Twisting of light around rotating black holes

TL;DR

This paper predicts a new relativistic effect where light passing near rotating black holes acquires orbital angular momentum, which can potentially be observed with current telescopes, providing a direct test of black hole rotation.

Contribution

It introduces the concept that rotating black holes induce orbital angular momentum in nearby light, supported by numerical simulations of null geodesics in Kerr spacetime.

Findings

Light near Kerr black holes gains orbital angular momentum.

Numerical simulations confirm phase change and wavefront warping.

Potential for observational detection with existing telescopes.

Abstract

Kerr black holes are among the most intriguing predictions of Einstein's general relativity theory. These rotating massive astrophysical objects drag and intermix their surrounding space and time, deflecting and phase-modifying light emitted nearby them. We have found that this leads to a new relativistic effect that imposes orbital angular momentum onto such light. Numerical experiments, based on the integration of the null geodesic equations of light from orbiting point-like sources in the Kerr black hole equatorial plane to an asymptotic observer, indeed identify the phase change and wavefront warping and predict the associated light-beam orbital angular momentum spectra. Setting up the best existing telescopes properly, it should be possible to detect and measure this twisted light, thus allowing a direct observational demonstration of the existence of rotating black holes. Since non-rotating objects are more an exception than a rule in the Universe, our findings are of fundamental importance.