Radius of a photon's circular orbit around a mass

[birulami]

What is the radius of a photon's circular orbit around a mass M? My guess would be the Scharzschild radius. Is that true?

 

[WannabeNewton]

http://en.wikipedia.org/wiki/Photon_sphere

 

[Bill_K]

For Kerr, the Wikipedia article only mentions the two (co-rotating and counter-rotating) circular equatorial photon orbits. Does Kerr have closed non-equatorial photon orbits? (If so, they would presumably be noncircular.)

 

[WannabeNewton]

Bill you may find these two pdfs of use in answering that question:
http://arxiv.org/pdf/1210.2486v1.pdf
http://www.physics.nus.edu.sg/~phyteoe/kerr/paper.pdf

 

[Bill_K]

Wow, that's very interesting! Thanks