Very interesting questions, not that I have an answer, lol. But I saw something a while back about Near Earth Objects which escape Earth’s orbit because they never really settle into a stable Earth orbit to begin with. I got the impression they can “orbit” for hundreds of years before conditions are just right and they escape. Perhaps something similar can occur with photons in orbit around a black hole?You're probably thinking of quasi-satellites, bodies in horseshoe orbits or tadpole orbits and the like.
Bear in mind that those are examples involving three-body systems: The Sun, the Earth orbiting the Sun, and a much smaller, third body (asteroid, etc.) interacting with the Earth while, essentially, in orbit around the Sun. That would not be applicable to a scenario involving just a single primary (the Black Hole) and photons.
Again: I'm not denying the validity or at least the plausibility of this article - just saying that when attempting to apply principles of Classical Celestial Mechanics to the described scenario (which the article suggests we should do), I fail.
I can only suspect that "weird science" (i.e., Quantum Mechanical effects and/or Relativistic effects) are involved.
Regards,
Correct, that's right, they're called quasi-satellites. Here's the article I was referring to: ->
http://theconversation.com/earths-got-a-new-moon-heres-what-to-expect-132554. Scanning through it confirms just how bad my memory is; nothing about the article suggests these orbits persist for hundreds of years. That's why it's best for me to say as little about something I casually read, even if recently. *Sigh*... I knew this. When will I ever learn? :-(