Astrophysical jet

The starburst galaxy Centaurus A, with its plasma jets extending over a million light years, is considered as the closest active radio galaxy to Earth. The 870-micron submillimetre data, from LABOCA on APEX, are shown in orange. X-ray data from the Chandra X-ray Observatory are shown in blue. Visible light data from the Wide Field Imager (WFI) on the MPG/ESO 2.2 m telescope located at La Silla, Chile, show the background stars and the galaxy's characteristic dust lane in close to "true colour".

An astrophysical jet is an astronomical phenomenon where ionised matter is expelled at high velocity from an astronomical object, in a pair of narrow streams aligned with the object's axis of rotation. ^[1] When the matter in the beam approaches the speed of light, astrophysical jets become relativistic jets as they show effects from special relativity.

Astrophysical jets are associated with many types of high-energy astronomical sources, such as black holes, neutron stars and pulsars. Their causes are not yet fully understood, but they are believed to arise from dynamic interactions within accretion disks. One explanation is that as an accretion disk spins, it generates a rotating, tangled magnetic field which concentrates material from the disk into the jets and then drives it away from the central object. ^[2] Jets may also be influenced by a general relativity effect known as frame-dragging. ^[3]

Most of the largest and most active jets are created by supermassive black holes (SMBH) in the centre of active galaxies such as quasars and radio galaxies or within galaxy clusters. ^[4] Such jets can exceed millions of parsecs in length. ^[2] Other astronomical objects that produce, or are caused by, jets include cataclysmic variable stars, X-ray binaries and gamma-ray bursts (GRB). Jets on a much smaller scale (~parsecs) may be found in star forming regions, including T Tauri stars and Herbig–Haro objects; these objects are partially formed by the interaction of jets with the interstellar medium. Bipolar outflows may also be associated with protostars, ^[5] or with evolved post-AGB stars, planetary nebulae and bipolar nebulae.

Relativistic jets

Elliptical galaxy M87 emitting a relativistic jet, as seen by the Hubble Space Telescope

Relativistic jets are beams of ionised matter accelerated close to the speed of light. Most have been observationally associated with central black holes of some active galaxies, radio galaxies or quasars, and also by galactic stellar black holes, neutron stars or pulsars. Beam lengths may extend between several thousand, ^[6] hundreds of thousands ^[7] or millions of parsecs. ^[2] Jet velocities when approaching the speed of light show significant effects of the special theory of relativity; for example, relativistic beaming that changes the apparent beam brightness. ^[8]

Massive central black holes in galaxies have the most powerful jets, but their structure and behaviours are similar to those of smaller galactic neutron stars and black holes. These SMBH systems are often called microquasars and show a large range of velocities. SS 433 jet, for example, has a mean velocity of 0.26c. ^[9] Relativistic jet formation may also explain observed gamma-ray bursts, which have the most relativistic jets known, being ultrarelativistic. ^[10]

Mechanisms behind the composition of jets remain uncertain, ^[11] though some studies favour models where jets are composed of an electrically neutral mixture of nuclei, electrons, and positrons, while others are consistent with jets composed of positron–electron plasma. ^{[12] [13] [14]} Trace nuclei swept up in a relativistic positron–electron jet would be expected to have extremely high energy, as these heavier nuclei should attain velocity equal to the positron and electron velocity.

Rotation as possible energy source

Because of the enormous amount of energy needed to launch a relativistic jet, some jets are possibly powered by spinning black holes. However, the frequency of high-energy astrophysical sources with jets suggests combinations of different mechanisms indirectly identified with the energy within the associated accretion disk and X-ray emissions from the generating source. Two early theories have been used to explain how energy can be transferred from a black hole into an astrophysical jet:

• Blandford–Znajek process. ^[15] This theory explains the extraction of energy from magnetic fields around an accretion disk, which are dragged and twisted by the spin of the black hole. Relativistic material is then feasibly launched by the tightening of the field lines.
• Penrose mechanism. ^[16] Here energy is extracted from a rotating black hole by frame dragging, which was later theoretically proven by Reva Kay Williams to be able to extract relativistic particle energy and momentum, ^[17] and subsequently shown to be a possible mechanism for jet formation. ^[18] This effect includes using general relativistic gravitomagnetism.

Relativistic jets from neutron stars

The pulsar IGR J11014-6103 with supernova remnant origin, nebula and jet

Jets may also be observed from spinning neutron stars. An example is pulsar IGR J11014-6103, which has the largest jet so far observed in the Milky Way, and whose velocity is estimated at 80% the speed of light (0.8c). X-ray observations have been obtained, but there is no detected radio signature nor accretion disk. ^{[19] [20]} Initially, this pulsar was presumed to be rapidly spinning, but later measurements indicate the spin rate is only 15.9 Hz. ^{[21] [22]} Such a slow spin rate and lack of accretion material suggest the jet is neither rotation nor accretion powered, though it appears aligned with the pulsar rotation axis and perpendicular to the pulsar's true motion.

Other images

• 
  Illustration of the dynamics of a proplyd, including a jet
• 
  Centaurus A in x-rays showing the relativistic jet
• 
  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.)
• 
  Hubble Legacy Archive Near-UV image of the relativistic jet in 3C 66B
• 
  Galaxy NGC 3862, an extragalactic jet of material moving at nearly the speed of light can be seen at the three o'clock position.
• 
  Some of the jets in HH 24-26, which contains the highest concentration of jets known anywhere in the sky

See also

• disk wind slower wide-angle outflow, often occurring together with a jet
• Accretion disk
• Bipolar outflow
• Blandford–Znajek process
• Herbig–Haro object
• Penrose process
• CGCG 049-033, elliptical galaxy located 600 million light-years from Earth, known for having the longest galactic jet discovered
• Gamma-ray burst
• Solar jet

References

1. Beall, J. H. (2015). "A Review of Astrophysical Jets" (PDF). Proceedings of Science : 58. Bibcode:2015mbhe.confE..58B. doi: 10.22323/1.246.0058 . Retrieved 19 February 2017.
2. Kundt, W. (2014). "A Uniform Description of All the Astrophysical Jets" (PDF). Proceedings of Science : 58. Bibcode:2015mbhe.confE..58B. doi: 10.22323/1.246.0058 . Retrieved 19 February 2017.
3. Miller-Jones, James (April 2019). "A rapidly changing jet orientation in the stellar-mass black-hole system V404 Cygni" (PDF). Nature. 569 (7756): 374–377. arXiv: 1906.05400 . Bibcode:2019Natur.569..374M. doi:10.1038/s41586-019-1152-0. PMID   31036949. S2CID   139106116.
4. Beall, J. H (2014). "A review of Astrophysical Jets". Acta Polytechnica CTU Proceedings. 1 (1): 259–264. Bibcode:2014mbhe.conf..259B. doi: 10.14311/APP.2014.01.0259 .
5. "Star sheds via reverse whirlpool". Astronomy.com. 27 December 2007. Retrieved 26 May 2015.
6. Biretta, J. (6 Jan 1999). "Hubble Detects Faster-Than-Light Motion in Galaxy M87".
7. "Evidence for Ultra-Energetic Particles in Jet from Black Hole". Yale University – Office of Public Affairs. 20 June 2006. Archived from the original on 2008-05-13.
8. Semenov, V.; Dyadechkin, S.; Punsly, B. (2004). "Simulations of Jets Driven by Black Hole Rotation". Science . 305 (5686): 978–980. arXiv: astro-ph/0408371 . Bibcode:2004Sci...305..978S. doi:10.1126/science.1100638. PMID   15310894. S2CID   1590734.
9. Blundell, Katherine (December 2008). "Jet Velocity in SS 433: Its Anticorrelation with Precession-Cone Angle and Dependence on Orbital Phase". The Astrophysical Journal. 622 (2): 129. arXiv: astro-ph/0410457 . doi: 10.1086/429663 . Retrieved 15 January 2021.
10. Dereli-Bégué, Hüsne; Pe’er, Asaf; Ryde, Felix; Oates, Samantha R.; Zhang, Bing; Dainotti, Maria G. (2022-09-24). "A wind environment and Lorentz factors of tens explain gamma-ray bursts X-ray plateau". Nature Communications. 13 (1): 5611. arXiv: 2207.11066 . Bibcode:2022NatCo..13.5611D. doi:10.1038/s41467-022-32881-1. ISSN   2041-1723. PMC   9509382 . PMID   36153328.
11. Georganopoulos, M.; Kazanas, D.; Perlman, E.; Stecker, F. W. (2005). "Bulk Comptonization of the Cosmic Microwave Background by Extragalactic Jets as a Probe of Their Matter Content". The Astrophysical Journal . 625 (2): 656–666. arXiv: astro-ph/0502201 . Bibcode:2005ApJ...625..656G. doi:10.1086/429558. S2CID   39743397.
12. Hirotani, K.; Iguchi, S.; Kimura, M.; Wajima, K. (2000). "Pair Plasma Dominance in the Parsec-Scale Relativistic Jet of 3C 345". The Astrophysical Journal . 545 (1): 100–106. arXiv: astro-ph/0005394 . Bibcode:2000ApJ...545..100H. doi:10.1086/317769. S2CID   17274015.
13. Electron–positron Jets Associated with Quasar 3C 279
14. Naeye, R.; Gutro, R. (2008-01-09). "Vast Cloud of Antimatter Traced to Binary Stars". NASA.
15. Blandford, R. D.; Znajek, R. L. (1977). "Electromagnetic extraction of energy from Kerr black holes". Monthly Notices of the Royal Astronomical Society . 179 (3): 433. arXiv: astro-ph/0506302 . Bibcode:1977MNRAS.179..433B. doi: 10.1093/mnras/179.3.433 .
16. Penrose, R. (1969). "Gravitational Collapse: The Role of General Relativity". Rivista del Nuovo Cimento . 1: 252–276. Bibcode:1969NCimR...1..252P. Reprinted in: Penrose, R. (2002). ""Golden Oldie": Gravitational Collapse: The Role of General Relativity". General Relativity and Gravitation . 34 (7): 1141–1165. Bibcode:2002GReGr..34.1141P. doi:10.1023/A:1016578408204. S2CID   117459073.
17. Williams, R. K. (1995). "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. Bibcode:1995PhRvD..51.5387W. doi:10.1103/PhysRevD.51.5387. PMID   10018300.
18. Williams, R. K. (2004). "Collimated Escaping Vortical Polar e−e+Jets Intrinsically Produced by Rotating Black Holes and Penrose Processes". The Astrophysical Journal . 611 (2): 952–963. arXiv: astro-ph/0404135 . Bibcode:2004ApJ...611..952W. doi:10.1086/422304. S2CID   1350543.
19. "Chandra :: Photo Album :: IGR J11014-6103 :: June 28, 2012".
20. Pavan, L.; et al. (2015). "A closer view of the IGR J11014-6103 outflows". Astronomy & Astrophysics. 591: A91. arXiv: 1511.01944 . Bibcode:2016A&A...591A..91P. doi:10.1051/0004-6361/201527703. S2CID   59522014.
21. Pavan, L.; et al. (2014). "The long helical jet of the Lighthouse nebula, IGR J11014-6103" (PDF). Astronomy & Astrophysics . 562 (562): A122. arXiv: 1309.6792 . Bibcode:2014A&A...562A.122P. doi:10.1051/0004-6361/201322588. S2CID   118845324. Long helical jet of Lighthouse nebula page 7
22. Halpern, J. P.; et al. (2014). "Discovery of X-ray Pulsations from the INTEGRAL Source IGR J11014-6103". The Astrophysical Journal . 795 (2): L27. arXiv: 1410.2332 . Bibcode:2014ApJ...795L..27H. doi:10.1088/2041-8205/795/2/L27. S2CID   118637856.

External links

• NASA – Ask an Astrophysicist: Black Hole Bipolar Jets
• SPACE.com – Twisted Physics: How Black Holes Spout Off
• Blandford, Roger; Agol, Eric; Broderick, Avery; Heyl, Jeremy; Koopmans, Leon; Lee, Hee-Won (2001). "Compact Objects and Accretion Disks". arXiv: astro-ph/0107228v1 .
• Hubble Video Shows Shock Collision inside Black Hole Jet (Article)