G2: A gas cloud on its way around the black hole at the Galactic Centre

 

The recent discovery of a gas and dust cloud approximately three times the mass of Earth that is orbiting in the accretion zone of Sgr A* is investigated with the help of numerical modelling.
The observations tightly constrain the cloud's orbit to be highly eccentric, with an innermost radius of approach of only roughly 2,400 times the Schwarzschild radius of the central massive black hole in Sgr~A*. It was reached in 2014 and over the past years the cloud has begun to disrupt, mainly through tidal shearing arising from the black hole's gravitational force. Models to explain this unique object fall in two categories: compact cloud models in which G2 is assumed to be a pure gas and dust cloud and compact source models in which an additional source of gas and dust hides in the observable gas and dust distribution. We find that both models are able to explain the observations equally well and are consistent with a formation of the cloud in the disc of young stars in the GC.
The image shows the example of the evolution of the cloud modelled as a mass losing source, which might be a T-Tauri star. In the latter case the cloud will reform after peri centre passage, allowing to distinguish between the two scenarios.