light orbiting BH

[turin]

I just wanted a quick affirmation. Can light orbit a black hole? That is, can light remain between two well-defined distances from the event horizon (or at a single well-defined distance, which I am leaning towards) indefinitely?

[DW]

For a Schwarzschild hole it can orbit at the photon sphere r_{ps} which is at
r_{ps} = \frac{3GM}{c^{2}}.
It is an unstable orbit though.

[turin]

Thanks, DW. That's exactly what I was looking for.