The black hole Sagittarius a*, at the center of our galaxy, could rotate at dizzying speeds, touching the limit imposed by the theory of relativity.

At the center of our galaxy there is a supermassive black hole Sagittarius a* (the asterisk indicates the presence of a black hole) which could rotate at dizzying speeds, touching the limit imposed by the theory of relativity. The researchers, led by Michael Janssen of Radboud University (Netherlands), analyzed the data of the event Horizon Telescope (Eht) of 2017, supported by advanced artificial intelligence techniques. The searches were published in Astronomyastrophysics.

Help from the neural network. To identify parameters such as the rotation speed and the magnetic structure, first they generated simulations of about one million black holes, with sophisticated numerical models and supercomputer, then trained one neural network Composed of basic units, artificial neurons called, organized in layers that process and transmit information. Each neuron receives input, weighs them based on importance and, through an activation function, decides whether to “activate” to send the signal to the next level. Through a learning process, which implies weight adjustment based on the errors made, the network is able to recognize complex patterns, make predictions and make autonomous decisions. When the IA examined the real data of Sgr a*, he reported stunning results: The black hole runs between 80% and 90% of its maximum theoretical speed, with the rotation axis aligned with the earth. In addition, the algorithm has reported discrepancies in the models used for magnetic fields: nobody adapts perfectly, suggesting the need for further mathematical developments.

Rotation speed. The rotation of a black hole is described by an expert parameter called “A*” which varies from 0 (no spin, ie no rotation) to 1 (maximum rotation compatible with relativity). Studies based on X -rays and radio have suggested values ​​between 0.60 and 0.96. In particular, the “Outflow Method” – which uses the flow of radio emissions and X -rays – has estimated to* ≈ 0.90 ± 0.06. The analysis of emissions observed by Eht instead indicated a value around 0.9. More “classic” studies, based on star orbits, had instead proposed lower limits, even with A* <0.1, to indicate that there is little influence on the orbital level of the surrounding stars.

Astrophysical implications. A quick black hole blends rotational energy and Lense -Thirring effect (also called drag effect) or the phenomenon predicted by the general relativity in which a massive body in rotation drags spacetime “, drastically altering the geometry of its around. This influences the dynamics of the growth disc, the emission of X -rays and radio and even the formation of any jets. “Every new esteem enriches our picture of the Galactic evolution and the interactions between black holes and close stars,” said Jansen.