An astrophysical jet is an
astronomical phenomenon where outflows of
ionised matter are emitted as an extended beam along the
axis of rotation. When this greatly accelerated matter in the beam approaches the
speed of light
The speed of light in vacuum, commonly denoted , is a universal physical constant that is important in many areas of physics. The speed of light is exactly equal to ). According to the special theory of relativity, is the upper limit fo ...
, astrophysical jets become relativistic jets as they show effects from
special relativity
In physics, the special theory of relativity, or special relativity for short, is a scientific theory regarding the relationship between space and time. In Albert Einstein's original treatment, the theory is based on two postulates:
# The law ...
.
The formation and powering of astrophysical jets are highly complex phenomena that are associated with many types of high-energy astronomical sources. They likely arise from dynamic interactions within
accretion disks, whose active processes are commonly connected with compact central objects such as
black hole
A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can defo ...
s,
neutron star
A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. w ...
s or
pulsar
A pulsar (from ''pulsating radio source'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be observed only when a beam of emission is pointing toward E ...
s. One explanation is that tangled
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and t ...
s are organised to aim two diametrically opposing beams away from the central source by angles only several degrees wide Jets may also be influenced by a
general relativity
General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. ...
effect known as
frame-dragging.
Most of the largest and most active jets are created by
supermassive black hole
A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions of times the mass of the Sun (). Black holes are a class of astronomical obj ...
s (SMBH) in the centre of
active galaxies such as
quasar
A quasar is an extremely luminous active galactic nucleus (AGN). It is pronounced , and sometimes known as a quasi-stellar object, abbreviated QSO. This emission from a galaxy nucleus is powered by a supermassive black hole with a mass rangin ...
s and
radio galaxies or within galaxy clusters. Such jets can exceed millions of
parsec
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, a ...
s in length.
Other astronomical objects that contain 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
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
.
Bipolar outflows may also be associated with
protostars, or with evolved
post-AGB stars,
planetary nebulae and
bipolar nebulae.
Relativistic jets
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
quasar
A quasar is an extremely luminous active galactic nucleus (AGN). It is pronounced , and sometimes known as a quasi-stellar object, abbreviated QSO. This emission from a galaxy nucleus is powered by a supermassive black hole with a mass rangin ...
s, and also by galactic
stellar black holes,
neutron star
A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. w ...
s or
pulsar
A pulsar (from ''pulsating radio source'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be observed only when a beam of emission is pointing toward E ...
s. Beam lengths may extend between several thousand, hundreds of thousands or millions of parsecs.
Jet velocities when approaching the speed of light show significant effects of the
special theory of relativity
In physics, the special theory of relativity, or special relativity for short, is a scientific theory regarding the relationship between space and time. In Albert Einstein's original treatment, the theory is based on two postulates:
# The laws o ...
; for example,
relativistic beaming that changes the apparent beam brightness.
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 hole
A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can defo ...
s. These SMBH systems are often called
microquasars and show a large range of velocities.
SS 433 jet, for example, has a mean velocity of 0.26
c. Relativistic jet formation may also explain observed
gamma-ray bursts.
Mechanisms behind the composition of jets remain uncertain, though some studies favour models where jets are composed of an electrically neutral mixture of
nuclei,
electron
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary partic ...
s, and
positron
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. It has an electric charge of +1 '' e'', a spin of 1/2 (the same as the electron), and the same mass as an electron. When a positron collide ...
s, while others are consistent with jets composed of positron–electron plasma.
[Electron–positron Jets Associated with Quasar 3C 279](_blank)
/ref> 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 hole
A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can defo ...
s. However, the frequency of high-energy astrophysical sources with jets suggest 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. 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. Here energy is extracted from a rotating black hole by frame dragging
Frame-dragging is an effect on spacetime, predicted by Albert Einstein's general theory of relativity, that is due to non-static stationary distributions of mass–energy. A stationary field is one that is in a steady state, but the masses cau ...
, which was later theoretically proven to be able to extract relativistic particle energy and momentum, and subsequently shown to be a possible mechanism for jet formation. This effect includes using general relativistic gravitomagnetism.
Relativistic jets from neutron stars
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
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked ey ...
, and whose velocity is estimated at 80% the speed of light (0.8''c''). X-ray observations have been obtained but there is no detected radio signature nor accretion disk. Initially, this pulsar was presumed to be rapidly spinning but later measurements indicate the spin rate is only 15.9 Hz.[
] 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
File:Opo0113i.jpg, Illustration of the dynamics of a proplyd, including a jet
File:NGC 5128.jpg, Centaurus A in x-rays showing the relativistic jet
File:Onde-radioM87.jpg, The M87 jet seen by the Very Large Array
The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~ west of Socorro. The VLA comprises twent ...
in radio frequency
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the uppe ...
(the viewing field is larger and rotated with respect to the above image.)
File:HST-3C66B-jet-O5BQ06010.gif, Hubble Legacy Archive Near- UV image of the relativistic jet in 3C 66B
File:hs-2015-19-a-small web.jpg, Galaxy NGC 3862
NGC 3862 is an elliptical galaxy located 300 million light-years away in the constellation Leo (constellation), Leo. Discovered by astronomer William Herschel on April 27, 1785, NGC 3862 is an outlying member of the Leo Cluster.
The galaxy is cl ...
, an extragalactic jet of material moving at nearly the speed of light can be seen at the three o'clock position.
File:Hubble Sees the Force Awakening in a Newborn Star (23807356641).jpg, Some of the jets in HH 24-26
HH 24-26 is a molecular cloud and star-forming region containing the Herbig-Haro objects HH 24, HH 25 and HH 26. This region contains the highest concentration of astrophysical jets known anywhere in the sky. The molecular cloud is located abo ...
, which contains the highest concentration of jets known anywhere in the sky
See also
* Accretion disk
* Bipolar outflow
* Blandford–Znajek process
* CGCG 049-033
CGCG 049-033 is an elliptical galaxy, located some 680 million light-years from Earth, in the constellation of Serpens. It is the central galaxy (BCG) of the galaxy cluster Abell 2040.
CGCG 049-033 is known for having the longest galactic jet ...
, elliptical galaxy located 600 million light-years from Earth, known for having the longest galactic jet discovered
* List of plasma physics articles
References
External links
NASA – Ask an Astrophysicist: Black Hole Bipolar Jets
* {{Cite arXiv , eprint=astro-ph/0107228v1 , last1=Blandford , first1=Roger , title=Compact Objects and Accretion Disks , last2=Agol , first2=Eric , last3=Broderick , first3=Avery , last4=Heyl , first4=Jeremy , last5=Koopmans , first5=Leon , last6=Lee , first6=Hee-Won , year=2001
Hubble Video Shows Shock Collision inside Black Hole Jet
Article
Jet
Jet, Jets, or The Jet(s) may refer to:
Aerospace
* Jet aircraft, an aircraft propelled by jet engines
** Jet airliner
** Jet engine
** Jet fuel
* Jet Airways, an Indian airline
* Wind Jet (ICAO: JET), an Italian airline
* Journey to Enceladus a ...
Plasma physics
Black holes
Jet, Astrophysical