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

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While studying the supermassive black hole at the center of our galaxy, Sagittarius A*, researchers made a strange discovery: a bubble of incandescent gas spinning around it at a very high speed! A phenomenon explained by the eruption of black holes On May 12, 2022, the Event Horizon Telescope (EHT) released the first image of the central black hole in our GalaxyGalaxy. Sagittarius A* was visible for the first time, along with its discaccretion accretion disc. Located in the heart of the Milky Way Milky Way, 27,000 light-years from Earth, Sagittarius A * will have given scientists a hard time: it took five years of hard work to imagine it. In fact, the observations on which it is based date back to 2017, and were made by an array of eight radio telescopes, including the Atacama Large Millimeter/submillimeter Array (Alma), located at the European Southern Observatory (ESO) in Chile . .From With these observations made by Alma, researchers are trying to deduce the properties of our black hole and its environment. And luckily for them, they detected a strange phenomenon there, detailed in a study in Astronomy & Astrophysics: a hotspothotspot orbiting at high speed around Sagittarius A*! “We think we’re seeing a bubble of bright gas sliding around Sagittarius A* in an orbit similar in size to the planet Mercury, but completing a full revolution in just about 70 minutes. This requires a mind-boggling speed of about 30% of the speed of the speed of light! Maciek Wielgus enthuses in an ESO statement, first author of the study and astronomer astronomer at the Max Planck Institute for Radio Astronomy in Bonn, Germany The black hole supermassive Sagittarius A*, imaged by the Event Horizon Telescope (EHT) collaboration, along with an artist’s impression of the hotspot’s location and its orbit around the black hole, based on modeling forecast data Alma. © Collaboration EHT, ESO, M. Kornmesser, M. WielgusThe center of the galaxy has explodedAccording to the study, this hotspot finds its explanation in the eruption of black holes. In fact, the observations used by the researchers van dat ar on both April 6 and 7, 2017, and April 11, 2017. However, an eruption of the black hole Sagittarius A * occurred just before these latest observations, detected in X-rays by X-rays by the Chandra Space Telescope. The data collected by the researchers, curves of polarized light, then changed and they interpreted it as the generation of a hot spot rotating at high speed around the black hole. Because the change in the polarized light curve indicates a change in the magnetic fields surrounding the black hole. And for researchers, 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 building a theoretical interpretation of these events,” says Monika Mościbrodzka, co-author of the study and astronomer at Radboud University. These black hole eruptions resemble those that occur on the surface of our star, the Sun, which cause auroras. In the case of a black hole, the hot gas that orbits very quickly around it forms an accretion disk. Inside the disc, the matter heats up to millions of degrees, which transforms into plasma, therefore into ionized and magnetized gas. Due to the extreme conditions of temperature, pressure, speed, which prevail in the disc, different magnetic fields are generated, which interact with each other and twist. When these fields meet, they can reconnect or reconfigure, resulting in what is called magnetic reconnection. Some of the energy accumulated before reconnection is ejected, either in the form of X-rays, heat-heat or even matter directly. And that’s what the researchers observed: a bubble of bright gas, “orbiting clockwise in an innermost region of the accretion flow,” the study describes, cooling the plasma emitted during the eruption Finally, in addition to indicating an eruption of Sagittarius A*, these observations testify to a new phenomenon: the cooling of the jets of plasma emitted by this eruption that remain in orbit around the black hole. “What’s really new and interesting is that until now these flares have only been clearly present in X-ray and infrared observations of Sagittarius A*. Here we see for the first time a very strong indication that orbiting hot spots are also present in radio observations”, explains Maciek Wielgus. In fact, the fact that this gas bubble has been observed in radio waves indicates a rather low temperature, these waves being much less energetic than X-rays or infrared.” Perhaps these infrared-emitting hot spots are a manifestation of the same physical phenomenon: as the infrared-emitting hot spots cool, they become visible at longer wavelengths, such as those observed by Alma and EHT,” adds Jesse Vos, co-author of the study and PhD student at Radboud University in the Netherlands. Subsequently, the researchers aim to further focus on this phenomenon, in particular through observations at mb the EHT. “Hopefully one day we’ll be able to claim that we ‘know’ what’s going on in Sagittarius A*,” concludes Maciek Wielgus.
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