Institute for Radio Astronomy, Germany), K.-H. Hofmann (Max Planck Institute for Radio Astronomy, Germany), D. Schertl (Max Planck Institute for Radio Astronomy, Germany), N. Clementel (South African Astronomical Observatory, South Africa) , M.F. Corcoran (Goddard Space Flight Center, USA; Universities Space Research Association, USA), A. Damineli (Universidade de São Paulo, Brazil ), W.-J. de Wit (European Southern Observatory, Chile), R. Grellmann (Universität zu Köln, Germany), J. Groh (The University of Dublin, Ireland ), S. Guieu (European Southern Observatory, Chile), T. Gull (Goddard Space Flight Center, USA), M. Heininger (Max Planck Institute for Radio Astronomy, Germany) , D.J. Hillier (University of Pittsburgh, USA), C.A. Hummel (European Southern Observatory, Germany), S. Kraus (University of Exeter, UK), T. Madura (Goddard Space Flight Center, USA), A. Mehner (European Southern Observatory, Chile), A. Mérand ( European Southern Observatory, Chile), F. Millour (Université de Nice Sophia Antipolis, France), A.F.J. Moffat (Université de Montréal, Canada), K. Ohnaka (Universidad Católica del Norte, Chile), F. Patru (Osservatorio Astrofisico di Arcetri, Italy), R.G. Petrov (Université de Nice Sophia Antipolis, France), S. Rengaswamy (Indian Institute of Astrophysics, India) , N.D. Richardson (The University of Toledo, USA), T. Rivinius (European Southern Observatory, Chile), M. Schöller (European Southern Observatory, Germany), M. Teodoro (Goddard Space Flight Center, USA) , and M. Wittkowski (European Southern Observatory, Germany)

    See the full article here .

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  • richardmitnick 6:16 am on June 23, 2016 Permalink | Reply
    Tags: , , , ESO VLTI   

    From ESO: “Successful First Observations of Galactic Centre with GRAVITY” 

    ESO 50 Large

    European Southern Observatory

    23 June 2016
    Frank Eisenhauer
    GRAVITY Principal Investigator, Max Planck Institute for Extraterrestrial Physics
    Garching, Germany
    Tel: +49 (89) 30 000 3563
    Email: eisenhau@mpe.mpg.de

    Richard Hook
    ESO Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    Hannelore Hämmerle
    Public Information Officer, Max Planck Institute for Extraterrestrial Physics
    Garching, Germany
    Tel: +49 (89) 30 000 3980
    Email: hannelore.haemmerle@mpe.mpg.de

    Black hole probe now working with the four VLT Unit Telescopes

    1

    A European team of astronomers have used the new GRAVITY instrument at ESO’s Very Large Telescope to obtain exciting observations of the centre of the Milky Way by combining light from all four of the 8.2-metre Unit Telescopes for the first time. These results provide a taste of the groundbreaking science that GRAVITY will produce as it probes the extremely strong gravitational fields close to the central supermassive black hole and tests Einstein’s general relativity.

    ESO GRAVITY insrument
    ESO GRAVITY insrument

    The GRAVITY instrument is now operating with the four 8.2-metre Unit Telescopes of ESO’s Very Large Telescope (VLT), and even from early test results it is already clear that it will soon be producing world-class science.

    GRAVITY is part of the VLT Interferometer.

    ESO VLT Interferometer
    ESO VLT Interferometer

    By combining light from the four telescopes it can achieve the same spatial resolution and precision in measuring positions as a telescope of up to 130 metres in diameter. The corresponding gains in resolving power and positional accuracy — a factor of 15 over the individual 8.2-metre VLT Unit Telescopes — will enable GRAVITY to make amazingly accurate measurements of astronomical objects.

    One of GRAVITY’s primary goals is to make detailed observations of the surroundings of the 4 million solar mass black hole at the very centre of the Milky Way [1].

    Sag A*  NASA Chandra X-Ray Observatory 23 July 2014, the supermassive black hole at the center of the Milky Way
    Sag A* NASA Chandra X-Ray Observatory 23 July 2014, the supermassive black hole at the center of the Milky Way

    Although the position and mass of the black hole have been known since 2002, by making precision measurements of the motions of stars orbiting it, GRAVITY will allow astronomers to probe the gravitational field around the black hole in unprecedented detail, providing a unique test of Einstein’s general theory of relativity.

    In this regard, the first observations with GRAVITY are already very exciting. The GRAVITY team [2] has used the instrument to observe a star known as S2 as it orbits the black hole at the centre of our galaxy with a period of only 16 years. These tests have impressively demonstrated GRAVITY’s sensitivity as it was able to see this faint star in just a few minutes of observation.

    The team will soon be able to obtain ultra-precise positions of the orbiting star, equivalent to measuring the position of an object on the Moon with centimetre precision. That will enable them to determine whether the motion around the black hole follows the predictions of Einstein’s general relativity — or not. The new observations show that the Galactic Centre is as ideal a laboratory as one can hope for.

    “It was a fantastic moment for the whole team when the light from the star interfered for the first time — after eight years of hard work,” says GRAVITY’s lead scientist Frank Eisenhauer from the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. “First we actively stabilised the interference on a bright nearby star, and then only a few minutes later we could really see the interference from the faint star — to a lot of high-fives.” At first glance neither the reference star nor the orbiting star have massive companions that would complicate the observations and analysis. “They are ideal probes,” explains Eisenhauer.

    This early indication of success does not come a moment too soon. In 2018 the S2 star will be at its closest to the black hole, just 17 light-hours away from it and travelling at almost 30 million kilometres per hour, or 2.5% of the speed of light. At this distance the effects due to general relativity will be most pronounced and GRAVITY observations will yield their most important results [3]. This opportunity will not be repeated for another 16 years.
    Notes

    [1] The centre of the Milky Way, our home galaxy, lies on the sky in the constellation of Sagittarius (The Archer) and is some 25 000 light-years distant from Earth.

    [2] The GRAVITY consortium consists of: the Max Planck Institutes for Extraterrestrial Physics (MPE) and Astronomy (MPIA), LESIA of Paris Observatory and IPAG of Université Grenoble Alpes/CNRS, the University of Cologne, the Centro Multidisciplinar de Astrofísica Lisbon and Porto (SIM), and ESO.

    [3] The team will, for the first time, be able to measure two relativistic effects for a star orbiting a massive black hole — the gravitational redshift and the precession of the pericentre. The redshift arises because light from the star has to move against the strong gravitational field of the massive black hole in order to escape into the Universe. As it does so it loses energy, which manifests as a redshift of the light. The second effect applies to the star’s orbit and leads to a deviation from a perfect ellipse. The orientation of the ellipse rotates by around half a degree in the orbital plane when the star passes close to the black hole. The same effect has been observed for Mercury’s orbit around the Sun, where it is about 6500 times weaker per orbit than in the extreme vicinity of the black hole. But the larger distance makes it much harder to observe in the Galactic Centre than in the Solar System.

    GRAVITY instrument web page (ESO)
    Orbits of stars around the galactic centre (ESO)

    See the full article here .

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  • richardmitnick 9:21 am on March 9, 2016 Permalink | Reply
    Tags: , , Dusty Disc Around Aging Star, ESO VLTI   

    From ESO: “Sharpest View Ever of Dusty Disc Around Aging Star” 

    ESO 50 Large

    European Southern Observatory

    9 March 2016
    Richard Hook
    ESO Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    ESO VLTI dusty disc around aging star

    The Very Large Telescope Interferometer at ESO’s Paranal Observatory in Chile has obtained the sharpest view ever of the dusty disc around an aging star. For the first time such features can be compared to those around young stars — and they look surprisingly similar. It is even possible that a disc appearing at the end of a star’s life might also create a second generation of planets.

    ESO VLTI image

    As they approach the ends of their lives many stars develop stable discs of gas and dust around them. This material was ejected by stellar winds, whilst the star was passing through the red giant stage of its evolution. These discs resemble those that form planets around young stars. But up to now astronomers have not been able to compare the two types, formed at the beginning and the end of the stellar life cycle.

    Although there are many discs associated with young stars that are sufficiently near to us to be studied in depth, there are no corresponding old stars with discs that are close enough for us to obtain detailed images.

    But this has now changed. A team of astronomers led by Michel Hillen and Hans Van Winckel from the Instituut voor Sterrenkunde in Leuven, Belgium, has used the full power of the Very Large Telescope Interferometer (VLTI) at ESO’s Paranal Observatory in Chile, armed with the PIONIER instrument, and the newly upgraded RAPID detector.

    ESO VLTI Pionier instrument
    Pionier instrument

    ESO RAPID Detector
    RAPID detector

    Their target was the old double star IRAS 08544-4431 [1], lying about 4000 light-years from Earth in the southern constellation of Vela (The Sails). This double star consists of a red giant star, which expelled the material in the surrounding dusty disc, and a less-evolved more normal star orbiting close to it.

    Jacques Kluska, team member from Exeter University, United Kingdom, explains: “By combining light from several telescopes of the Very Large Telescope Interferometer, we obtained an image of stunning sharpness — equivalent to what a telescope with a diameter of 150 metres would see. The resolution is so high that, for comparison, we could determine the size and shape of a one euro coin seen from a distance of two thousand kilometres.”

    Thanks to the unprecedented sharpness of the images [2] from the Very Large Telescope Interferometer, and a new imaging technique that can remove the central stars from the image to reveal what lies around them, the team could dissect all the building blocks of the IRAS 08544-4431 system for the first time.

    The most prominent feature of the image is the clearly resolved ring. The inner edge of the dust ring, seen for the first time in these observations, corresponds very well with the expected start of the dusty disc: closer to the stars, the dust would evaporate in the fierce radiation from the stars.

    “We were also surprised to find a fainter glow that is probably coming from a small accretion disc around the companion star. We knew the star was double, but weren’t expecting to see the companion directly. It is really thanks to the jump in performance now provided by the new detector in PIONIER, that we are able to view the very inner regions of this distant system,” adds lead author Michel Hillen.

    The team finds that discs around old stars are indeed very similar to the planet-forming ones around young stars. Whether a second crop of planets can really form around these old stars is yet to be determined, but it is an intriguing possibility.

    “Our observations and modelling open a new window to study the physics of these discs, as well as stellar evolution in double stars. For the first time the complex interactions between close binary systems and their dusty environments can now be resolved in space and time,” concludes Hans Van Winckel.
    Notes

    [1] The name of the object indicates that it is a source of infrared radiation that was detected and catalogued by the IRAS satellite observatory in the 1980s.

    [2] The resolution of the VLTI, used with the four Auxiliary Telescopes, was about one milliarcsecond (1/1000th of 1/3600th of a degree).
    More information

    This research was presented in a paper entitled Imaging the dust sublimation front of a circumbinary disk, by M. Hillen et al., to appear as a letter in the journal Astronomy & Astrophysics.

    The team is composed of M. Hillen (Instituut voor Sterrenkunde, Leuven, Belgium), J. Kluska (University of Exeter, Exeter, United Kingdom), J.-B. Le Bouquin (UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble, France), H. Van Winckel (Instituut voor Sterrenkunde, Leuven, Belgium), J.-P. Berger (ESO, Garching, Germany), D. Kamath (Instituut voor Sterrenkunde, Leuven, Belgium) and V. Bujarrabal (Observatorio Astronómico Nacional, Alcalá de Henares, Spain).

    See the full article here .

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  • richardmitnick 8:44 am on September 14, 2015 Permalink | Reply
    Tags: , , ESO VLTI,   

    From RAS: “Astronomers peer into the ‘amniotic sac’ of a planet-hosting star” 

    Royal Astronomical Society

    Royal Astronomical Society

    14 September 2015
    Media contact
    Sarah Reed
    University of Leeds
    Tel: +44 (0)113 343 4196
    s.j.reed@leeds.ac.uk

    Science contacts
    Dr Ignacio Mendigutía
    University of Leeds
    Tel: +44(0)113 34 33871
    I.Mendigutia@leeds.ac.uk

    Professor Rene Oudmaijer
    University of Leeds
    Tel: +44 (0)113 34 33886
    roud@ast.leeds.ac.uk

    1
    This image from the NASA/ESA Hubble Space Telescope shows a visible light view of the outer dust around the young star HD 100546. The position of the newly discovered protoplanet is marked with an orange spot. The inner part of this picture is dominated by artifacts from the brilliant central star, which has been digitally subtracted, and the black blobs are not real.
    Date 28 February 2013, 16:00:00
    Source http://www.eso.org/public/images/eso1310d/
    Author ESO/NASA/ESA/Ardila et al.

    NASA Hubble Telescope
    NASA/ESA Hubble

    Astronomers have successfully peered through the ‘amniotic sac’ of a star that is still forming to observe the innermost region of a burgeoning solar system for the first time.

    In a research paper published today in the journal Monthly Notices of the Royal Astronomical Society, an international team of astronomers describe surprising findings in their observations of the parent star, which is called HD 100546.

    Lead author Dr Ignacio Mendigutía, from the School of Physics and Astronomy at the University of Leeds, said: “Nobody has ever been able to probe this close to a star that is still forming and which also has at least one planet so close in.

    “We have been able to detect for the first time emission from the innermost part of the disk of gas that surrounds the central star. Unexpectedly, this emission is similar to that of ‘barren’ young stars that do not show any signs of active planet formation.”

    To observe this distant system, the astronomers used the [ESO] Very Large Telescope Interferometer (VLTI), which is based in an observatory in Chile. The VLTI combines the observing power of four 8.2m-wide telescopes and can make images as sharp as that of a single telescope that is 130m in diameter.

    ESOVLTI
    ESO VLTI MIDI
    ESO VLTI

    Professor Rene Oudmaijer, a co-author of the study, also from the University’s School of Physics and Astronomy, said: “Considering the large distance that separates us from the star (325 light-years), the challenge was similar to trying to observe something the size of a pinhead from 100km away.”

    HD 100546 is a young star (only a thousandth of the age of the Sun) surrounded by a disk-shaped structure of gas and dust, called a ‘proto-planetary disk‘, in which planets can form. Such disks are common around young stars, but the one around HD 100546 is very peculiar: if the star were placed at the centre of our Solar System, the outer part of the disk would extend up to around ten times the orbit of Pluto.

    Dr Mendigutía said: “More interestingly, the disk exhibits a gap that is devoid of material. This gap is very large, about 10 times the size of the space that separates the Sun from the Earth. The inner disk of gas could only survive for a few years before being trapped by the central star, so it must be continuously replenished somehow.

    “We suggest that the gravitational influence of the still-forming planet – or possibly planets – in the gap could be boosting a transfer of material from the gas-rich outer part of the disk to the inner regions.”

    Systems such as HD 100546 which are known to have both a planet and a gap in the proto-planetary disk are extremely rare. The only other example that has been reported is of a system in which the gap in the disk is ten times further out from the parent star than the one in the new study.

    “With our observations of the inner disk of gas in the HD 100546 system, we are beginning to understand the earliest life of planet-hosting stars on a scale that is comparable to our Solar System,” concludes Professor Oudmaijer.

    See the full article here .

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  • richardmitnick 8:49 am on November 3, 2014 Permalink | Reply
    Tags: , , , , ESO VLTI   

    From ESO: “VLTI Detects Exozodiacal Light” 


    European Southern Observatory

    3 November 2014
    Steve Ertel
    European Southern Observatory
    Santiago, Chile
    Email: sertel@eso.org

    Lindsay Marion
    University of Liège
    Liège, Belgium
    Tel: +32 4 366 97 58
    Cell: +32 472 347 742
    Email: lindsay.marion@ulg.ac.be

    Jean-Charles Augereau
    Institut de Planétologie et d’Astrophysique de Grenoble (IPAG)
    Grenoble, France
    Tel: +33 (0)4 76 51 47 86
    Email: Jean-Charles.Augereau@obs.ujf-grenoble.fr

    Richard Hook
    ESO education and Public Outreach Department
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    By using the full power of the Very Large Telescope Interferometer an international team of astronomers has discovered exozodiacal light close to the habitable zones around nine nearby stars. This light is starlight reflected from dust created as the result of collisions between asteroids, and the evaporation of comets. The presence of such large amounts of dust in the inner regions around some stars may pose an obstacle to the direct imaging of Earth-like planets in the future.

    scene

    ESO VLT Interferometer
    ESO VLTI

    Using the Very Large Telescope Interferometer (VLTI) in near-infrared light [1], the team of astronomers observed 92 nearby stars to probe exozodiacal light from hot dust close to their habitable zones and combined the new data with earlier observations [2]. Bright exozodiacal light, created by the glowing grains of hot exozodiacal dust, or the reflection of starlight off these grains, was observed around nine of the targeted stars.

    From dark clear sites on Earth, zodiacal light looks like a faint diffuse white glow seen in the night sky after the end of twilight, or before dawn. It is created by sunlight reflected off tiny particles and appears to extend up from the vicinity of the Sun. This reflected light is not just observed from Earth but can be observed from everywhere in the Solar System.

    The glow being observed in this new study is a much more extreme version of the same phenomenon. While this exozodiacal light — zodiacal light around other star systems — had been previously detected, this is the first large systematic study of this phenomenon around nearby stars.

    In contrast to earlier observations the team did not observe dust that will later form into planets, but dust created in collisions between small planets of a few kilometres in size — objects called planetesimals that are similar to the asteroids and comets of the Solar System. Dust of this kind is also the origin of the zodiacal light in the Solar System.

    “If we want to study the evolution of Earth-like planets close to the habitable zone, we need to observe the zodiacal dust in this region around other stars,” said Steve Ertel, lead author of the paper, from ESO and the University of Grenoble in France. “Detecting and characterising this kind of dust around other stars is a way to study the architecture and evolution of planetary systems.”

    Detecting faint dust close to the dazzling central star requires high resolution observations with high contrast. Interferometry — combining light collected at the exact same time at several different telescopes — performed in infrared light is, so far, the only technique that allows this kind of system to be discovered and studied.

    By using the power of the VLTI and pushing the instrument to its limits in terms of accuracy and efficiency, the team was able to reach a performance level about ten times better than other available instruments in the world.

    For each of the stars the team used the 1.8-metre Auxiliary Telescopes to feed light to the VLTI. Where strong exozodical light was present they were able to fully resolve the extended discs of dust, and separate their faint glow from the dominant light of the star [3].

    ESO Auxiliary telescopes
    ESO 1.8-metre Auxiliary Telescopes

    By analysing the properties of the stars surrounded by a disc of exozodiacal dust, the team found that most of the dust was detected around older stars. This result was very surprising and raises some questions for our understanding of planetary systems. Any known dust production caused by collisions of planetesimals should diminish over time, as the number of planetesimals is reduced as they are destroyed.

    The sample of observed objects also included 14 stars for which the detection of exoplanets has been reported. All of these planets are in the same region of the system as the dust in the systems showing exozodiacal light. The presence of exozodiacal light in systems with planets may create a problem for further astronomical studies of exoplanets.

    Exozodiacal dust emission, even at low levels, makes it significantly harder to detect Earth-like planets with direct imaging. The exozodiacal light detected in this survey is a factor of 1000 times brighter than the zodiacal light seen around the Sun. The number of stars containing zodiacal light at the level of the Solar System is most likely much higher than the numbers found in the survey. These observations are therefore only a first step towards more detailed studies of exozodiacal light.

    “The high detection rate found at this bright level suggests that there must be a significant number of systems containing fainter dust, undetectable in our survey, but still much brighter than the Solar System’s zodiacal dust,” explains Olivier Absil, co-author of the paper, from the University of Liège. “The presence of such dust in so many systems could therefore become an obstacle for future observations, which aim to make direct images of Earth-like exoplanets.”
    Notes

    [1] The team used the VLTI visitor instrument PIONIER, which is able to interferometrically connect all four Auxiliary Telescopes or all four Unit Telescopes of the VLT at the Paranal Observatory. This led to not only extremely high resolution of the targets but also allowed for a high observing efficiency.

    ESO Pionier
    ESO Pionier

    [2] Previous observations were made with the CHARA array — an optical astronomical interferometer operated by the Center for High Angular Resolution Astronomy (CHARA) of the Georgia State University, and its fibred beam combiner FLUOR.

    CHARA Center for High Angular Resolution Array
    CHARA

    [3] As a by-product, these observations have also led to the discovery of new, unexpected stellar companions orbiting around some of the most massive stars in the sample. “These new companions suggest that we should revise our current understanding of how many of this type of star are actually double,” says Lindsay Marion, lead author of an additional paper dedicated to this complementary work using the same data.

    The team is composed of S. Ertel (Université Grenoble Alpes, France; ESO, Chile), O. Absil (University of Liège, Belgium), D. Defrère (University of Arizona, USA), J.-B. Le Bouquin (Université Grenoble Alpes), J.-C. Augereau (Université Grenoble Alpes), L. Marion (University of Liège), N. Blind (Max-Planck Institute for Extraterrestrial Physics, Garching, Germany), A. Bonsor (University of Bristol, United Kingdom), G. Bryden (California Institute of Technology, Pasadena, USA), J. Lebreton (California Institute of Technology), and J. Milli (Université Grenoble Alpes)

    See the full article here.

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  • richardmitnick 7:53 pm on April 18, 2014 Permalink | Reply
    Tags: , , , , , ESO VLTI   

    From ESO: “Double Engine for a Nebula” 2009 


    European Southern Observatory

    5 August 2009
    Contacts

    Florentin Millour
    Max-Planck Institute for Radio Astronomy
    Bonn, Germany
    Tel: +49 228 525 188
    Email: fmillour@mpifr.de

    Henri Boffin
    ESO
    Paranal, Chile
    Tel: +49 89 3200 6222
    Email: hboffin@eso.org

    Valeria Foncea
    ESO
    Chile
    Tel: +56 2 463 3123
    Email: vfoncea@eso.org

    ESO has just [2009] released a stunning new image of a field of stars towards the constellation of Carina (the Keel). This striking view is ablaze with a flurry of stars of all colours and brightnesses, some of which are seen against a backdrop of clouds of dust and gas. One unusual star in the middle, HD 87643, has been extensively studied with several ESO telescopes, including the Very Large Telescope Interferometer (VLTI). Surrounded by a complex, extended nebula that is the result of previous violent ejections, the star has been shown to have a companion. Interactions in this double [binary star] system, surrounded by a dusty disc, may be the engine fuelling the star’s remarkable nebula.

    ds

    ESO VLT Interferometer
    ESO VLTI

    The new image, showing a very rich field of stars towards the Carina arm of the Milky Way, is centred on the star HD 87643, a member of the exotic class of B[e] stars. It is part of a set of observations that provide astronomers with the best ever picture of a B[e] star.

    mw
    Observed structure of the Milky Way’s spiral arms.

    The [above star field] image was obtained with the Wide Field Imager (WFI) attached to the MPG/ESO 2.2-metre telescope at the 2400-metre-high La Silla Observatory in Chile. The image shows beautifully the extended nebula of gas and dust that reflects the light from the star. The central star’s wind appears to have shaped the nebula, leaving bright, ragged tendrils of gas and dust. A careful investigation of these features seems to indicate that there are regular ejections of matter from the star every 15 to 50 years.

    ESO Wide Field Imager 2.2m LaSilla
    WFI on 2.2m telescope

    ESO 2.2 meter telescope
    2.2m telescope at LaSilla

    ESO LaSilla
    ESO at LaSilla

    A team of astronomers, led by Florentin Millour, has studied the star HD 87643 in great detail, using several of ESO’s telescopes. Apart from the WFI, the team also used ESO’s Very Large Telescope (VLT) at Paranal.

    At the VLT, the astronomers used the NACO adaptive optics instrument, allowing them to obtain an image of the star free from the blurring effect of the atmosphere. To probe the object further, the team then obtained an image with the Very Large Telescope Interferometer (VLTI)[above].

    ESO NACO
    NACO on ESO/VLT

    The sheer range of this set of observations, from the panoramic WFI image to the fine detail of the VLTI observations, corresponds to a zoom-in factor of 60 000 between the two extremes. The astronomers found that HD 87643 has a companion located at about 50 times the Earth–Sun distance and is embedded in a compact dust shell. The two stars probably orbit each other in a period between 20 and 50 years. A dusty disc may also be surrounding the two stars.

    The presence of the companion could be an explanation for the regular ejection of matter from the star and the formation of the nebula: as the companion moves on a highly elliptical orbit, it would regularly come very close to HD 87643, triggering an ejection.

    The work on HD 87643 has been published in a paper to appear in Astronomy and Astrophysics: A binary engine fueling HD 87643’s complex circumstellar environment using AMBER/VLTI imaging, by F. Millour et al.

    See the full article, with notes, here.

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