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?
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
[2] 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.
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.
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.
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.
But it's not an amount relevant to this discussion.
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.