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:''The lower-energy non-relativistic version of this phenomenon is described at polar jet.''

'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]

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.

Reva Kay Williams, University of Florida, has provided an explanation for the immense power of relativistic jets. She developed a proof of Roger Penrose's mechanism from gravitomagnetism for extracting energy and momentum from rotating Kerr black holes.^[2][3][4] Her model shows that the Lense-Thirring effect (frame dragging) produced by a spinning black hole can account for the observed high energies and luminosities of quasars and active galactic nuclei; the collimated jets about the polar axis; and asymmetrical jets (relative to the orbital plane). They are inherent properties of Kerr black holes. Those properties have not been adequately described by magnetohydrodynamics (MHD). In fact, MHD is not needed to explain the formation and collimation of jets.^[5] MHD has been used in explanations for the collimer flow of polar jets. Williams’ application of Penrose’s mechanism can be applied to any size black hole.^[6] Relativistic jets can serve as the most dramatic form of validation for frame dragging.
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.

Contents

See also

Further reading

References

External links

See also

★ Bipolar outflow

Further reading

★ Melia, Fulvio, ''The Edge of Infinity. Supermassive Black Holes in the Universe'' 2003, Cambridge University Press, ISBN 978-0-521-81405-8 (Cloth)

References

1.
2. Penrose, R. (1969). Gravitational collapse: The role of general relativity. ''Nuovo Cimento Rivista'', Numero Speciale '1', 252-276.
3. Williams, R. K. (1995, May 15). Extracting x rays, Ύ rays, and relativistic e^-e⁺ pairs from supermassive Kerr black holes using the Penrose mechanism. ''Physical Review'', '51'(10), 5387-5427.
4. Williams, R. K. (2004, August 20). Collimated escaping vortical polar e^-e⁺ jets intrinsically produced by rotating black holes and Penrose processes. ''The Astrophysical Journal'', '611', 952-963.
5. Gariel, J.; MacCallum, M. A. H.; Marcilhacy, G.; Santos, N. O. (2007, February 23). Kerr geodesics, the Penrose process and jet collimation by a black hole. Preprint arXiv: gr-qc/0702123v1.
6. Williams, R. K. (2001, October 15). Collimated energy-momentum extraction from rotating black holes in quasars and microquasars using the Penrose mechanism. ''AIP Conference Proceedings'', '586', 448-453.

External links

★ Jets and Binary Systems