WHAT IS SGR A*? The Starved Black Hole in the Center of the Milky Way
  Sgr A* is the unique 1 Jy flat spectrum radio point source located at the dynamical center of the Galaxy and in the very center of the central star cluster. Due to its unusual appearance it has long been speculated that this source is powered by a supermassive black hole. The enormous increase in observational data obtained for Sgr A* in recent years has enabled us to develop, compare and constrain a variety of models for the emission characteristics of this source. Because of its relative proximity and further observational input to come Sgr A* may therefore become one of the best laboratories for studying supermassive black hole candidates and basic AGN physics. This paper briefly summarizes our current understanding of this enigmatic radio source and compares various models, i.e. disk/jet and wind-accretion models. 
Heino Falcke