Photon surface

Photon sphere (definition):A photon sphere of a static spherically symmetric metric is a timelike hypersurface { r = r p s } {displaystyle {r=r_{ps}}} if the deflection angle of a light ray with the closest distance of approach r o {displaystyle r_{o}} diverges as r o → r p s . {displaystyle r_{o} ightarrow r_{ps}.} Photon sphere (definition):A photon sphere of a static spherically symmetric metric is a timelike hypersurface { r = r p s } {displaystyle {r=r_{ps}}} if the deflection angle of a light ray with the closest distance of approach r o {displaystyle r_{o}} diverges as r o → r p s . {displaystyle r_{o} ightarrow r_{ps}.}