Tagged: The star S2 Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 8:30 pm on July 26, 2018 Permalink | Reply
    Tags: , , , , , , , , Reinhard Genzel, The star S2   

    From Max Planck Max Planck Institute for Extraterrestrial Physics: ” ‘The galactic centre offers fantastic opportunities’” 

    From Max Planck Max Planck Institute for Extraterrestrial Physics

    July 26, 2018

    Prof. Dr. Reinhard Genzel
    Max Planck Institute for Extraterrestrial Physics, Garching
    +49 89 30000-3280 genzel@mpe.mpg.de

    Helmut Hornung
    Administrative Headquarters of the Max Planck Society, München
    +49 89 2108-1404 hornung@gv.mpg.de

    It is highly likely that there is a black hole at the centre of the Milky Way. The astronomers working under Reinhard Genzel, Director of the Max Planck Institute for Extraterrestrial Physics in Garching near Munich are making repeated detailed studies of the surrounding area of the gravitational trap. Now, the researchers have succeeded in making a huge achievement in the art of observation: from the motion of a star called S2 around the black hole, which is 26,000 light years away, they have measured an effect predicted by Albert Einstein known as the gravitational redshift. What is so special about this observation?

    Star S2 Keck/UCLA Galactic Center Group

    The astronomer and his tool: Reinhard Genzel, Director at the Max Planck Institute for Extraterrestrial Physics, in front of the Very Large Telescope, which he uses to peer into the heart of the Milky Way.
    © MPE

    ESO VLT at Cerro Paranal in the Atacama Desert, elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo

    You have been studying the surrounding area of the black hole in the centre of the Milky Way for more than 20 years. Were you specifically looking for the gravitational redshift that you have now discovered, or did this happen by accident?

    No, the discovery was by no means accidental. We’ve been systematically looking for this and preparing the experiment for ten years now. We’ve known for a long time that the object in the galactic centre has a very high mass, and that it is highly plausible that it is a black hole. However, there’s a difference between plausibility and physical certainty. That’s why we design all kinds of tests, for which the centre of our Milky Way offers wonderful opportunities. In short: our current measurement of the gravitational redshift is already providing very strong evidence of the existence of the black hole in the galactic centre – and of the general theory of relativity.

    The current observations are taking place on the margins of what is measurable. What instruments did you need in order to achieve your successful result?

    Certainly, measurements like these would not have been possible just a few years ago. At that time, we observed the centre of the Milky Way using a single eight-meter mirror in the Very Large Telescope. Now, we us all four telescopes in the system in Chile at the same time by using interferometry.

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

    In radio astronomy, this procedure, in which the waves of an object overlap and this appears sharper as a result, has already been established for decades, but not in the field of optics. For this reason, the Max Planck Institute for Extraterrestrial Physics headed by Frank Eisenhauer, together with the Max Planck Institute for Astronomy, the European Southern Observatory, the University of Cologne, two French CNRS institutes and institutes in Porto and Lisbon, has developed a highly complex instrument called Gravity.


    Gravity processes the signals of the four individual telescopes and offers a huge improvement in the detail resolution in the infrared range. This means that thanks to Gravity, the Very Large Telescope could in theory provide images of two adjacent two-euro coins on the moon. It’s no exaggeration to say that Gravity has led to a breakthrough in the field of optics in matters relating to interferometry.

    A key role during observation is probably also played by adaptive optics. What’s the reason for this?

    Glistening against the awesome backdrop of the night sky above ESO_s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT.

    Turbulences in the Earth’s atmosphere distort the wavefronts of the stars’ light. In principle, the aim is to compensate the crests and troughs of waves. This is made possible through the use of a mirror in the telescope, which has mechanical tappets attached to its rear side. These so-called actuators deform the surface of this small mirror in the beam path up to a thousand times per second, and in this way eliminate the distortions. In this way, we achieve the theoretical resolution of the telescope – and this is higher by a factor of ten than those that are achieved without correcting the air turbulence.

    You said that the centre of the Milky Way offers wonderful opportunities to finally put the general theory of relativity to the test …

    … and the redshift measured by us is one of these tests. In this regard, it’s important to realise that such a redshift is not just caused by the Doppler effect. We know this from everyday life when for example an ambulance drives past us, and the tone level of the siren increases and decreases. At the same time, this means a displacement of the wavelength into the short- or long-wave range. This also occurs with light waves, where reference is made to blueshift or also redshift. This aside, according to the general theory of relativity, a redshift also occurs in the field of gravity when light moves there and fights against it to a certain degree. This effect also has an impact on the radiation of the S2 star, which approaches the black hole up to a distance of around 14 billion kilometres – which is the equivalent of three times the distance between the planet Neptune and the Sun. On 19 May of this year, S2 again passed the place where the distance was lowest during its orbit. For us, this offered a unique opportunity to measure the gravitational redshift.

    Can you foresee conducting further tests for the general theory of relativity?

    Yes, another test would be the Schwarzschild precession. This sounds complicated, but in fact, it’s simple. According to the general theory of relativity, celestial bodies that move around a central mass do not run on closed trajectories. The point of the greatest approximation, the perihelion, constantly continues to move in space. This can be clearly observed with planet Mercury, the perihelion rotation of which has been known for a long time. Its measured value correlates precisely with Einstein’s prediction. It is likely that a similar effect can be observed in the orbits of stars that move around the central black hole of the Milky Way. Indeed, we are already seeing the first signs of this. In two years’ time, we should then have statistically significant measurements. The best test for the general theory of relativity would otherwise be when a star falls into the black hole in front of our eyes. Unfortunately, statistically speaking, this happens only once every 10,000 years.

    The gravitation effect measured by your group is a wonderful piece of evidence supporting Einstein’s theory of relativity. Is there any doubt at all now about the validity of this theory?

    Yes, certainly! To put it in drastic terms: the physical laws known to us to date only apply to a limited range of parameters. The tiniest and the largest in particular, namely quantum physics and the theory of relativity, do not match each other. And so far, a corresponding quantum theory of gravitation has not yet been developed.

    Interview: Helmut Hornung

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    For their astrophysical research, the MPE scientists measure the radiation of far away objects in different wavelenths areas: from millimetere/sub-millimetre and infared all the way to X-ray and gamma-ray wavelengths. These methods span more than twelve decades of the electromagnetic spectrum.

    The research topics pursued at MPE range from the physics of cosmic plasmas and of stars to the physics and chemistry of interstellar matter, from star formation and nucleosynthesis to extragalactic astrophysics and cosmology. The interaction with observers and experimentalists in the institute not only leads to better consolidated efforts but also helps to identify new, promising research areas early on.

    The structural development of the institute mainly has been directed by the desire to work on cutting-edge experimental, astrophysical topics using instruments developed in-house. This includes individual detectors, spectrometers and cameras but also telescopes and integrated, complete payloads. Therefore the engineering and workshop areas are especially important for the close interlink between scientific and technical aspects.

    The scientific work is done in four major research areas that are supervised by one of the directors:

    Center for Astrochemical Studies (CAS)
    Director: P. Caselli

    High-Energy Astrophysics
    Director: P. Nandra

    Infrared/Submillimeter Astronomy
    Director: R. Genzel

    Optical & Interpretative Astronomy
    Director: R. Bender

    Within these areas scientists lead individual experiments and research projects organised in about 25 project teams.

    The Max Planck Society is Germany’s most successful research organization. Since its establishment in 1948, no fewer than 18 Nobel laureates have emerged from the ranks of its scientists, putting it on a par with the best and most prestigious research institutions worldwide. The more than 15,000 publications each year in internationally renowned scientific journals are proof of the outstanding research work conducted at Max Planck Institutes – and many of those articles are among the most-cited publications in the relevant field.

    What is the basis of this success? The scientific attractiveness of the Max Planck Society is based on its understanding of research: Max Planck Institutes are built up solely around the world’s leading researchers. They themselves define their research subjects and are given the best working conditions, as well as free reign in selecting their staff. This is the core of the Harnack principle, which dates back to Adolph von Harnack, the first president of the Kaiser Wilhelm Society, which was established in 1911. This principle has been successfully applied for nearly one hundred years. The Max Planck Society continues the tradition of its predecessor institution with this structural principle of the person-centered research organization.

    The currently 83 Max Planck Institutes and facilities conduct basic research in the service of the general public in the natural sciences, life sciences, social sciences, and the humanities. Max Planck Institutes focus on research fields that are particularly innovative, or that are especially demanding in terms of funding or time requirements. And their research spectrum is continually evolving: new institutes are established to find answers to seminal, forward-looking scientific questions, while others are closed when, for example, their research field has been widely established at universities. This continuous renewal preserves the scope the Max Planck Society needs to react quickly to pioneering scientific developments.

  • richardmitnick 1:53 pm on August 9, 2017 Permalink | Reply
    Tags: , , , , , , The star S2   

    From ESO: “First Evidence for Relativity Effects in Stars Orbiting Supermassive Black Hole at Centre of Galaxy” 

    ESO 50 Large

    European Southern Observatory

    9 August 2017
    Marzieh Parsa
    I. Physikalisches Institut, Universität zu Köln
    Köln, Germany
    Tel: +49(0)221/470-3495
    Email: parsa@ph1.uni-koeln.de

    Andreas Eckart
    I. Physikalisches Institut, Universität zu Köln
    Köln, Germany
    Tel: +49(0)221/470-3546
    Email: eckart@ph1.uni-koeln.de

    Vladimir Karas
    Astronomical Institute, Academy of Science
    Prague, Czech Republic
    Tel: +420-226 258 420
    Email: vladimir.karas@cuni.cz

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

    A new analysis of data from ESO’s Very Large Telescope and other telescopes [I have asked ESO repeatedly to credit all telscopes used in any project, as they are all supported by public money. They apparently prefer to leave us in the dark.] they reveals for the first time that the orbits of stars around the supermassive black hole at the centre of the Milky Way show the subtle effects predicted by Einstein’s general theory of relativity. The orbit of the star S2 is found to be deviating slightly from the path calculated using classical physics. This tantalising result is a prelude to much more precise measurements and tests of relativity that will be made using the GRAVITY instrument as star S2 passes very close to the black hole in 2018.

    ESO GRAVITY insrument on The VLT

    This artist’s impression shows the orbits of three of the stars very close to the supermassive black hole at the centre of the Milky Way. Analysis of data from ESO’s Very Large Telescope and other telescopes has revealed that the orbits of these stars show the subtle effects predicted by Einstein’s general theory of relativity. The orbit of the star called S2 is found to be deviating slightly from the path calculated using classical physics.
    The position of the supermassive black hole is marked with a white circle with a blue halo. Credit: ESO/M. Parsa/L. Calçada

    The orbit of the star S2 is found to be deviating slightly from the path calculated using classical physics. This tantalising result is a prelude to much more precise measurements and tests of relativity that will be made using the GRAVITY instrument as star S2 passes very close to the black hole in 2018.

    At the centre of the Milky Way, 26 000 light-years from Earth, lies the closest supermassive black hole, which has a mass four million times that of the Sun. This monster is surrounded by a small group of stars orbiting at high speed in the black hole’s very strong gravitational field. It is a perfect environment in which to test gravitational physics, and particularly Einstein’s general theory of relativity.

    A team of German and Czech astronomers have now applied new analysis techniques to the very rich set of existing observations of the stars orbiting the black hole, accumulated using ESO’s Very Large Telescope (VLT) in Chile and others over the last twenty years [1]. They compare the measured star orbits to predictions made using classical Newtonian gravity as well as predictions from general relativity.

    The team found evidence for a small change in the motion of one of the stars, known as S2, that is consistent with the predictions of general relativity [2]. The change due to relativistic effects amounts to only a few percent in the shape of the orbit, as well as only about one sixth of a degree in the orientation of the orbit [3]. This is the first time that a measurement of the strength of the general relativistic effects has been achieved for stars orbiting a supermassive black hole.

    Marzieh Parsa, PhD student at the University of Cologne, Germany and lead author of the paper [The Astropysical Journel], is delighted: “The Galactic Centre really is the best laboratory to study the motion of stars in a relativistic environment. I was amazed how well we could apply the methods we developed with simulated stars to the high-precision data for the innermost high-velocity stars close to the supermassive black hole.”

    The central parts of our Galaxy, the Milky Way, as observed in the near-infrared with the NACO instrument on ESO’s Very Large Telescope. The position of the centre, which harbours the (invisible) black hole known as Sgr A*,with a mass 4 million times that of the Sun, is marked by the orange cross.

    The star S2 will make a close pass around the black hole in 2018 when it will be used as a unique probe of the strong gravity and act as a test of Einstein’s general theory of relativity. Credit: ESO/MPE/S. Gillessen et al.

    The high accuracy of the positional measurements, made possible by the VLT’s near-infrared adaptive optics instruments, was essential for the success of the study [4]. These were vital not only during the star’s close approach to the black hole, but particularly during the time when S2 was further away from the black hole. The latter data allowed an accurate determination of the shape of the orbit and how it is changing under the influence of relativity.

    “During the course of our analysis we realised that to determine relativistic effects for S2 one definitely needs to know the full orbit to very high precision,” comments Andreas Eckart, team leader at the University of Cologne.

    As well as more precise information about the orbit of the star S2, the new analysis also gives the mass of the black hole and its distance from Earth to a higher degree of accuracy [5].

    Co-author Vladimir Karas from the Academy of Sciences in Prague, the Czech Republic, is excited about the future: “It is very reassuring that S2 shows relativistic effects as expected on the basis of its proximity to the extreme mass concentration at the centre of the Milky Way. This opens up an avenue for more theory and experiments in this sector of science.”

    This analysis is a prelude to an exciting period for observations of the Galactic Centre by astronomers around the world. During 2018 the star S2 will make a very close approach to the supermassive black hole. This time the GRAVITY instrument, developed by a large international consortium led by the Max-Planck-Institut für extraterrestrische Physik in Garching, Germany [6], and installed on the VLT Interferometer [7], will be available to help measure the orbit much more precisely than is currently possible. Not only is this expected to reveal the general relativistic effects very clearly, but also it will allow astronomers to look for deviations from general relativity that might reveal new physics.

    [1] Data from the near-infrared NACO camera now at VLT Unit Telescope 1 (Antu) and the near-infrared imaging spectrometer SINFONI at the Unit Telescope 4 (Yepun) were used for this study. Some additional published data obtained at the Keck Observatory were also used.



    Keck Observatory, Maunakea, Hawaii, USA

    [2] S2 is a 15-solar-mass star on an elliptical orbit around the supermassive black hole. It has a period of about 15.6 years and gets as close as 17 light-hours to the black hole — or just 120 times the distance between the Sun and the Earth.

    [3] A similar, but much smaller, effect is seen in the changing orbit of the planet Mercury in the Solar System. That measurement was one of the best early pieces of evidence in the late nineteenth century suggesting that Newton’s view of gravity was not the whole story and that a new approach and new insights were needed to understand gravity in the strong-field case. This ultimately led to Einstein publishing his general theory of relativity, based on curved spacetime, in 1915.

    When the orbits of stars or planets are calculated using general relativity, rather than Newtonian gravity, they evolve differently. Predictions of the small changes to the shape and orientation of orbits with time are different in the two theories and can be compared to measurements to test the validity of general relativity.

    [4] An adaptive optics system compensates for the image distortions produced by the turbulent atmosphere in real time and allows the telescope to be used at much angular resolution (image sharpness), in principle limited only by the mirror diameter and the wavelength of light used for the observations.

    [5] The team finds a black hole mass of 4.2 × 106 times the mass of the Sun, and a distance from us of 8.2 kiloparsecs, corresponding to almost 27 000 light-years.

    [6] The University of Cologne is part of the GRAVITY team (http://www.mpe.mpg.de/ir/gravity) and contributed the beam combiner spectrometers to the system.

    [7] GRAVITY First Light was in early 2016 and it is already observing the Galactic Centre.

    The team is composed of Marzieh Parsa, Andreas Eckart (I.Physikalisches Institut of the University of Cologne, Germany; Max Planck Institute for Radio Astronomy, Bonn, Germany), Banafsheh Shahzamanian (I.Physikalisches Institut of the University of Cologne, Germany), Christian Straubmeier (I.Physikalisches Institut of the University of Cologne, Germany), Vladimir Karas (Astronomical Institute, Academy of Science, Prague, Czech Republic), Michal Zajacek (Max Planck Institute for Radio Astronomy, Bonn, Germany; I.Physikalisches Institut of the University of Cologne, Germany) and J. Anton Zensus (Max Planck Institute for Radio Astronomy, 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-




    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.

    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 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 to be built at Cerro Armazones at 3,060 m.

    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)

    • Jose 3:04 pm on September 20, 2017 Permalink | Reply

      Here you may find a simple post-Newtonian solution for Mercury’s orbit precession
      Gravity is a little big bigger than in Newton’s law; it increases with speed -kinetic energy- where the maximum is the double gravity in the case of light.
      Global Physics also predicts the anomalous precession of Mercury’s orbit as Paul Gerber did 20 years before Einstein. https://molwick.com/en/gravitation/077-mercury-orbit.html


Compose new post
Next post/Next comment
Previous post/Previous comment
Show/Hide comments
Go to top
Go to login
Show/Hide help
shift + esc
%d bloggers like this: