The giant black hole at the center of our galaxy has erupted, and astronomers have seen it all!

While studying the supermassive black hole at the center of our galaxy, Sagittarius A*, scientists made a strange discovery: a bubble of glowing gas spinning around it at very high speed! A phenomenon that is explained by the eruption of black holes.

On May 12, 2022, the very first image of our central black hole was taken GalaxyGalaxy was revealed byEvent Horizon Telescope (EHT). Sagittarius A* was visible for the first time along with its accretion diskaccretion disk. Located in the heart of The Milky WayThe Milky Wayto 27,000 light yearslight years from Earth, Sagittarius A* will have given scientists difficulties: five years of hard work were needed to put it into the picture. The observations on which it is based actually date from 2017 and were carried out by a network of eight radio telescopesradio telescopesincluding L’Atacama Large Millimeter/submillimeter Array (Alma), located at the European Southern Observatory (ESOESO) in Chile.

From these observations made by Alma, scientists are trying to deduce the properties of our black hole and its environment. And luckily for them, they discovered a strange phenomenon there, detailed in a study by Astronomy and astrophysics : a hotspothotspot circling high velocityvelocity all the way around Sagittarius A*! “We think we are looking at a gas bubble incandescent lampincandescent lamp glides around Sagittarius A* on a orbitorbit similar in size to the planet Mercury, but makes a full rotation in only about 70 minutes. This requires an astonishing speed of about 30% of the speed of lightthe speed of light ! », enthused Maciek Wielgus in a press release from ESO, first author of the study and astronomerastronomer to Max Planck Institute for RadioRadio astronomy in Bonn, Germany.

The supermassive black hole Sagittarius A*, imaged by the Event Horizon Telescope Collaboration (EHT), along with an artist’s impression of the location of the hotspot and its orbit around the black hole, based on modeling forecast data from Alma. © EHT Collaboration, ESO, M. Kornmesser, M. Wielgus

The center of the galaxy has erupted

According to the study, this hot spot finds its explanation in the eruption of black holes. The observations used by the researchers actually dated both April 6 and 7, 2017, and April 11, 2017. However, an eruption of the black hole Sagittarius A * occurred just before these last observations, which were detected in them X-raysX-rays talk space telescopespace telescope Chandra. The data collected by the researchers, curves of polarized light, then changed, and they interpreted them as the generation of a hot spot spinning at high speed around the black hole. Because the change of the curve of polarized light indicates a change of magnetic fieldsmagnetic fields around the black hole.

And for scientists, this is proof that everything is played by magnetic fields! “Now we find strong evidence for a magnetic origin of these flares, and our observations give us a clue about the geometry of the process. The new data are extremely useful for constructing a theoretical interpretation of these events.” explains Monika Mościbrodzka, co-author of the study and astronomer at Radboud University. These black hole eruptions are similar to those taking place on our surface starstarThe Sun, at the origin of polar northern lightspolar northern lights.

In the case of a black hole gasgas hot which orbits very rapidly around it forms an accretion disk. Within the disk is fabricfabric is so heated to millions of degrees that it changes to plasma, therefore to ionized and magnetized gas. Due to extreme temperature conditions, pressurepressure, speed prevailing in the disc, different magnetic fields are generated which interact with each other and twist. When these fields meet, they can reconnect or reconfigure, leading to what is called magnetic reconnection. A part ofenergyenergy accumulated before reconnection then ejected, whether in the form of X-rays, heatheator even directly from fabric. And that’s what the researchers observed: a bubble of glowing gas,” circling clockwise in an inner region of the accretion flow”describes the study.

These observations testify to the cooling of the plasma emitted during the eruption

Finally, in addition to indicating an outburst of Sagittarius A*, these observations testify to a new phenomenon: the cooling of the plasma jets emitted by this outburst, which remain in orbit around the black hole. “What is really new and interesting is that such flare-ups have so far only been clearly present in X-rays and infraredinfrared of Sagittarius A*. Here we see for the first time a very strong indication that orbiting hotspots are also present in radio observations.” explains Maciek Wielgus.

The fact that this gas bubble was observed in radio waves actually indicates a fairly low temperature, as these waves are much less energetic than X-rays or infrared. “Perhaps these hot spots detected under infrared waves are a manifestation of the same phenomenon physicalphysical : as soon as the hot points emitting in the infrared cool down, they become visible i wavelengthswavelengths longer, like those observed by Alma and EHT”, adds Jesse Vos, study co-author and PhD student at Radboud University in the Netherlands. Subsequently, the researchers intend to focus even more on this phenomenon, especially through observations with the EHT. “Hopefully one day we will be able to claim that we ‘know’ what is going on in Sagittarius A*”concludes Maciek Wielgus.

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