Relativistic jet

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Relativistic Jet. The environment around the AGN where the relativistic plasma is collimated into jets which escape along the pole of the supermassive black hole

Relativistic jets are extremely powerful jets of plasma which emerge from the centers of some active galaxies, notably radio galaxies and quasars. It is believed that the twisting of magnetic fields in the accretion disk collimates the outflow along the rotation axis of the central object, 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.

Observations of jets with the Swift spacecraft determined that the jets, which have long been known to be electrically neutral, are formed of electrons and protons. The jets also carry much more energy than was originally believed. Measures of X-rays peaked at 10,000 electronvolts. The jets are calculated to move at 99.9% of the speed of light and carry as much mass as the planet Jupiter.^[1]

Elliptical Galaxy M87 emitting a relativistic jet, as seen by Hubble Space Telescope's Wide Field and Planetary Camera 2 in the visible spectrum.

Similar jets, though on a much smaller scale, can develop around the accretion disks of neutron stars and stellar black holes. These systems are often 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.

The M87 jet seen by the Very Large Array in radio frequency (the viewing field is larger and rotated with respect to the above image).

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 one of 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.