By Chris Skeldon 
cWith the help of the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have detected signs of a “hot spot” orbiting around Sagittarius A*, the black hole at the center of our galaxy. This discovery helps us better understand the mysterious and dynamic environment that surrounds our supermassive black hole.
“We think we see a bubble of hot gas around Sagittarius A*, in an orbit similar in size to Mercury, but completing a revolution in about 70 minutes. For that to happen, the speed at which he was moving would have to be enormous, about 30% the speed of light!Explains Masek Wilgus of the Max Planck Institute for Radio Astronomy in Bonn, Germany, who led the study published in the specialist journal. Astronomy and astrophysics.
Obtaining notes with spirit In the Chilean Andes – a radio telescope partly owned by the European Southern Observatory (ESO) – during a campaign by the EHT Collaboration (Event Horizon Telescope) to image black holes. In April 2017, the EHT joined forces with eight radio telescopes located around the world, including ALMA, to obtain data that led to The first image of Sagittarius A* was recently released. To calibrate the EHT data, Wielgus and colleagues, members of the EHT Collaboration, used ALMA data captured at the same time as the EHT observations of Sagittarius A*. To the team’s surprise, there was more clues hidden in the measurements obtained only with ALMA about the nature of the black hole.
By chance, some observations were made shortly after the burst of X-ray energy emitted from the center of our galaxy, which was detected by Chandra Space Telescope from NASA. These types of eruptions, previously observed with infrared and X-ray telescopes, are believed to be associated with so-called “hot spots,” bubbles of hot gas moving at high speeds in orbits very close to the black hole.
“What is really new and interesting is the fact that, so far, such eruptions are clearly present only in infrared and X-ray observations of the A* arc. We are seeing for the first time strong indications that hot spots orbiting a black hole are also present in radio observations,Willgus, also affiliated with the Nicolaus Copernicus Astronomical Center, Poland, and the Black Hole Initiative at Harvard University, USA.
“These hot spots detected at infrared wavelengths are probably a manifestation of the same physical phenomenon: as they cool, infrared hot spots become visible at longer wavelengths, such as those observed by ALMA and EHT.‘,” adds Jesse Vos, a doctoral student at Radboud University, the Netherlands, who was also involved in this study.
It has long been thought that these eruptions arise from magnetic interactions of the superheated gas circulating near arc A*, and indeed these new findings support this idea. “We have now found strong evidence for a magnetic origin for these eruptions and our observations give us clues about the engineering of the process. The new data is very useful in constructing a theoretical explanation for these events,Says co-author Monica Mościbrodzka of Radboud University.
ALMA allows astronomers to study radio emissions polarized From arc A*, which can be used to examine the black hole’s magnetic field. The team used these observations along with theoretical models to learn more about the formation and environment of the hotspot, including the magnetic field surrounding the A* arc. This research work places stronger boundaries on the shape of this magnetic field than those achieved in previous observations, helping astronomers discover the nature of our black hole and its surroundings.
Notes confirm some of the Previous discoveries Made with the help of the instrument gravity mounted on very large telescope (VLT) from ESO, which it monitors in the infrared. Both the GRAVITY and ALMA data indicate that the explosion originates from a knot of gas orbiting the black hole at about 30% of the speed of light clockwise across the sky, with the hotspot orbiting almost head-on.
“In the future, we should be able to track hotspots across multiple frequencies using coordinated multi-wavelength observations obtained with both GRAVITY and ALMA – the success of such an effort will be a milestone in our understanding of the physics of explosions in the field. Galactic Centersays Ivan Marti Vidal of the University of Valencia, Spain, co-author of the study.
The team also hopes to be able to observe gas nodes using EHT, to discover more about the black hole and learn more about it. “Maybe one day we’ll be comfortable enough to say that we “know” what’s going on in bracket A*,Wielgus concludes.