Which object in the sky is referenced as a “supermassive black hole”?

The reference to "supermassive black hole" specifically points to Sagittarius A* (Sgr A), which is the supermassive black hole located at the center of our Milky Way galaxy. This black hole has a mass equivalent to millions of times that of our Sun, which fits the definition of a supermassive black hole. These enormous gravitational entities play a crucial role in the dynamics of galaxies, influencing their formation and evolution.

In contrast, the other options refer to different types of astronomical objects. A Black Widow Pulsar is a type of neutron star that is gaining mass from a companion star. V404 Cygni and Cygnus X-2 are both X-ray binary systems that contain a stellar black hole rather than a supermassive one. Stellar black holes typically have masses that range from about three to several tens of solar masses, significantly less than that of supermassive black holes. Understanding these categories helps to clarify the unique characteristics and scales of various cosmic entities.