Light's Bending Angle in the Equatorial Plane of a Kerr Black Hole

We present here a detailed derivation of an explicit spin-dependent expression for the bending angle of light as it traverses in the equatorial plane of a spinning black hole. We show that the deflection produced in the presence of the black hole angular momentum explicitly depends on whether the mo...

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Bibliographic Details
Published in:arXiv.org 2009-07
Main Authors: Iyer, Savitri V, Hansen, Edward C
Format: Article
Language:English
Subjects:
Angular momentum
Axes of rotation
Gravitational lenses
Retrograde orbits
Winding
Online Access:Get full text
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Summary:We present here a detailed derivation of an explicit spin-dependent expression for the bending angle of light as it traverses in the equatorial plane of a spinning black hole. We show that the deflection produced in the presence of the black hole angular momentum explicitly depends on whether the motion of the light ray is in the direction, or opposite to the spin. Compared to the zero-spin Schwarzschild case, the bending angle is greater for direct orbits, and {\em smaller} for retrograde orbits, confirming our physical intuition about the loss of left-right symmetry from a lensing perspective. In addition, we show that for higher spins, the effect is more pronounced resulting in tighter winding of direct orbits with respect to the axis of rotation, and a higher degree of unwinding of retro orbits. A direct consequence of this effect is a shift in image positions in strong gravitational lensing.
ISSN:2331-8422
DOI:10.48550/arxiv.0907.5352