Accretion Disks & Relativistic Jets: Structures & Vocabulary

Gas approaching a compact object usually carries angular momentum, so it cannot fall straight inward. Instead it forms an accretion disk where orbital energy is converted into heat and radiation, sometimes powering luminosities far greater than those of ordinary stars. Some accreting black holes and neutron stars also launch narrow relativistic jets.

Viscous and magnetic stresses transport angular momentum outward, allowing matter to spiral inward and release gravitational binding energy. Magnetized rotating plasma near a compact object can collimate outflows and, for spinning black holes, potentially extract rotational energy through electromagnetic processes.

X-ray binaries show hot inner disks and rapid variability, active galactic nuclei display bright multiwavelength continua and radio jets, and very-long-baseline interferometry resolves relativistic jet motion and structures near supermassive black holes.

Disk systems may include a cool optically thick disk, hot corona, winds, magnetic fields, and an inner edge tied to compact-object properties. Jets form along the rotation axis and can extend beyond their host galaxies.