press release
September 22, 2022
Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have discovered signs of a “hot spot” orbiting Sagittarius A*, the black hole at the center of our galaxy. This discovery helps us better understand the complex and dynamic environment of our supermassive black hole.
“We think we’re dealing with a hot bubble of gas orbiting Sagittarius A* in an orbit similar in size to the planet Mercury, but completing a full orbit in just about 70 minutes. That requires an incredible speed of about 30% of the speed of light.” says Maciek Wielgus of the Max Planck Institute for Radio Astronomy in Bonn, who now heads Astronomy and astrophysics study published.
The observations were made with ALMA in the Chilean Andes – a radio telescope co-sponsored by the European Southern Observatory (ESO) – during a black hole imaging campaign led by the Event Horizon Telescope (EHT) collaboration. In April 2017, the EHT combined eight existing radio telescopes around the world, including ALMA, to create the recently released the first image of Sagittarius A* directed. To calibrate the EHT data, Wielgus and his working group, members of the EHT collaboration, used ALMA data recorded simultaneously with EHT observations of Sagittarius A*. To the team’s surprise, the ALMA measurements revealed further clues about the nature of the black hole.
Some of the observations were made by chance shortly after a burst of X-ray energy from the center of our galaxy by NASA’s space telescope. Chandra has been discovered. These types of bursts, previously observed with X-ray and infrared telescopes, are thought to be associated with so-called “hot spots,” hot bubbles of gas that orbit very quickly and close to the black hole.
“What is really new and interesting is that such flares were previously only clearly visible 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 works at the Nicolaus Copernicus Astronomical Centre in Poland and the Black Hole Initiative at Harvard University in the United States.
“Perhaps these hot spots discovered in infrared wavelengths are a manifestation of the same physical phenomenon: as hot spots radiating in the infrared cool, they become visible at longer wavelengths, like those observed by ALMA and the EHT.” adds Jesse Vos, a doctoral student at Radboud University in the Netherlands, who also participated in the study.
For a long time, it was assumed that the flares were caused by magnetic interactions in the very hot gas that orbits in the immediate vicinity of Sagittarius A*. The new results support this idea.We now find strong evidence for a magnetic origin for these flares, and our observations give us a clue to the geometry of the process. The new data are extremely useful for formulating a theoretical interpretation of this event.e,” says co-author Monika Mościbrodzka of Radboud University.
ALMA allows astronomers to… polarized Studying the radio emission from Sagittarius A*, which can be used to identify the black hole’s magnetic field. The team used these observations along with theoretical models to learn more about how the hotspot formed and the environment it is embedded in, including the magnetic field around Sagittarius A*. Their studies provide stronger clues about the shape of this magnetic field than previous observations and help researchers decipher the nature of our black hole and its surroundings.
The observations confirm some of the previous findingsthat with the GRAVITY-instrument on Very large telescopee (VLT) by ESO, which was observed in infrared. Both GRAVITY and ALMA data suggest that the flare originated from a clump of gas swirling clockwise around the black hole at about 30% the speed of light, with its orbit appearing almost from above.
“In the future, we should be able to track hotspots across multiple spectral ranges through coordinated multi-wavelength observations with GRAVITY and ALMA. Success in such an endeavor would be a real milestone in our understanding of the physics of flares in the galactic center.says Ivan Marti-Vidal of the University of Valencia in Spain, co-author of the study.
The team also hopes to use the EHT to directly observe orbiting clumps of gas to get closer and closer to the black hole and learn more about it.I hope that one day we can say that we really understand what is happening in Sagittarius A*.” concludes Wielgus.
More information
This study was published in the article “Orbital motion near Sagittarius A* – Constraints from polarimetric ALMA observations” published in Astronomy and astrophysics (https://www.aanda.org/10.1051/0004-6361/202244493) appears.
The team is composed of M. Wielgus (Max Planck Institute for Radio Astronomy, Germany (MPIfR); Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Poland; Harvard University Black Hole Initiative, USA (BHI)), M. Moscibrodzka (Department of Astrophysics, Radboud University, The Netherlands (Radboud)), J. Vos (Radboud), Z. Gelles (Center for Astrophysics | Harvard & Smithsonian, USA and BHI), I. Martí-Vidal (Universitat de València, Spain), J. Farah (Las Cumbres Observatory, USA; University of California, Santa Barbara, USA), N. Marchili (Italian ALMA Regional Center, INAF-Istituto di Radioastronomia, Italy and MPIfR), C. Goddi (Dipartimento di Fisica, Università degli Studi di Cagliari, Italy and Universidade de São Paulo, Brazil) and H. Messias (ALMA Joint Observatory, Chile).
The Atacama Large Millimeter/submillimeter Array (ALMA) is an international astronomical facility jointly managed by ESO, the National Science Foundation (NSF) of the United States and the National Institutes of Natural Sciences of Japan (NINS), in cooperation with the Republic of Chile. ALMA is supported by ESO on behalf of its Member Countries, by NSF in cooperation with the National Research Council of Canada (NRC), the Ministry of Science and Technology (MOST) and NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Institute of Astronomy and Space Science (KASI). In terms of development, construction and operation, ESO leads the European contribution, the National Radio Astronomy Observatory (NRAO), which is in turn operated by Associated Universities, Inc. (AUI), the North American contribution, and the National Astronomical Observatory of Japan (NAOJ) for the East Asian contribution. The Joint ALMA Observatory (JAO) is responsible for the overall project management for ALMA construction, commissioning and observation operations.
The European Southern Observatory (ESO) enables scientists from around the world to unlock the secrets of the universe for the benefit of all. We design, build and operate world-class observatories that astronomers use to answer exciting questions and inspire fascination with astronomy, and we promote international collaboration in astronomy. Founded in 1962 as an intergovernmental organisation, ESO is led by 16 Member States (Belgium, Czech Republic, Denmark, Germany, France, Finland, Ireland, Italy, the Netherlands, Austria, Poland, Portugal, Sweden, Switzerland, Spain and the United Kingdom) and the Host Country Chile and Australia as strategic partners. ESO Headquarters and its Visitor Centre and Planetarium, ESO Supernova, are located near Munich in Germany, while the Atacama Desert in Chile, a wonderland offering unique conditions for observing the skies, is home to our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its associated Very Large Telescope Interferometer, as well as two survey telescopes, the infrared VISTA and the visible-light VLT Survey Telescope. Also at Paranal, ESO will operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. In collaboration with international partners, ESO operates the 2-millimetre and submillimetre sky-observing facilities APEX and ALMA on Chajnantor. On Cerro Armazones, near Paranal, we are building “the world’s largest eye in the sky”: ESO’s Extremely Large Telescope. From our offices in Santiago, Chile, we support our activities in the country and work with Chilean partners and society.
The translations of ESO press releases into English are a service of the ESO Science Outreach Network (ESON), an international astronomy outreach network in which scientists and science communicators from all ESO Member Countries (and some other countries) are represented. It is the German node of the network. House of Astronomy in Heidelberg.
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Contact details
Maciek Wielgus
Max Planck Institute for Radio Astronomy
Bonn, Germany
Tel: +48 602417268
E-mail: maciek.wielgus@gmail.com
Monika Moscibrodzka
Radboud University
Nijmegen, Netherlands
Tel: +31-24-36-52485
E-mail: m.moscibrodzka@astro.ru.nl
Ivan Marti Vidal
University of Valencia
Valencia, Spain
Tel: +34 963 543 078
E-mail: i.marti-vidal@uv.es
Jesse Vos
Radboud University
Nijmegen, Netherlands
Mobile: +31 6 34008019
E-mail: jt.vos@astro.ru.nl
Barbara Ferreira
ESO Media Manager
Garching near Munich, Germany
Mobile: +49 151 241 664 00
E-mail: press@eso.org
Markus Nielbock (press contact Germany)
ESO Science Outreach Network and House of Astronomy
Heidelberg, Germany
Tel: +49 6221 528-134
E-mail: eson-germany@eso.org
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This is a translation of ESO press release eso2212.