jet

A jet (or polar jet) is a stream of matter (e.g., plasma) sent with apparent force from an astronomical body such as a black hole. Their mechanism is not agreed upon, but magnetism (e.g., magnetic field under rotation) is presumed to be a component. Bodies with accretion disks such as protostars, neutron stars often show jets as well as active galaxies often show jets sent in one or both directions along the axis of rotation, polar jets or disk wind. A relativistic jet is one in which matter is emitted at speeds approaching c.

For active galaxies, they are termed AGN jets or galactic jets. Some galaxies have are bent jets (with a curve rather than straight), which are of research interest. In the case of stars (stellar jets), high stellar rotation makes them oblate, and the surface at the poles is nearer the core, thus hotter, contributing to jet formation.

The terms visible jet and radio jet are used for visible light and radio images of (and data regarding) jets, typically AGN jets. Analogous more specific terms are also used, such as VLBI jet and VLA jet for very-long-baseline interferometry (VLBI) and Very Large Array (VLA) images of jets.

The word jet is also sometimes short for jet stream, a type of wind on a planet (see zonal flow),