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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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    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
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    VLT Survey Telescope

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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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    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
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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
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    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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  • richardmitnick 8:16 am on April 15, 2014 Permalink | Reply
    Tags: , , , , ESO VLTI   

    From ESO: “Sharpest views of Betelgeuse reveal how supergiant stars lose mass” 2009 


    European Southern Observatory

    29 July 2009
    Contacts

    Pierre Kervella
    Observatoire de Paris-Meudon
    Paris, France
    Tel: +33 1 45 07 79 66
    Email: Pierre.Kervella@obspm.fr

    Keiichi Ohnaka
    Max-Planck Institute for Radio Astronomy
    Bonn, Germany
    Tel: +33 1 45 07 79 66
    Email: kohnaka@mpifr-bonn.mpg.de

    Olivier Hainaut
    ESO
    Garching, Germany
    Tel: +49 89 3200 6752
    Email: ohainaut@eso.org

    Using different state-of-the-art techniques on ESO’s Very Large Telescope, two independent teams of astronomers have obtained the sharpest ever views of the supergiant star Betelgeuse. They show that the star has a vast plume of gas almost as large as our Solar System and a gigantic bubble boiling on its surface. These discoveries provide important clues to help explain how these mammoths shed material at such a tremendous rate.

    bet

    Betelgeuse — the second brightest star in the constellation of Orion (the Hunter) — is a red supergiant, one of the biggest stars known, and almost 1000 times larger than our Sun. It is also one of the most luminous stars known, emitting more light than 100000 Suns. Such extreme properties foretell the demise of a short-lived stellar king. With an age of only a few million years, Betelgeuse is already nearing the end of its life and is soon doomed to explode as a supernova. When it does, the supernova should be seen easily from Earth, even in broad daylight.

    Red supergiants still hold several unsolved mysteries. One of them is just how these behemoths shed such tremendous quantities of material — about the mass of the Sun — in only 10 000 years. Two teams of astronomers have used ESO’s Very Large Telescope (VLT) and the most advanced technologies to take a closer look at the gigantic star. Their combined work suggests that an answer to the long-open mass-loss question may well be at hand.

    ESO VLT
    VLT

    The first team used the adaptive optics instrument, NACO, combined with a so-called “lucky imaging” technique, to obtain the sharpest ever image of Betelgeuse, even with Earth’s turbulent, image-distorting atmosphere in the way. With lucky imaging, only the very sharpest exposures are chosen and then combined to form an image much sharper than a single, longer exposure would be.

    ESO NACO
    NACO on VLT

    The resulting NACO images almost reach the theoretical limit of sharpness attainable for an 8-metre telescope. The resolution is as fine as 37 milliarcseconds, which is roughly the size of a tennis ball on the International Space Station (ISS), as seen from the ground.

    “Thanks to these outstanding images, we have detected a large plume of gas extending into space from the surface of Betelgeuse,” says Pierre Kervella from the Paris Observatory, who led the team. The plume extends to at least six times the diameter of the star, corresponding to the distance between the Sun and Neptune.

    “This is a clear indication that the whole outer shell of the star is not shedding matter evenly in all directions,” adds Kervella. Two mechanisms could explain this asymmetry. One assumes that the mass loss occurs above the polar caps of the giant star, possibly because of its rotation. The other possibility is that such a plume is generated above large-scale gas motions inside the star, known as convection — similar to the circulation of water heated in a pot.

    To arrive at a solution, astronomers needed to probe the behemoth in still finer detail. To do this Keiichi Ohnaka from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and his colleagues used interferometry. With the AMBER instrument on ESO’s Very Large Telescope Interferometer, which combines the light from three 1.8-metre Auxiliary Telescopes of the VLT, the astronomers obtained observations as sharp as those of a giant, virtual 48-metre telescope. With such superb resolution, the astronomers were able to detect indirectly details four times finer still than the amazing NACO images had already allowed (in other words, the size of a marble on the ISS, as seen from the ground).

    ESO VLT Interferometer

    ESO AMBER
    AMBER

    “Our AMBER observations are the sharpest observations of any kind ever made of Betelgeuse. Moreover, we detected how the gas is moving in different areas of Betelgeuse’s surface ― the first time this has been done for a star other than the Sun”, says Ohnaka.

    The AMBER observations revealed that the gas in Betelgeuse’s atmosphere is moving vigorously up and down, and that these bubbles are as large as the supergiant star itself. Their unrivalled observations have led the astronomers to propose that these large-scale gas motions roiling under Betelgeuse’s red surface are behind the ejection of the massive plume into space.

    This research was presented in two papers to appear in Astronomy and Astrophysics:
    The close circumstellar environment of Betelgeuse: Adaptive optics spectro-imaging in the near-IR with VLT/NACO, by Pierre Kervella et al., and Spatially resolving the inhomogeneous structure of the dynamical atmosphere of Betelgeuse with VLTI/AMBER, by Keiichi Ohnaka et al.

    The teams are composed of P. Kervella, G. Perrin, S. Lacour, and X. Haubois (LESIA, Observatoire de Paris, France), T. Verhoelst (K. U. Leuven, Belgium), S. T. Ridgway (National Optical Astronomy Observatories, USA), and J. Cami (University of Western Ontario, Canada), and of K. Ohnaka, K.-H. Hofmann, T. Driebe, F. Millour, D. Schertl, and G. Weigelt (Max-Planck-Institute for Radio Astronomy, Bonn, Germany), M. Benisty (INAF-Osservatorio Astrofisico di Arcetri, Firenze, Italy), A. Chelli (LAOG, Grenoble, France), R. Petrov and F. Vakili (Lab. H. Fizeau, OCA, Nice, France), and Ph. Stee (Lab. H. Fizeau, OCA, Grasse, France).

    See the full article, with notes, here.

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  • richardmitnick 8:30 am on March 12, 2014 Permalink | Reply
    Tags: , , , , ESO VLTI   

    From ESO: “VLT Spots Largest Yellow Hypergiant Star” 


    European Southern Observatory

    12 March 2014
    Mix of new and old observations reveals exotic binary system

    Contacts

    Olivier Chesneau
    Laboratoire Lagrange / Univ. Nice Sophia-Antipolis, CNRS – Observatoire de la Côte d’Azur
    Nice, France
    Tel: +33 (0)4 92 00 19 79
    Email: olivier.chesneau@oca.eu

    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’s Very Large Telescope Interferometer has revealed the largest yellow star — and one of the ten largest stars found so far. This hypergiant has been found to measure more than 1300 times the diameter of the Sun, and to be part of a double [binary] star system, with the second component so close that it is in contact with the main star. Observations spanning over sixty years, some from amateur observers, also indicate that this rare and remarkable object is changing very rapidly and has been caught during a very brief phase of its life.

    star

    Using ESO’s Very Large Telescope Interferometer (VLTI), Olivier Chesneau (Observatoire de la Côte d’Azur, Nice, France) and an international team of collaborators have found that the yellow hypergiant star HR 5171 A is absolutely huge — 1300 times the diameter of the Sun and much bigger than was expected. This makes it the largest yellow star known. It is also in the top ten of the largest stars known — 50% larger than the famous red supergiant Betelgeuse — and about one million times brighter than the Sun.

    “The new observations also showed that this star has a very close binary partner, which was a real surprise,” says Chesneau. “The two stars are so close that they touch and the whole system resembles a gigantic peanut.”

    The astronomers made use of a technique called interferometry to combine the light collected from multiple individual telescopes, effectively creating a giant telescope up to 140 metres in size. The new results prompted the team to thoroughly investigate older observations of the star spanning more than sixty years, to see how it had behaved in the past.

    Yellow hypergiants are very rare, with only a dozen or so known in our galaxy — the best-known example being Rho Cassiopeiae. They are among the biggest and brightest stars known and are at a stage of their lives when they are unstable and changing rapidly. Due to this instability, yellow hypergiants also expel material outwards, forming a large, extended atmosphere around the star.

    Despite its great distance of nearly 12 000 light-years from Earth, the object can just about be seen with the naked eye by the keen-sighted. HR 5171 A has been found to be getting bigger over the last 40 years, cooling as it grows, and its evolution has now been caught in action. Only a few stars are caught in this very brief phase, where they undergo a dramatic change in temperature as they rapidly evolve.

    By analysing data on the star’s varying brightness, using observations from other observatories, the astronomers confirmed the object to be an eclipsing binary system where the smaller component passes in front and behind the larger one as it orbits. In this case HR 5171 A is orbited by its companion star every 1300 days. The smaller companion is only slightly hotter than HR 5171 A’s surface temperature of 5000 degrees Celsius.

    Chesneau concludes “The companion we have found is very significant as it can have an influence on the fate of HR 5171 A, for example, stripping off its outer layers and modifying its evolution.”

    This new discovery highlights the importance of studying these huge and short-lived yellow hypergiants, and could provide a means of understanding the evolutionary processes of massive stars in general.

    vlti

    See the full article, with notes, here.

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  • richardmitnick 4:07 pm on February 26, 2014 Permalink | Reply
    Tags: , , , , , ESO VLTI   

    From ESO: “Feeding the Monster” 2005 


    European Southern Observatory

    New VLT Images Reveal the Surroundings of a Super-massive Black Hole

    17 October 2005
    Almudena Prieto
    Max-Planck Institute for Astronomy
    Heidelberg, Germany
    Tel: +34 67 702 66 57
    Email: prieto@mpia.de

    Near-infrared images of the active galaxy NGC 1097, obtained with the NACO adaptive optics instrument on ESO’s Very Large Telescope, disclose with unprecedented detail a complex central network of filamentary structure spiralling down to the centre of the galaxy. These observations provide astronomers with new insights on how super-massive black holes lurking inside galaxies get fed.

    centre
    The Centre of the Active Galaxy NGC 1097

    ESO VLT
    VLT

    ESO NACO
    NACO

    Another view of NGC 1097
    ngc
    Credit: ESO, Telescope: UT3/Melipal at VLT, Instrument: VIMOS

    ESO VIMOS
    VIMOS

    “This is possibly the first time that a detailed view of the channelling process of matter, from the main part of the galaxy down to the very end in the nucleus is released,” says Almudena Prieto (Max-Planck Institute, Heidelberg, Germany), lead author of the paper describing these results.

    Located at a distance of about 45 million light-years in the southern constellation Fornax (the Furnace), NGC 1097 is a relatively bright, barred spiral galaxy seen face-on. At magnitude 9.5, and thus just 25 times fainter than the faintest object that can be seen with the unaided eye, it appears in small telescopes as a bright, circular disc.

    NGC 1097 is a very moderate example of an Active Galactic Nucleus (AGN), whose emission is thought to arise from matter (gas and stars) falling into oblivion in a central black hole. However, NGC 1097 possesses a comparatively faint nucleus only, and the black hole in its centre must be on a very strict “diet”: only a small amount of gas and stars is apparently being swallowed by the black hole at any given moment.

    Astronomers have been trying to understand for a long time how the matter is “gulped” down towards the black hole. Watching directly the feeding process requires very high spatial resolution at the centre of galaxies. This can be achieved by means of interferometry as was done with the VLTI MIDI instrument on the central parts of another AGN, NGC 1068, or with adaptive optics.

    ESO VLTI
    ESO VLTI

    ESO VLTI MIDI
    ESO VLTI MIDI

    Thus, astronomers obtained images of NGC 1097 with the adaptive optics NACO instrument attached to Yepun, the fourth Unit Telescope of ESO’s VLT. These new images probe with unprecedented detail the presence and extent of material in the very proximity of the nucleus. The resolution achieved with the images is about 0.15 arcsecond, corresponding to about 30 light-years across. For comparison, this is only 8 times the distance between the Sun and its nearest star, Proxima Centauri.

    As can be seen in last year’s image, NGC 1097 has a very strong bar and a prominent star-forming ring inside it. Interior to the ring, a secondary bar crosses the nucleus almost perpendicular to the primary bar. The newly released NACO near-infrared images show in addition more than 300 star-forming regions, a factor four larger than previously known from Hubble Space Telescope images. These “HII regions” can be seen as white spots in the photo. At the centre of the ring, a moderate active nucleus is located. Details from the nucleus and its immediate surroundings are however outshone by the overwhelming stellar light of the galaxy seen as the bright diffuse emission all over the image.

    The astronomers therefore applied a masking technique that allowed them to suppress the stellar light. This unveils a bright nucleus at the centre, but mostly a complex central network of filamentary structures spiralling down to the centre.

    “Our analysis of the VLT/NACO images of NGC 1097 shows that these filaments end up at the very centre of the galaxy”, says co-author Juha Reunanen from ESO.

    “This network closely resembles those seen in computer models”, adds co-worker Witold Maciejewski from the University of Oxford, UK. “The nuclear filaments revealed in the NACO images are the tracers of cold dust and gas being channelled towards the centre to eventually ignite the AGN.”

    The astronomers also note that the curling of the spiral pattern in the innermost 300 light-years seem indeed to confirm the presence of a super-massive black hole in the centre of NGC 1097. Such a black hole in the centre of a galaxy causes the nuclear spiral to wind up as it approaches the centre, while in its absence the spiral would be unwinding as it moves closer to the centre.

    An image of NGC 1097 and its small companion, NGC 1097A, was taken in December 2004, in the presence of Chilean President Lagos with the VIMOS instrument on ESO’s Very Large Telescope (VLT).

    See the full article with notes, here.

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  • richardmitnick 7:32 am on October 1, 2013 Permalink | Reply
    Tags: , , , , ESO VLTI   

    From ESO: “The star T Leporis as seen with VLTI” 


    European Southern Observatory

    lep
    ESO/J.-B. Le Bouquin et al.
    Release date: 18 February 2009

    This image from ESO’s Very Large Telescope Interferometer is one of the sharpest colour images ever made. It shows the Mira-like star T Leporis in great detail. The central disc is the surface of the star, which is surrounded by a spherical shell of molecular material expelled from the star. In order to appreciate the feat of such measurement, one should realize that the star appears, on the sky, as small as a two-storey house on the Moon. The resolution of the image is about 4 milli-arcseconds.
    In this image, obtained by combining hundreds of interferometric measurements, the blue channel includes infrared light from 1.4 to 1.6 micrometres, the green, from 1.6 to 1.75 micrometres, and the red, from 1.75 to 1.9 micrometres. In the green channel, the molecular envelope is thinner, and appears as a thin ring around the star.

    See the full article here.

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