With the aid of ALMA, scientists have discovered a hot gas bubble that rotates at 30% the speed of light around Sagittarius A*, the galaxy's central black hole.

Utilizing the Atacama Large Millimeter/submillimeter Array, astronomers have detected indications of a 'hot spot' orbiting Sagittarius A*, the galactic center's black hole (ALMA). Our understanding of the environment of our supermassive black hole is improved by the discovery.

We think we are seeing a hot bubble of gas swirling around Sagittarius A* on an orbit that is about the size of Mercury's but completes a full circle in only around 70 minutes. This demands an incredible velocity of nearly 30% of the speed of light! from Germany's Max Planck Institute for Radio Astronomy, Maciek Wielgus. He was the lead author of the study, which was released in the journal Astronomy & Astrophysics today (September 22, 2022).

During an effort by the Event Horizon Telescope (EHT) Collaboration to picture black holes, the observations were taken using ALMA in the Chilean Andes. The European Southern Observatory co-owns ALMA, a radio telescope (ESO). The first-ever image of Sagittarius A*, which was recently released, was made possible by the EHT, which in April 2017 connected eight currently operational radio telescopes globally, including ALMA. Wielgus and his coworkers, who are part of the EHT Collaboration, used ALMA data collected concurrently with the EHT observations of Sagittarius A* to calibrate the EHT data. The study team was surprised to find more hints about the black hole's characteristics in the ALMA-only readings.

Unexpectedly, some of the observations were made soon after an X-ray flare or burst that NASA's Chandra X-ray Observatory had observed coming from the core of our galaxy.

These flares, which have been previously seen with X-ray and infrared instruments, are likely to be connected to heated gas bubbles known as 'hot spots' that orbit the black hole very quickly.

The fact that these flares were previously only plainly visible in X-ray and infrared views of Sagittarius A* is what makes them so novel and intriguing. According to Wielgus, who is also connected to the Nicolaus Copernicus Astronomical Center in Warsaw, Poland, and the Black Hole Initiative at Harvard University, USA, 'here we observe for the first time a very strong signal that circling hot spots are also present in radio data.

According to Jesse Vos, infrared-emitting hot spots become observable at longer wavelengths, such as those seen by ALMA and the EHT, when they cool down. He goes on to speculate that the hot spots seen at infrared wavelengths might be an outgrowth of the same physical phenomena. While obtaining his PhD at Radboud University in the Netherlands, he took part in this investigation.

The most recent discoveries support the long-held hypothesis that magnetic interactions in the extremely hot plasma orbiting extremely close to Sagittarius A* are what generate the flares.