Applications of Geometrical Optics to the Kerr Metric. Analytical Results

Abstract

Numerical integrations are performed to investigate the effects of a strong Kerr gravitational field on optical images. In addition to the well-known intensification due to gravitational focusing, the distortion and orientation of various images, and the rotation of the polarization plane, are obtained in terms of the source position. These effects are analyzed from the point of view of (a) a distant observer looking at a source in a close orbit around a Kerr black hole, and (b) a close observer looking at the distant universe. The rotation of the black hole is found to introduce interesting features which are absent in a spherical field.