Astronomers using the ALMA spotted a "hot spot" around Sagittarius A*, the black hole at the center of our galaxy. Astronomers will be able to better understand the environment of our black hole.
We think we're looking at a hot bubble of gas zipping around Sagittarius A* and making a full loop in 70 minutes. Maciek Wielgus of the Max Planck Institute for Radio Astronomy in Bonn, Germany, is the lead author of the study.
During the campaign to image black holes, the observations were made with ALMA, a radio telescope co- owned by the European Southern Observatory. The first ever image of Sagittarius A* was released by ALMA after it was linked with eight other radio telescopes. The ALMA data was recorded simultaneously with the EHT observations of Sagittarius A*. The team was surprised to find more clues to the nature of the black hole.
Some of the observations were done after a burst of X-ray energy was seen by the Chandra Space Telescope. These flares are thought to be associated with hot spots that are close to the black hole.
It's new and interesting that the flares were only visible in X-ray and infrared observations. "Here, we see for the first time a very strong indication that hot spots are also present in radio observations, and that's something we've never seen before."
As hot spots cool down, they become visible at longer wavelength, like the ones observed by ALMA and the EHT.
The flares were thought to be the result of magnetic interactions in the very hot gas around Sagittarius A*. We found strong evidence for a magnetic origin of the flares and our observations gave us a clue about the geometry of the process. The new data can be used to build a theoretical interpretation of these events.
Resolving the black hole's magnetic field can be done with the help of ALMA. The team used the observations to learn more about the hot spot and the environment it is embedded in. The shape of the magnetic field is more constrained by their research than previous observations.
Some of the previous discoveries made by the GRAVITY instrument have been confirmed by the observations. According to the data from GRAVITY and ALMA, the flare originated in a clump of gas swirling around the black hole at a rate of 30% of the speed of light.
The success of such an endeavor would be a true milestone for our understanding of the physics of flares in the Galactic center.
To learn more about the black hole, the team hopes to be able to observe the gas clumps with the EHT. One day, we will be able to say that we know what is happening in Sagittarius A*.
The paper "Orbital motion near Sagittarius A*--Constraints from polarimetric ALMA observations" was published in Astronomy and Astrophysics.
More information: M. Wielgus et al, Orbital motion near Sagittarius A*, Astronomy & Astrophysics (2022). DOI: 10.1051/0004-6361/202244493 Journal information: Astronomy & Astrophysics
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