Astrophysical jet

An astrophysical jet (hereafter 'jet') is a phenomenon often seen in astronomy, where streams of matter are emitted along the axis of rotation of a compact object. While it is still the subject of ongoing research to understand how jets are formed and powered, the two most often proposed origins are dynamic interactions within the accretion disk or a process from the central object (such as a black hole or neutron star). When matter is emitted at speeds approaching the speed of light, these jets are called relativistic jets, because the effects of special relativity become important. The largest jets are those from black holes in active galaxies such as quasars and radio galaxies. Other systems which often contain jets include cataclysmic variable stars, X-ray binaries and T Tauri stars. Herbig–Haro objects are caused by the interaction of jets with the interstellar medium. Bipolar outflows or jets may also be associated with protostars (young, forming stars), or with evolved post-AGB stars (often in the form of bipolar nebulae).