**Publication date:** n/a 1976

**Abstract:**

The authors investigate the motion of a test particle in the Kerr metric

using Boyer-Lindquist coordinates, extending the results of de Felice

and Calvani (FC) (1972) to cases not covered by them, and also

considering further details concerning, in particular, photons moving

along the principal null congruences. Whereas FC considered only

nonnegative values of L = q + l-squared, here negative values are

treated. Curves are drawn showing l-aquared as a function of Theta for a

fixed positive Gamma and typical values of L, demonstrating the

oscillatory nature of the latitudinal motion. Four families of photon

world lines with constant latitudes are found. A graph of L/a-squared

versus x for a fixed l/a is drawn from calculations, which is used to

analyze the r-motions of photons.

**Authors:**

Bicak, J.; Stuchlik, Z.;