What is an accretion disk?

An accretion disk is a structure formed by diffused material in orbital motion around a central body, typically a star, black hole, or young stellar object. In this scenario, the gas and dust particles gradually spiral into the central object due to gravitational forces. As material moves toward the central object, it gains kinetic energy and converts it into thermal energy, often heating the disk and emitting radiation.

This phenomenon occurs commonly in various astrophysical contexts. For instance, around newly formed stars, accretion disks are crucial to the formation of planets. They can also be present around black holes, where the intense gravitational pull drives matter to extreme temperatures and speeds, often resulting in the emission of X-rays detectable from great distances.

Understanding this concept is vital because it explains many processes in stellar evolution, galaxy formation, and even phenomena such as quasars and active galactic nuclei.