In this illustration, the stars are seen to be in close orbit around the supermassive black hole lurking at the center of the Milky Way, known as Sagittarius A* (Sgr A*). Credit: International Gemini Observatory / NOIRLab / NSF / AURA / J. da Silva / (Spaceengine), Acknowledgment: M. Zamani (NSF’s NOIRLab)[2]Precise information about the supermassive black hole at the heart of the Milky Way
Astronomers use the Gemini Observatory and an international collaboration of telescopes to shed light on Sagittarius A*.
Obtained with the help of the Gemini North telescope, astronomers have made the most accurate measurements yet of the motions of stars around the supermassive.[{” attribute=””>black hole at the center of the Milky Way. These results show that 99.9% of the mass contained at the very center of the galaxy is due to the black hole, and only 0.1% could include stars, smaller black holes, interstellar dust, and gas, or dark matter.
Astronomers have more precisely than ever measured the position and velocity of four stars in the immediate vicinity of Sagittarius A* (Sgr A*),[1] the supermassive black hole that lurks at the center of the Milky Way. The motions of these stars, named S2, S29, S38, and S55, were found to follow paths showing that the mass at the center of the Milky Way is almost entirely due to Sgr A * black hole, leaving very little room for anything else.
The research team used a variety of state-of-the-art astronomical facilities in this investigation. To measure the stars’ velocities, they used spectroscopy from the Gemini Near-Infrared Spectrograph (GNIRS) at Gemini North, near the summit of Maunakea in Hawaii, part of the Gemini International Observatory, a program of NSF’s NOIRLab, and the SINFONI instrument. . about the European Southern Observatory[{” attribute=””>Telescopio muy grande. El instrumento GRAVITY del VLTI se utilizó para medir las posiciones de las estrellas.
Ilustración del agujero negro Sagitario A* en el centro de la Vía Láctea. Crédito: Observatorio Internacional Gemini / NOIRLab / NSF / AURA / J. da Silva / (Spaceengine), Agradecimiento: M. Zamani (NSF’s NOIRLab)
“Estamos muy agradecidos con el Observatorio Gemini, cuyo instrumento GNIRS nos brindó la información crítica que necesitábamos”, dijo Reinhard Genzel, director del Instituto Max Planck de Física Extraterrestre y co-ganador del Premio Nobel de Física 2020. “Esta investigación muestra lo mejor de la colaboración mundial”.
El Centro Galáctico de la Vía Láctea, ubicado aproximadamente a 27.000 años luz del Sol, contiene la fuente de radio compacta Sgr A * que los astrónomos han identificado como un agujero negro supermasivo 4,3 millones de veces más masivo que el Sol. A pesar de décadas de minuciosas observaciones, y del Premio Nobel otorgado por descubrir la identidad de Sgr A *[3] – it has been difficult to show conclusively that most of this mass belongs only to the supermassive black hole and does not also include a large amount of matter such as stars, smaller black holesinterstellar dust and gas, or dark matter.
These annotated images, obtained with the GRAVITY instrument on ESO’s Very Large Telescope Interferometer (VLTI) between March and July 2021, show stars orbiting very close to Sagittarius A*, the supermassive black hole at the heart of the Milky Way. . One of these stars, called S29, was observed when it came closest to the black hole at 13 billion km, just 90 times the distance between the Sun and Earth. Another star, called S300, was detected for the first time in new VLTI observations reported by ESO.
Using Gemini North from the Gemini International Observatory, a program of NSF’s NOIRLab and ESO’s VLT, astronomers have more precisely measured the position and velocity of these stars S29 and S55 (as well as stars S2 and S38) than ever before. and they found that it will move in a way that shows that the mass at the center of the Milky Way is almost entirely due to the Sagittarius A* black hole, leaving very little room for anything else. Credit: ESO/GRAVITY Collaboration
“With the 2020 Nobel Prize in Physics awarded for the confirmation that Sgr A* is indeed a black hole, we now want to go further. We would like to understand if there is something else hidden in the center of the Milky Way, and if general relativity is indeed the correct theory of gravity in this extreme laboratory”, explained Stefan Gillessen, one of the astronomers involved in this work. “The simplest way to answer that question is to keep a close eye on the orbits of stars that pass close to Sgr A*.”
Einstein’s general theory of relativity predicts that the orbits of stars around a supermassive compact object are subtly different from those predicted by classical Newtonian physics. In particular, general relativity predicts that the orbits of stars will trace out an elegant rosette shape, an effect known as Schwarzschild precession. To really see the stars tracing this rosette, the team tracked the position and velocity of four stars in the immediate vicinity of Sgr A*, called S2, S29, S38, and S55. The team’s observations of the precession of these stars allowed them to infer the mass distribution within Sgr A*. They found that any mass extended within the orbit of the star S2 contributes at most the equivalent of 0.1% of the mass of the supermassive black hole.
animated sequence of[{” attribute=””>ESO’s Very Large Telescope Interferometer (VLTI) images of stars around the Milky Way’s central black hole. This animation shows the orbits of the stars S29 and S55 as they move close to Sagittarius A* (center), the supermassive black hole at the heart of the Milky Way. As we follow the stars along in their orbits, we see real images of the region obtained with the GRAVITY instrument on the VLTI in March, May, June and July 2021. In addition to S29 and S55, the images also show two fainter stars, S62 and S300. S300 was detected for the first time in new VLTI observations reported by ESO.
Measuring the minute variations in the orbits of distant stars around our galaxy’s supermassive black hole is incredibly challenging. To make further discoveries, astronomers will have to push the boundaries not only of science but also of engineering. Upcoming extremely large telescopes (ELTs) such as the Giant Magellan Telescope and the Thirty Meter Telescope (both part of the US-ELT Program) will allow astronomers to measure even fainter stars with even greater precision.
“We will improve our sensitivity even further in future, allowing us to track even fainter objects,” concluded Gillessen. “We hope to detect more than we see now, giving us a unique and unambiguous way to measure the rotation of the black hole.”
Zooming into the heart of the Milky Way to see the stars as observed by the European Southern Observatory’s Very Large Telescope (last observed in 2019). Zooming in closer reveals even closer stars to the black hole, observed with the GRAVITY instrument on ESO’s Very Large Telescope Interferometry in mid-2021.
“The Gemini observatories continue to provide new insights into the nature of our galaxy and the massive black hole at its center,” said Martin Still, Gemini Program Officer at the National Science Foundation. “Further instrument development over the next decade aimed at wide use will maintain NOIRLab’s leadership in characterizing the Universe around us.”
For more information on this research, see Watch the stars race around the Milky Way’s supermassive black hole.
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- Sagittarius A* is spoken of as “Sagittarius A star”.
- ESO’s VLT is made up of four individually positioned 8.2-metre telescopes that can combine light through a network of mirrors and underground tunnels using a technique known as interferometry, to form the VLTI. GRAVITY uses this technique to measure the position of objects in the night sky with high[{” attribute=””>accuracy — equivalent to picking out a quarter-dollar coin on the surface of the Moon.
- The 2020 Nobel Prize in Physics was awarded in part to Reinhard Genzel and Andrea Ghez “for the discovery of a supermassive compact object at the center of our galaxy.”
This research is presented in the paper “The mass distribution in the Galactic Centre from interferometric astrometry of multiple stellar orbits” which is published in Astronomy & Astrophysics. A companion paper “Deep Images of the Galactic Center with GRAVITY” has also been published in Astronomy & Astrophysics.
References:
“Mass distribution in the Galactic Center based on interferometric astrometry of multiple stellar orbits” by GRAVITY Collaboration: R. Abuter, N. Aimar, A. Amorim, J. Ball, M. Bauböck, J. P. Berger, H. Bonnet, G. Bourdarot, W. Brandner, V. Cardoso, Y. Clénet, Y. Dallilar, R. Davies, P. T. de Zeeuw, J. Dexter, A. Drescher, F. Eisenhauer, N. M. Förster Schreiber, A. Foschi, P. Garcia, F. Gao, E. Gendron, R. Genzel, S. Gillessen, M. Habibi, X. Haubois, G. Heißel,??, T. Henning, S. Hippler, M. Horrobin, L. Jochum, L. Jocou, A. Kaufer, P. Kervella, S. Lacour, V. Lapeyrère, J.-B. Le Bouquin, P. Léna, D. Lutz, T. Ott, T. Paumard, K. Perraut, G. Perrin, O. Pfuhl, S. Rabien, J. Shangguan, T. Shimizu, S. Scheithauer, J. Stadler, A.W. Stephens, O. Straub, C. Straubmeier, E. Sturm, L. J. Tacconi, K. R. W. Tristram, F. Vincent, S. von Fellenberg, F. Widmann, E. Wieprecht, E. Wiezorrek, J. Woillez, S. Yazici and A. Young, 19 January 2022, Astronomy & Astrophysics.
DOI: 10.1051/0004-6361/202142465
“Deep images of the Galactic center with GRAVITY” by GRAVITY Collaboration: R. Abuter, N. Aimar, A. Amorim, P. Arras, M. Bauböck, J. P. Berger, H. Bonnet, W. Brandner, G. Bourdarot, V. Cardoso, Y. Clénet, R. Davies, P. T. de Zeeuw, J. Dexter, Y. Dallilar, A. Drescher, F. Eisenhauer, T. Enßlin, N. M. Förster Schreiber, P. Garcia, F. Gao, E. Gendron, R. Genzel, S. Gillessen, M. Habibi, X. Haubois, G. Heißel, T. Henning, S. Hippler, M. Horrobin, A. Jiménez-Rosales, L. Jochum, L. Jocou, A. Kaufer, P. Kervella, S. Lacour, V. Lapeyrère, J.-B. Le Bouquin, P. Léna, D. Lutz, F. Mang, M. Nowak, T. Ott, T. Paumard, K. Perraut, G. Perrin, O. Pfuhl, S. Rabien, J. Shangguan, T. Shimizu, S. Scheithauer, J. Stadler, O. Straub, C. Straubmeier, E. Sturm, L. J. Tacconi, K. R. W. Tristram, F. Vincent, S. von Fellenberg, I. Waisberg, F. Widmann, E. Wieprecht, E. Wiezorrek, J. Woillez, S. Yazici, A. Young and G. Zins, 19 January 2022, Astronomy & Astrophysics.
DOI: 10.1051/0004-6361/202142459
More information
The team behind this result is composed of The GRAVITY Collaboration, R. Abuter (European Southern Observatory), A. Amorim (Universidade de Lisboa and CENTRA – Centro de Astrofísica e Gravitação), M. Bauböck (Max Planck Institute for Extraterrestrial Physics and University of Illinois), J. P. Berger (University Grenoble Alpes and European Southern Observatory), H. Bonnet (European Southern Observatory), G. Bourdarot (University Grenoble Alpes and Max Planck Institute for Extraterrestrial Physics), V. Cardoso (CENTRA – Centro de Astrofísica e Gravitação and CERN), Y. Clénet (LESIA, Observatoire de Paris), Y. Dallilar (Max Planck Institute for Extraterrestrial Physics), R. Davies (Max Planck Institute for Extraterrestrial Physics), P. T. de Zeeuw (Leiden University and Max Planck Institute for Extraterrestrial Physics), J. Dexter (University of Colorado, Boulder), A. Drescher (Max Planck Institute for Extraterrestrial Physics), A. Eckart (University of Cologne and Max Planck Institute for Radio Astronomy), F. Eisenhauer (Max Planck Institute for Extraterrestrial Physics), N. M. Förster Schreiber (Max Planck Institute for Extraterrestrial Physics), P. Garcia (Universidade do Porto and CENTRA – Centro de Astrofísica e Gravitação), F. Gao (Universität Hamburg and Max Planck Institute for Extraterrestrial Physics), E. Gendron (LESIA, Observatoire de Paris), R. Genzel (Max Planck Institute for Extraterrestrial Physics and University of California, Berkeley), S. Gillessen (Max Planck Institute for Extraterrestrial Physics), M. Habibi (Max Planck Institute for Extraterrestrial Physics), X. Haubois (European Southern Observatory), G. Heißel (LESIA, Observatoire de Paris), T. Henning (Max Planck Institute for Astronomy), S. Hippler (Max Planck Institute for Astronomy), M. Horrobin (University of Cologne), L. Jochum (European Southern Observatory), L. Jocou (University Grenoble Alpes), A. Kaufer (European Southern Observatory), P. Kervella (LESIA, Observatoire de Paris), S. Lacour (LESIA, Observatoire de Paris), V. Lapeyrère (LESIA, Observatoire de Paris), J.-B. Le Bouquin (University Grenoble Alpes), P. Léna (LESIA, Observatoire de Paris), D. Lutz (Max Planck Institute for Extraterrestrial Physics), T. Ott (Max Planck Institute for Extraterrestrial Physics), T. Paumard (LESIA, Observatoire de Paris), K. Perraut (University Grenoble Alpes), G. Perrin (LESIA, Observatoire de Paris), O. Pfuhl (European Southern Observatory and Max Planck Institute for Extraterrestrial Physics), S. Rabien (Max Planck Institute for Extraterrestrial Physics), G. Rodríguez-Coira (LESIA, Observatoire de Paris), J. Shangguan (Max Planck Institute for Extraterrestrial Physics), T. Shimizu (Max Planck Institute for Extraterrestrial Physics), S. Scheithauer (Max Planck Institute for Astronomy), J. Stadler (Max Planck Institute for Extraterrestrial Physics), O. Straub (Max Planck Institute for Extraterrestrial Physics), C. Straubmeier (University of Cologne), E. Sturm (Max Planck Institute for Extraterrestrial Physics), L. J. Tacconi (Max Planck Institute for Extraterrestrial Physics), K. R. W. Tristram (European Southern Observatory), F. Vincent (LESIA, Observatoire de Paris), S. von Fellenberg (Max Planck Institute for Extraterrestrial Physics), F. Widmann (Max Planck Institute for Extraterrestrial Physics), E. Wieprecht (Max Planck Institute for Extraterrestrial Physics), E. Wiezorrek (Max Planck Institute for Extraterrestrial Physics), J. Woillez (European Southern Observatory), S. Yazici (Max Planck Institute for Extraterrestrial Physics and the University of Cologne), and A. Young (Max Planck Institute for Extraterrestrial Physics).
