# Light orbiting BH

1. Aug 4, 2004

### 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?

2. Aug 4, 2004

### 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.

3. Aug 4, 2004

### turin

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