Relativistic jet
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Relativistic jets are extremely powerful jets of plasma which emerge from the centers of some active galaxies, notably radio galaxies and quasars. A jet is created from subatomic particles and magnetic fields in the accretion disk of the supermassive black hole in the nucleus of an active galaxy. It is believed that the twisting of magnetic fields in the accretion disk collimates the outflow along the rotation axis of the black hole, so when conditions are suitable, a jet will emerge from each face of the accretion disk. If the jet is oriented along the line of sight to earth, relativistic beaming will change its apparent brightness.
Similar jets, though on a much smaller scale, can develop around the accretion disks of neutron stars and stellar black holes. These systems are called microquasars. A famous example is SS433, whose well-observed jet has a velocity of 0.23c, although other microquasars appear to have much higher (but less well measured) jet velocities. Even weaker and less-relativistic jets may be associated with many binary systems; the acceleration mechanism for these jets may be similar to the magnetic reconnection processes observed in the Earth's magnetosphere and the solar wind.
Although a disk's magnetic field and rotation are believed responsible for the formation of the axial radiation jet, the observed jets are more tightly collimated than predicted by current theory.
It is believed that the formation of relativistic jets is the key to explaining the production of gamma-ray bursts. These jets have Lorentz factors of ~ 100, making them the fastest celestial objects currently known.
Some jets are associated to binary systems. A good example is the pulsar in the Crab Nebula (M1) In that case the fundamental mechanism of forming and accelerating of these jets is to be linked to what is supposed to be with the solar wind and the Earth magnetosphere.
External links
- http://perso.wanadoo.fr/lempel/jets_and%20binary_systems-02.pdf
- http://www.cetp.ipsl.fr/1gdpub/21phspa/concepts/sous-orage/sous-orage-magnetique.html
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