Berlin, September 22 (EFE). – A team of astronomers has detected, through the Atacama Large Millimeter/ Submillimeter Array (ALMA), located in that Chilean desert, signs of a “hot spot” orbiting around Sagittarius A*, the black hole at the center of our galaxy.
This finding helps to better understand the mysterious and dynamic environment of our supermassive black hole, according to a statement released today by the European Southern Observatory (ESO).
“We think we’re looking at a bubble of hot gas slithering around Sagittarius A* in an orbit similar in size to Mercury, but that makes a full loop in just about 70 minutes,” says Maciek Wielgus of the institute. The Max Planck Center for Radio Astronomy in Bonn (Germany) and leader of the study published today in “Astronomy and Astrophysics”.
According to the scientist, “this requires an astonishing speed of about 30% of the speed of light.”
Observations were made with ALMA during the collaborative Event Horizon Telescope (EHT) campaign to image black holes; In April 2017, the EHT connected eight radio telescopes around the world, including ALMA, resulting in the first recently published image of Sagittarius A*.
To calibrate the EHT data, the team around Wielgus used ALMA data recorded simultaneously with the EHT observations of Sagittarius A*, and to their surprise, further clues to the nature of the black hole were hidden only in ALMA measurements.
Coincidentally, some observations were made shortly after a burst or glow of X-ray energy spurted out from the center of our galaxy, detected by NASA’s Chanda Space Telescope.
These types of flares, previously observed with X-ray and infrared telescopes, are believed to be associated with so-called “hot spots”, which are bubbles of hot gas that rotate very quickly and close to the black hole.
According to Willgos, who also belongs to the Nicolaus Copernicus Astronomical Center (Poland), and Harvard University’s Black Hole Initiative (US), “What is really new and exciting is that until now, such flares have been clearly present only in X-ray and infrared observations. red for bow A*”.
“Here we see for the first time a very strong hint that orbital hotspots are also present in radio observations,” he adds.
In the opinion of Jesse Voss, a doctoral student at Radboud University (Netherlands) and co-author of this study, “Perhaps these hotspots detected at infrared wavelengths are a manifestation of the same physical phenomenon.”
Thus, “when infrared hotspots cool, they become visible at longer wavelengths, such as those observed by ALMA and EHT,” he adds.
The flares have long been thought to arise from magnetic interactions in the very hot gas that orbits near arc A*, and 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 about the engineering of the process. The new data are very useful for building a theoretical explanation for these events,” says co-author Monika Mościbrodzka of Radboud University.
According to Ivan Marti Vidal of the University of Valencia, Spain, and co-author of the study, it should be possible in the future to track hotspots across frequencies using coordinated multi-wavelength observations using both the GRAVITY instrument and NASA. ESO’s Long Range Telescope (VLT), as is ALMA.
“The success of such an effort would be a real milestone for our understanding of the physics of flares at the galactic center,” he adds. EFE
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