The Naked Scientists

The Naked Scientists Forum

Author Topic: Black hole jets  (Read 1510 times)

Offline allan marsh

  • Full Member
  • ***
  • Posts: 91
    • View Profile
Black hole jets
« on: 19/06/2014 22:17:54 »
In images of black holes one sees jets coming out perpendicular to the disc.
1..
What are the jets made of
2
Why do they exit from both sides of the disc
3
They spread out over light years at narrow angles ... What determines the angle of the spread please.


 

Offline PmbPhy

  • Neilep Level Member
  • ******
  • Posts: 2760
  • Thanked: 38 times
    • View Profile
Re: Black hole jets
« Reply #1 on: 20/06/2014 00:14:45 »
Wikipedia explains it as follows
Quote
While it is not known exactly how accretion discs manage to produce jets, they are thought to generate tangled magnetic fields that cause the jets to collimate.

Quote from: allan marsh
1. What are the jets made of
Some sort of matter. I think its a plasma of some sort. Most probably it is whatever falls into the black hole from the accretion disk.

Quote from: allan marsh
2. Why do they exit from both sides of the disc
Symmetry. Whatever the mechanism is there must be a symmetry to it because there is nothing inherently different in one direction from the other.

Quote from: allan marsh
3. They spread out over light years at narrow angles ... What determines the angle of the spread please.
You've got me. Perhaps the Wikipedia page will tell you that.
 

Offline evan_au

  • Neilep Level Member
  • ******
  • Posts: 4113
  • Thanked: 245 times
    • View Profile
Re: Black hole jets
« Reply #2 on: 20/06/2014 12:54:31 »
Quote
1..What are the jets made of
Most of the universe is made of hydrogen (electrons and protons). So we can guess that most of the matter falling into a black hole is Hydrogen. It would be heated to extremely high temperatures in the accretion disk of a black hole, and these extreme energies would produce gamma rays, and could produce other subatomic particles like positrons.

These jets travel very close to the speed of light, so unstable particles like mesons could last much much longer than we experience on Earth.

Quote
3 They spread out over light years at narrow angles

There are a number of theories, often involving magnetic fields in the plasma of an accretion disk, perhaps interacting with the "Frame Dragging" which is predicted by the theory of relativity.

These events are hard to model in a supercomputer - fluid flow simulations like designing an aeroplane or predicting Earth's weather are hard enough, but throw in a conductive plasma, incredible shear forces and turbulence, strong magnetic fields and frame dragging, and it turns into a very difficult problem.

Unfortunately (or fortunately, depending on your perspective), the nearest of these jets is far away, and our telescopes can't get a close look at their structure - for example, to see if it is a steady stream of matter, or if it occurs in bursts like a rapid-fire coronal mass ejection.

For more information, see: http://en.wikipedia.org/wiki/Relativistic_jet#Relativistic_jet
 

Offline allan marsh

  • Full Member
  • ***
  • Posts: 91
    • View Profile
Re: Black hole jets
« Reply #3 on: 22/06/2014 18:33:54 »
The usual orientations in diagrams are edge on view with jets up,and down
However in billions of galaxies one black hole jets MUST point directly at us
Surely we should see this effect... If we can see the light of far galaxies we should see the effect of head on jets
That is unless the jets diverge and form mushroom shapes about the galaxy, returning the plasma to its own galaxy
 

Offline evan_au

  • Neilep Level Member
  • ******
  • Posts: 4113
  • Thanked: 245 times
    • View Profile
Re: Black hole jets
« Reply #4 on: 22/06/2014 21:51:32 »
It is thought that Quasars are produced by jets from galactic black holes, which happen to be pointed in our direction.

The intensity of Quasars can vary significantly on time scales as short as hours, implying that the central source is no larger than our Solar System. This is compatible with a source which is a galactic black hole.

Initially, images of Quasars were observed as point sources, but in some cases a surrounding galaxy has now been observed.

 

The Naked Scientists Forum

Re: Black hole jets
« Reply #4 on: 22/06/2014 21:51:32 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums
 
Login
Login with username, password and session length