What is the designation of the supermassive black hole at the center of the Milky Way Galaxy?

The designation of the supermassive black hole at the center of the Milky Way Galaxy is Sgr A*. This black hole, located near the galactic center in the constellation Sagittarius, has been the focus of extensive astronomical studies. It is characterized by its relatively modest mass, around four million times that of our Sun, especially when compared to other supermassive black holes found in other galaxies.

The designation "Sgr A*" specifically indicates that it is a prominent source of radio emissions, with the asterisk denoting its status as an active center. Unlike Cygnus X-1, which is a well-known stellar black hole in the Cygnus constellation, Sgr A* is much more massive and is not associated with direct observation of X-rays in the same way.

M87*, on the other hand, refers to the supermassive black hole in the center of the Messier 87 galaxy, which gained fame for being the first black hole imaged by the Event Horizon Telescope. Lastly, SGR B2 is a different astronomical object, specifically a bright radio source associated with a molecular cloud near the Galactic Center, and not a black hole.

Thus, Sgr A* is the correct answer as it uniquely designates