What is the galactic center

Restlessness in the galactic center

In May 2019, Sagittarius A * - the supermassive black hole in the center of the Milky Way - shone brightly in the infrared spectral range for two and a half hours. The intensity of the eruption exceeded the typical radiation from this region by more than a hundred times. Since then, the galactic center has not come to rest, and astronomers keep registering further bursts of radiation. The most likely cause for the unusual activity is the impact of matter from two extensive gas clouds on the black hole, reports a scientist from the USA in the specialist journal "Astrophysical Journal Letters".

In the center of the Milky Way there is very little gas and stars that could fall into the black hole with 4.6 million times the mass of our sun. Lena Murchikova from the Institute for Advanced Study in Princeton took a closer look at two possible triggers for the unexpected bursts of radiation. On the one hand, S-Objects. These are stars in narrow elliptical orbits around the black hole, which can cause an influx of matter onto the black hole via stellar winds - i.e. gas flowing out of the star's atmosphere. On the other hand, G-objects come into question: They are also located on narrow elliptical orbits, but do not have a point-like appearance, but rather an appearance that is drawn apart along the orbit. This suggests that these are clouds of gas. On the other hand, however, the objects have a high level of stability. They may each contain a star that holds the gas cloud together with its gravitational pull.

Murchikova used theoretical models to estimate how much matter various known objects in the vicinity of Sagittarius A * could have contributed. The scientist combined her results with observational data and came to the conclusion that the objects G1 and G2 cause the radiation bursts registered since May 2019. Because these two G-objects have moved closely past the central black hole in the past few years. If this suspicion is correct, the activity of Sagittarius A * should slowly decrease again. Because G1 and G2 are currently moving away from the black hole. However, if activity continues for more years, astronomers will have to look for another cause of the unrest in the center of the Milky Way.