Sagittarius A* (Sgr A*) is an intense and very compact source of radio waves located in the centre of the Milky Way, specifically in the constellation.

Sgr A* is also the location of an extremely massive compact object in our Galaxy - 4 million times more massive than the Sun - a characteristic component of the centres of many elliptical and spiral galaxies.

Scientists R. Genzel and A. Ghez won the 2020 Nobel Prize in Physics for the identification of this "celestial monster". Their measurements of the movement of stars in the Galaxy's central region were so precise that they contributed to proving the existence of this object, which is most likely a supermassive black hole.

Actually, the existence of black holes and the presence of compact supermassive objects in galaxies other than our own seems to be beyond doubt. However, while the origin of so-called stellar black holes has an established physical explanation (they are the remnants of massive stars that are now extinct), the origin of supermassive black holes is still uncertain.

A new study coordinated by Roberto Capuzzo Dolcetta of the Department of Physics at Sapienza University of Rome, in collaboration with the École Normale Supérieure in Paris, shows how the formation of the supermassive black hole at the centre of our Galaxy may result from the notably rapid aggregation, through successive collisions, of a "packet" of lighter black holes, transported to the centre of the Galaxy by the star clusters that housed them, which orbited losing progressively energy until they merged.

The study results, published in the journal Monthly Notices of the Royal Astronomical Society, were obtained through sophisticated and high-precision numerical simulations, conducted also on computers at the Amaldi Research Centre at Sapienza.

References:

Dynamics of a superdense cluster of black Holes and the formation of the Galactic supermassive black hole - Pauline Chassonnery, Roberto Capuzzo Dolcetta - Monthly Notices of the Royal Astronomical Society 2021 https://doi.org/10.1093/mnras/stab1016

Further Information

Roberto Capuzzo Dolcetta 
Department of Physics
roberto.capuzzodolcetta@uniroma1.it