Sagittarius A*
The radio source is part of a larger astronomical feature known as Sagittarius A. Sagittarius A* is thought to be a supermassive black hole, like those that are at the centers of most spiral and elliptical galaxies. Observations of the star S2 in orbit around Sagittarius A* were used to show the presence of the Milky Way's central supermassive black hole. This led to the conclusion that Sagittarius A* is the site of that black hole.