HomeSportsIs something else lurking in the center of the Milky Way?

Is something else lurking in the center of the Milky Way?

Center of the Milky Way

In this illustration, stars are in close orbit around the supermassive black hole lurking at the center of the Milky Way, known as Sagittarius A* (Sgr A*). Credit: Gemini International Observatory/NOIRLab/NSF/AURA/J. da Silva/(Spaceengine), Acknowledgements: M. Zamani (NSF NOIRLab)[2]Accurate glimpses of the supermassive black hole at the heart of the Milky Way

Astronomers are using 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 precise measurements yet of the movements of stars around the supermassive[{” attribute=””>black hole at the center of the

Astronomers have measured the position and speed of four stars in the immediate vicinity of Sagittarius A* (Sgr A*) more precisely than ever before,[1] the supermassive black hole that lurks at the center of the Milky Way. The motions of these stars – called S2, S29, S38 and S55 – have been found to follow trajectories which show that the mass at the center of the Milky Way is almost entirely due to the black hole Sgr A*, leaving very little room for anything. else.

The research team used a variety of state-of-the-art astronomical facilities in this research. To measure star velocities, they used spectroscopy from the Gemini Near Infrared Spectrograph (GNIRS) at Gemini North near the summit of Maunakea in Hawai’i, part of the Gemini International Observatory, a program of NSF’s NOIRLab. and the SINFONI instrument on the European Southern Observatory[{” attribute=””>Très grand télescope. L’instrument GRAVITY du VLTI a été utilisé pour mesurer les positions des étoiles.

Trou noir Sagittaire A

Illustration du trou noir Sagittarius A* au centre de la Voie Lactée. Crédit : Observatoire international Gemini/NOIRLab/NSF/AURA/J. da Silva/(Spaceengine), Remerciements : M. Zamani (NOIRLab de la NSF)

“Nous sommes très reconnaissants à l’Observatoire Gemini, dont l’instrument GNIRS nous a fourni les informations essentielles dont nous avions besoin”, a déclaré Reinhard Genzel, directeur de l’Institut Max Planck pour la physique extraterrestre et co-récipiendaire du prix Nobel de physique 2020. “Cette recherche montre la collaboration mondiale à son meilleur.”

Le centre galactique de la Voie lactée, situé à environ 27 000 années-lumière du Soleil, contient la source radio compacte Sgr A* que les astronomes ont identifiée comme un trou noir supermassif 4,3 millions de fois plus massif que le Soleil. Malgré des décennies d’observations minutieuses – et le prix Nobel décerné pour avoir découvert l’identité de Sgr A *[3] – it has been difficult to prove conclusively that the majority 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 holes, interstellar dust and gas or dark matter.

ESO's VLTI images of stars in the center of the Milky Way

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 Way milky. One of these stars, named S29, was observed as it came closest to the black hole at 13 billion kilometers, or just 90 times the distance between the Sun and Earth. Another star, named S300, has been detected for the first time in new VLTI observations reported by ESO.
Using Gemini North from the international Gemini Observatory, a program of NSF’s NOIRLab and ESO’s VLT, astronomers have measured the position and velocity of these S29 and S55 stars (as well as stars S2 and S38), and found them to 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 easiest way to answer this question is to closely follow the orbits of stars passing close to Sgr A*.”

Einstein’s theory of general 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 an elegant rosette shape – an effect known as Schwarzschild precession. To actually 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 magnitude of precession of these stars allowed them to infer the mass distribution within Sgr A*. They found that any extended mass in the orbit of 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

“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.”


Zoom into the heart of the Milky Way to see the stars observed by the European Southern Observatory’s Very Large Telescope (the last observation was in 2019). Zooming in further reveals stars even closer to the black hole, observed with the GRAVITY instrument on ESO’s Very Large Telescope interferometry in mid-2021.

“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 manager at the National Science Foundation. “Developing instruments over the next decade for widespread use will maintain NOIRLab’s leadership in characterizing the universe around us.”

For more on this research, see Watch Stars Race Around the Milky Way’s Supermassive Black Hole.

Remarks

  1. Sagittarius A* is pronounced as “Sagittarius A star”.
  2. ESO’s VLT is made up of four individual, collocated 8.2-meter 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 night sky objects with[{” attribute=””>accuracy — equivalent to picking out a quarter-dollar coin on the surface of the Moon.
  3. 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

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