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Author Topic: Are relativistic jets conical?  (Read 1354 times)

Offline jeffreyH

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Are relativistic jets conical?
« on: 02/10/2013 15:43:58 »
Do these jets always exhibit a conical form?


 

Offline Supercryptid

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Re: Are relativistic jets conical?
« Reply #1 on: 02/10/2013 20:28:16 »
Probably to some approximation. Since they are made of gas, they will tend to expand in a vacuum over time. This will make the "end" of the jet larger in size than its "base".
 

Offline Phractality

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Re: Are relativistic jets conical?
« Reply #2 on: 04/10/2013 05:38:44 »
The jets spew from opposite poles of a rotating star or black hole's axis. These objects tend to precess rapidly, so the axis describes a conical path. The jets spiral outward along that cone. Similarly, a powerful light beam may be emitted from the objects axis. If Earth happens to be located on the cone (adjusting for the light speed delay), the object will appear as a pulsar. Some pulsars pulse every few milliseconds because the object is precessing that fast.
 

Offline jeffreyH

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Re: Are relativistic jets conical?
« Reply #3 on: 04/10/2013 07:00:05 »
It's interesting that the jets spiral as that is what I was expecting to happen. I initially thought this would be outside the event horizon but now I believe it to be from within.
 

Offline evan_au

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Re: Are relativistic jets conical?
« Reply #4 on: 04/10/2013 11:19:01 »
Active galaxies often display radio lobes created by relativistic jets. Cygnus A is a galaxy with two conical relativistic streams which travel far beyond the galaxy before they slow and spread out in the intergalactic medium. These jets originate in a galactic black hole, see animation & picture at: http://www.cv.nrao.edu/~abridle/dragnparts.htm

Our galaxy's black hole is currently rather passive, but has been more active in the past. This has blasted some material out along the axis, but because it is intermittent, it has slowed down and spread out as soon as it leaves the plane of the galaxy. See picture at http://www.skyandtelescope.com/community/skyblog/newsblog/Galactic-Bubbles-Spark-Debate-186963791.html

There are cases where the relativistic jets have a sudden bend (symmetrical on both sides of a galaxy). Could this be due to the merger of two galactic black holes, which changes the axis of rotation, and this the direction of the relativistic jets?

Pulsars
The common theory about pulsars are that they are spinning neutron stars.
Like a black hole, nearby gas and dust will form an accretion disk around a neutron star, and magnetohydrodynamic forces in the accretion disk may result in directing matter in high-speed jets out along the axis of rotation.

There is a movie of the Vela Pulsar at X-Ray wavelengths here: http://en.wikipedia.org/wiki/Pulsar
In this case, the axial jet seems to have a steady axis (not precessing). The matter is ejected along the axis at high speed until it hits the interstellar medium, slows and spreads out. The axial jets are not the source of the pulsing light, since in this case, we are not seeing the jets end-on.

Unlike a black hole, the neutron star does not have an event horizon, so an event horizon is not necessary to produce high-speed jets.
 

Offline jeffreyH

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Re: Are relativistic jets conical?
« Reply #5 on: 04/10/2013 21:16:56 »
Active galaxies often display radio lobes created by relativistic jets. Cygnus A is a galaxy with two conical relativistic streams which travel far beyond the galaxy before they slow and spread out in the intergalactic medium. These jets originate in a galactic black hole, see animation & picture at: http://www.cv.nrao.edu/~abridle/dragnparts.htm

Our galaxy's black hole is currently rather passive, but has been more active in the past. This has blasted some material out along the axis, but because it is intermittent, it has slowed down and spread out as soon as it leaves the plane of the galaxy. See picture at http://www.skyandtelescope.com/community/skyblog/newsblog/Galactic-Bubbles-Spark-Debate-186963791.html

There are cases where the relativistic jets have a sudden bend (symmetrical on both sides of a galaxy). Could this be due to the merger of two galactic black holes, which changes the axis of rotation, and this the direction of the relativistic jets?

Pulsars
The common theory about pulsars are that they are spinning neutron stars.
Like a black hole, nearby gas and dust will form an accretion disk around a neutron star, and magnetohydrodynamic forces in the accretion disk may result in directing matter in high-speed jets out along the axis of rotation.

There is a movie of the Vela Pulsar at X-Ray wavelengths here: http://en.wikipedia.org/wiki/Pulsar
In this case, the axial jet seems to have a steady axis (not precessing). The matter is ejected along the axis at high speed until it hits the interstellar medium, slows and spreads out. The axial jets are not the source of the pulsing light, since in this case, we are not seeing the jets end-on.

Unlike a black hole, the neutron star does not have an event horizon, so an event horizon is not necessary to produce high-speed jets.

Thanks for the info, especially on the neutron stars. I would imagine that it is the electromagnetic field, rather than the gravitational field, that moves the matter to the poles. What I am unsure about is whether or not this is the mechanism that propels the jets. I will be looking at the links you posted.
 

Offline jeffreyH

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Re: Are relativistic jets conical?
« Reply #6 on: 04/10/2013 22:04:01 »
There is something else that runs counter to my original thinking. It is the fact that elliptical rather than spiral galaxies are more likely to exhibit jets in the galactic core. This actually might be a clue to what is actually happening and which force creates the effect.
 

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Re: Are relativistic jets conical?
« Reply #6 on: 04/10/2013 22:04:01 »

 

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