Turning points of massive particles in Schwarzschild geometry
arXiv:0902.3808
Abstract
The stable geodesics in Schwarzschild geometry can not approach the center closer than the radius of the photon sphere, 3/2 times the Schwarzschild radius. In other words, massive particles moving along geodesics that cross the photon sphere do not escape, they fall into the black hole.
2 pages, 1 figure