What type of celestial object is a supermassive black hole thought to power?

A supermassive black hole is thought to power active galactic nuclei, which are luminous regions at the centers of some galaxies, including quasars and blazars. These nuclei are extremely bright and can outshine entire galaxies due to the immense energy released as matter falls into the black hole. This process occurs when gas and dust from surrounding space spiral inwards, creating an accretion disk that heats up and emits radiation across the electromagnetic spectrum, particularly in the X-ray range.

In contrast, neutron stars and white dwarfs are remnants of massive stars that have undergone supernova explosions or exhausted their nuclear fuel and collapsed under gravity, but they do not have the same capabilities to power enormous energy outputs like supermassive black holes do. Comets, composed mostly of ice and dust, are not associated with the energy generation mechanisms typical of active galactic nuclei and differ significantly from the phenomena driven by supermassive black holes. Thus, the relationship between supermassive black holes and active galactic nuclei is a defining characteristic of some of the most energetic and extreme environments in the universe.