“Sinnsblåsende” varm gassboble oppdaget glidelås rundt Melkeveiens supermassive svarte hull

Varm gassboble som virvler rundt vårt supermassive sorte hull

Astronomer har oppdaget tegn på en “hot spot” i bane rundt Skytten A*, det sorte hullet i sentrum av galaksen vår.

Astronomer har oppdaget tegn på en “hot spot” i bane rundt Skytten A*, den[{” attribute=””>black hole at the center of our galaxy, using the Atacama Large Millimeter/submillimeter Array (ALMA). The finding helps us better understand the enigmatic and dynamic environment of our supermassive black hole.

“We think we’re looking at a hot bubble of gas zipping around Sagittarius A* on an orbit similar in size to that of the planet Mercury, but making a full loop in just around 70 minutes. This requires a mind-blowing velocity of about 30% of the speed of light!” says Maciek Wielgus of the Max Planck Institute for Radio Astronomy in Bonn, Germany. He led the study that was published today (September 22, 2022) in the journal Astronomy & Astrophysics.

The Orbit of the Hot Spot Around Sagittarius A*

This shows a still image of the supermassive black hole Sagittarius A*, as seen by the Event Horizon Collaboration (EHT), with an artist’s illustration indicating where the modeling of the ALMA data predicts the hot spot to be and its orbit around the black hole. Credit: EHT Collaboration, ESO/M. Kornmesser (Acknowledgment: M. Wielgus)

The observations were made with ALMA in the Chilean Andes, during a campaign by the Event Horizon Telescope (EHT) Collaboration to image black holes. ALMA is — a radio telescope co-owned by the European Southern Observatory (ESO). In April 2017 the EHT linked together eight existing radio telescopes worldwide, including ALMA, resulting in the recently released first-ever image of Sagittarius A*. To calibrate the EHT data, Wielgus and his colleagues, who are members of the EHT Collaboration, used ALMA data recorded simultaneously with the EHT observations of Sagittarius A*. To the research team’s surprise, there were more clues to the nature of the black hole hidden in the ALMA-only measurements.


Ved å bruke ALMA har astronomer funnet en varm gassboble som virvler rundt Skytten A*, det sorte hullet i sentrum av galaksen vår, med 30 % av lysets hastighet.

Ved en tilfeldighet ble noen av observasjonene gjort kort tid etter at et utbrudd eller blus av røntgenenergi ble sendt ut fra sentrum av galaksen vår, som ble oppdaget av[{” attribute=””>NASA’s Chandra X-ray Observatory. These kinds of flares, previously observed with X-ray and infrared telescopes, are thought to be associated with so-called ‘hot spots’, hot gas bubbles that orbit very fast and close to the black hole.

“What is really new and interesting is that such flares were so far only clearly present in X-ray and infrared observations of Sagittarius A*. Here we see for the first time a very strong indication that orbiting hot spots are also present in radio observations,” says Wielgus, who is also affiliated with the Nicolaus Copernicus Astronomical Center, in Warsaw, Poland and the Black Hole Initiative at Harvard University, USA.


Denne videoen viser en animasjon av et hot spot, en boble av varm gass, i bane rundt Skytten A*, et svart hull som er fire millioner ganger mer massivt enn vår sol som befinner seg i sentrum av vår[{” attribute=””>Milky Way. While the black hole (center) has been directly imaged with the Event Horizon Telescope, the gas bubble represented around it has not: its orbit and velocity are inferred from both observations and models. The team who discovered evidence for this hot spot — using the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner — predicts the gas bubble orbits very close to the black hole, at a distance about five times larger than the black hole’s boundary or “event horizon.”

The astronomers behind the discovery also predict that the hot spot becomes dimmer and brighter as it goes around the black hole, as indicated in this animation. Additionally, they can infer that it takes 70 minutes for the gas bubble to complete an orbit, putting its velocity at an astonishing 30% of the speed of light.

Credit: EHT Collaboration, ESO/L. Calçada (Acknowledgment: M. Wielgus)

“Perhaps these hot spots detected at infrared wavelengths are a manifestation of the same physical phenomenon: as infrared-emitting hot spots cool down, they become visible at longer wavelengths, like the ones observed by ALMA and the EHT,” adds Jesse Vos. He is a PhD student at Radboud University, the Netherlands, and was also involved in this study.

The flares were long thought to originate from magnetic interactions in the very hot gas orbiting very close to Sagittarius A*, and the new findings support this idea. “Now we find strong evidence for a magnetic origin of these flares and our observations give us a clue about the geometry of the process. The new data are extremely helpful for building a theoretical interpretation of these events,” says co-author Monika Moscibrodzka from Radboud University.

First Image of Our Black Hole Sagittarius A*

This is the first image of Sgr A*, the supermassive black hole at the center of our galaxy. It’s the first direct visual evidence of the presence of this black hole. It was captured by the Event Horizon Telescope (EHT), an array that linked together eight existing radio observatories across the planet to form a single “Earth-sized” virtual telescope. The telescope is named after the event horizon, the boundary of the black hole beyond which no light can escape. Credit: EHT Collaboration

ALMA allows astronomers to study polarized radio emission from Sagittarius A*, which can be used to unveil the black hole’s magnetic field. The team used these observations together with theoretical models to learn more about the formation of the hot spot and the environment it is embedded in, including the magnetic field around Sagittarius A*. Their research provides stronger constraints on the shape of this magnetic field than previous observations, helping astronomers uncover the nature of our black hole and its surroundings.

Milky Way Central Black Hole Location ALMA

This image shows the Atacama Large Millimeter/submillimeter Array (ALMA) looking up at the Milky Way as well as the location of Sagittarius A*, the supermassive black hole at our galactic center. Highlighted in the box is the image of Sagittarius A* taken by the Event Horizon Telescope (EHT) Collaboration. Located in the Atacama Desert in Chile, ALMA is the most sensitive of all the observatories in the EHT array, and ESO is a co-owner of ALMA on behalf of its European Member States. Credit: ESO/José Francisco Salgado (josefrancisco.org), EHT Collaboration

The observations confirm some of the previous discoveries made by the GRAVITY instrument at ESO’s Very Large Telescope (VLT), which observes in the infrared. The data from GRAVITY and ALMA both suggest the flare originates in a clump of gas swirling around the black hole at about 30% of the speed of light in a clockwise direction in the sky, with the orbit of the hot spot being nearly face-on.

“In the future, we should be able to track hot spots across frequencies using coordinated multiwavelength observations with both GRAVITY and ALMA — the success of such an endeavor would be a true milestone for our understanding of the physics of flares in the Galactic center,” says Ivan Marti-Vidal of the University of València in Spain, co-author of the study.

Milky Way Wide Field View

Wide-field view of the center of the Milky Way. This visible light wide-field view shows the rich star clouds in the constellation of Sagittarius (the Archer) in the direction of the center of our Milky Way galaxy. The entire image is filled with vast numbers of stars — but far more remain hidden behind clouds of dust and are only revealed in infrared images. This view was created from photographs in red and blue light and forming part of the Digitized Sky Survey 2. The field of view is approximately 3.5 degrees x 3.6 degrees. Credit: ESO and Digitized Sky Survey 2. Acknowledgment: Davide De Martin and S. Guisard (www.eso.org/~sguisard)

The team is also hoping to be able to directly observe the orbiting gas clumps with the EHT, to probe ever closer to the black hole and learn more about it. “Hopefully, one day, we will be comfortable saying that we ‘know’ what is going on in Sagittarius A*,” Wielgus concludes.

More information

Reference: “Orbital motion near Sagittarius A* – Constraints from polarimetric ALMA observations” by M. Wielgus, M. Moscibrodzka, J. Vos, Z. Gelles, I. Martí-Vidal, J. Farah, N. Marchili, C. Goddi and H. Messias, 22 September 2022, Astronomy & Astrophysics.
DOI: 10.1051/0004-6361/202244493

The team is composed of M. Wielgus (Max-Planck-Institut für Radioastronomie, Germany [MPIfR]; Nicolaus Copernicus Astronomical Centre, Polish Academy of Sciences, Polen; Black Hole Initiative ved Harvard University, USA [BHI]), M. Moscibrodzka (Institutt for astrofysikk, Radboud University, Nederland [Radboud]), J. Vos (Radboud), Z. Gelles (Center for Astrophysics | Harvard & Smithsonian, USA og BHI), I. Martí-Vidal (Universitat de València, Spania), J. Farah (Las Cumbres Observatory, USA; Universitetet of California, Santa Barbara, USA), N. Marchili (italiensk ALMA Regional Center, INAF-Istituto di Radioastronomia, Italia og MPIfR), C. Goddi (Department of Physics, University of Cagliari, Italia og Universidade de São Paulo, Brasil) , og H. Messias (Joint ALMA Observatory, Chile).

Atacama Large Millimeter/submillimeter Array (ALMA), et internasjonalt astronomianlegg, er et partnerskap mellom ESO, US National Science Foundation (NSF) og National Institutes of Natural Sciences (NINS) i Japan i samarbeid med Republikken Chile. ALMA er finansiert av ESO på vegne av sine medlemsland, av NSF i samarbeid med National Research Council of Canada (NRC) og Ministry of Science and Technology (MOST) og av NINS i samarbeid med Academia Sinica (AS) i Taiwan og Korea Astronomy and Space Science Institute (KASI). ALMA konstruksjon og drift ledes av ESO på vegne av medlemslandene; av National Radio Astronomy Observatory (NRAO), administrert av Associated Universities, Inc. (AUI), på vegne av Nord-Amerika; og av National Astronomical Observatory of Japan (NAOJ) på vegne av Øst-Asia. Joint ALMA Observatory (JAO) sørger for enhetlig ledelse og ledelse av konstruksjon, igangkjøring og drift av ALMA.

European Southern Observatory (ESO) gjør det mulig for forskere over hele verden å oppdage universets hemmeligheter til fordel for alle. Vi designer, bygger og driver observatorier i verdensklasse på bakken – som astronomer bruker til å takle spennende spørsmål og spre fascinasjonen til astronomi – og fremme internasjonalt samarbeid innen astronomi. ESO ble etablert som en mellomstatlig organisasjon i 1962 og støttes i dag av 16 medlemsland (Østerrike, Belgia, Tsjekkia, Danmark, Frankrike, Finland, Tyskland, Irland, Italia, Nederland, Polen, Portugal, Spania, Sverige, Sveits, og Storbritannia), sammen med vertsstaten Chile og med Australia som strategisk partner. ESOs hovedkvarter og dets besøkssenter og planetarium, ESO Supernova, ligger nær München i Tyskland, mens den chilenske Atacama-ørkenen, et fantastisk sted med unike forhold for å observere himmelen, er vert for teleskopene våre. ESO driver tre observasjonssteder: La Silla, Paranal og Chajnantor. Hos Paranal driver ESO Very Large Telescope og Very Large Telescope Interferometer, samt to undersøkelsesteleskoper, VISTA som arbeider i infrarødt lys og VLT Survey Telescope for synlig lys. Også på Paranal vil ESO være vertskap for og drifte Cherenkov Telescope Array South, verdens største og mest følsomme gammastråleobservatorium. Sammen med internasjonale partnere driver ESO APEX og ALMA på Chajnantor, to anlegg som observerer himmelen i millimeter- og submillimeterområdet. På Cerro Armazones, nær Paranal, bygger vi «verdens største øye mot himmelen» — ESOs Extremely Large Telescope. Fra våre kontorer i Santiago, Chile støtter vi våre operasjoner i landet og samarbeider med chilenske partnere og samfunn.

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