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Can someone explain why this particle couldn't have been gravitationally accelerated by taking a turn around a super-massive black hole just on the edge of the

Can someone explain why this particle couldn't have been gravitationally accelerated by taking a turn around a super-massive black hole just on the edge of the event horizon? Is there a limit to how much acceleration a black hole can give?

WendyTheWillow 3y ago
The article says there are no known quasars in the area of space where the energy is seemingly from, or at least that’s my interpretation. So yeah it could be from a black hole, just an unknown one. Or it’s from a different region of space than we think, and our math is off.
maxnoe 3y ago
Mass is of a single particle is extremely small (proton has a mass of 1.6e-27 kg), speed is very high and already very close to the speed of light at all but the lowest energies, so gravity "assists" are not really anything with which you can gain energy. These are charged particles (protons and fully ionized heavier nuclei), so electromagnetism is a much more efficient way to reach high energies. All currently proposed mechanisms for cosmic ray acceleration involve turbulent plasmas and shock fronts that reflect particles magnetically, giving them a small bump in energy each time [1] or rotating magnetic fields [2] in sufficiently extreme environments. [1] https://en.wikipedia.org/wiki/Fermi_acceleration https://en.wikipedia.org/wiki/Fermi_acceleration [2] https://en.wikipedia.org/wiki/Centrifugal_acceleration_(astrophysics) https://en.wikipedia.org/wiki/Centrifugal_acceleration_(astr... Gravity just doesn't play a direct role for accelerating charged particles, it's much too weak compared to the electromagnetic force for a charged particle.
- saiya-jin 3y ago
  So, a pulsar would do the trick? How far back do we simulate movement of milky way and all galaxies around to say for sure they come from an 'empty' place? I think our local supercluster look quite a bit different say 1 billion years ago
  - eesmith 3y ago
    The particle is traveling at a whisker under the speed of light. If I read things correctly, it's only a few light-days behind what the light would be after 1 billion years. So what we see should (as we we understand it) look like the conditions where/when it achieved its tremendous speed.
    - saiya-jin 3y ago
      Thank you for the explanation it makes sense (I wonder how much time that particle 'experienced'), apart from that obvious mystery of where it came from
ars 3y ago
That's not how gravitational acceleration works. If the particle accelerates towards black hole it will decelerate when the leaves the black hole. To actually accelerate and keep it, you need a third particle. In a spaceship that third particle is the fuel. In a solar system that third particle is the planets interacting with their sun. My post is telling you what's needed without explaining it at all, please watch some YouTube videos to actually understand it.
- NegativeK 3y ago
  You can extract energy from a rotating black hole via slingshotting around it. But it's not an amount relevant to this discussion.
  - scotty79 3y ago
    Is the amount bounded? Doesn't it get higher the closer the particle gets during the maneuver?
- pixl97 3y ago
  So, I'd say it's a little more complicated than this even. There are orbitals around black holes where particles could maintain stable orbits for long periods of time. Now when you get a complex environment around said black hole with lots matter attempting to infall but not having the correct momentum you will get a lot of interaction between particles of different velocities, hence why we actually see black holes at all. you get matter crashing into each other releasing gamma rays and such. From these interactions alone you can get gravitational particle acceleration. It just gets more complicated from here as you add magnetic field interactions.

WendyTheWillow 3y ago

The article says there are no known quasars in the area of space where the energy is seemingly from, or at least that’s my interpretation. So yeah it could be from a black hole, just an unknown one. Or it’s from a different region of space than we think, and our math is off.

maxnoe 3y ago

Mass is of a single particle is extremely small (proton has a mass of 1.6e-27 kg), speed is very high and already very close to the speed of light at all but the lowest energies, so gravity "assists" are not really anything with which you can gain energy. These are charged particles (protons and fully ionized heavier nuclei), so electromagnetism is a much more efficient way to reach high energies. All currently proposed mechanisms for cosmic ray acceleration involve turbulent plasmas and shock fronts that reflect particles magnetically, giving them a small bump in energy each time [1] or rotating magnetic fields [2] in sufficiently extreme environments. [1] https://en.wikipedia.org/wiki/Fermi_acceleration https://en.wikipedia.org/wiki/Fermi_acceleration [2] https://en.wikipedia.org/wiki/Centrifugal_acceleration_(astrophysics) https://en.wikipedia.org/wiki/Centrifugal_acceleration_(astr... Gravity just doesn't play a direct role for accelerating charged particles, it's much too weak compared to the electromagnetic force for a charged particle.

saiya-jin 3y ago
So, a pulsar would do the trick? How far back do we simulate movement of milky way and all galaxies around to say for sure they come from an 'empty' place? I think our local supercluster look quite a bit different say 1 billion years ago
- eesmith 3y ago
  The particle is traveling at a whisker under the speed of light. If I read things correctly, it's only a few light-days behind what the light would be after 1 billion years. So what we see should (as we we understand it) look like the conditions where/when it achieved its tremendous speed.
  - saiya-jin 3y ago
    Thank you for the explanation it makes sense (I wonder how much time that particle 'experienced'), apart from that obvious mystery of where it came from

ars 3y ago

That's not how gravitational acceleration works. If the particle accelerates towards black hole it will decelerate when the leaves the black hole. To actually accelerate and keep it, you need a third particle. In a spaceship that third particle is the fuel. In a solar system that third particle is the planets interacting with their sun. My post is telling you what's needed without explaining it at all, please watch some YouTube videos to actually understand it.

NegativeK 3y ago
You can extract energy from a rotating black hole via slingshotting around it. But it's not an amount relevant to this discussion.
- scotty79 3y ago
  Is the amount bounded? Doesn't it get higher the closer the particle gets during the maneuver?
pixl97 3y ago
So, I'd say it's a little more complicated than this even. There are orbitals around black holes where particles could maintain stable orbits for long periods of time. Now when you get a complex environment around said black hole with lots matter attempting to infall but not having the correct momentum you will get a lot of interaction between particles of different velocities, hence why we actually see black holes at all. you get matter crashing into each other releasing gamma rays and such. From these interactions alone you can get gravitational particle acceleration. It just gets more complicated from here as you add magnetic field interactions.