Polar jet#Relativistic jet
A cosmic jet in astronomy is a directed ( collimated ) gas stream.
Jets are formed when an object gas accumulates from a rotating disk ( accreted ). Only part of the gas reaches the disc object, the other part flows perpendicularly to the rotation plane away from the object. The collimation is either purely geometric concluded by the inner edge of the accretion disk or by magnetic fields.
Jets come in virtually all of a disk accreting objects in front of black holes up to nascent (especially in active galactic nuclei ) protostars. The jets of quasars can be many thousands of light-years long and move at nearly the speed of light. In jets, which move with at least 70.7 percent of the speed of light and in an angular range of (-90 °, 90 ° ) to the observer, it can even lead to an apparent superluminal speed. This can be explained so that the light of the approaching jets requires a shorter and shorter time to reach the observer. Thus, it looks to the observer as if the jet in the transverse direction moving faster than light. Jets, which do not move in the above angular range, so move away from the observer, appear correspondingly slower because the light has to travel a longer and longer instead of shorter path in this case. Are they moving in, however, purely transverse direction, so can their real speed can be observed.
If Jets take on dense interstellar matter, a shock front is formed. When jets of protostars, T Tauri stars and Herbig-Ae/Be-Sternen these shock waves Herbig -Haro objects are called. In stellar astrophysics jets have also been detected in interacting binary systems such as symbiotic stars, X-ray binaries and cataclysmic variables. In the case of active galactic clouds mainly in the radio range are easily measurable. Ten active galactic nuclei (mostly Blazars ) were measured by the EGRET and COMPTEL telescope in the high energy MeV to GeV range. As an explanation of the source of this exceptionally high-energy radiation different models are discussed, including the " low-energy " synchrotron radiation of the jet itself, which is scattered in this energy regime by the inverse Compton effect by collisions with high-energy Jetelektronen, or photons that are scattered by the clouds in the plane and there is also an inverse Compton scattering to suffer higher energies.
Jets are sources of a non-isotropic radiation of energy, since radiate accelerated to relativistic velocity jets most of the energy in their direction of propagation. According to current hypotheses, both the long gamma -ray bursts as well as the ultra- luminous X-ray sources Strengthening no isotropic radiator with an energy of 1052 erg, but emit their proven electromagnetic radiation along a jet axis with dimensions of only a few degrees.
For the formation of jets magneto hydrodynamic processes are important, the details are not yet fully understood. Jets are getting associated with accretion, the accretion of matter from the zirkustellaren environment or from a companion star onto a compact object, observed with the angular momentum is dissipated effectively from an accretion disk with a highly collimated magnetic discharge. After today's presentation, the energy and the angular momentum of the disk is extracted by a magnetic torque, which is caused by a coiled magnetic field in the accretion disk. If the inclination angle is small enough magnetic forces can accelerate the matter along the field lines. Beyond the Alfvénpunktes the matter is accelerated by the Lorentz force. The collimation of the jet is achieved by means of magnetic forces due to the toroidal structure of the magnetic field or by a higher gas pressure in the corona of the accretion.