What is a supermassive black hole?

A supermassive black hole is defined as a black hole that possesses a mass ranging from millions to billions of times that of our Sun. These colossal entities are typically found at the centers of galaxies, including our own Milky Way. The formation of supermassive black holes is still a topic of active research, but they are believed to have grown through processes such as the merging of smaller black holes and the accumulation of mass from surrounding gas, stars, and other materials over time.

Their immense gravitational pull influences the motion of stars and gases in their vicinity, shaping the dynamics and evolution of their host galaxies. This is contrasted with smaller black holes, which may only have a stellar mass, typically formed from the gravitational collapse of massive stars after they have exhausted their nuclear fuel.

The other choices highlight aspects that do not accurately capture the essence of supermassive black holes. For example, options referring to smaller black holes or specific emissions like x-rays do not relate to the broad definition that sets supermassive black holes apart due to their extraordinary mass and impact on galactic formation and dynamics.