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April 21, 2011

Black holes could be detectable with existing telescopes because rotating black holes twist light

MIT Technology Review - New research indicates that a rotating black holes should be visible. "It should be possible to detect and measure this twisted light," say Tamburini and co.
So where might we find such a black hole? One candidate is the supermassive black hole at the centre of the Milky Way. Tamburini and pals have simulated the way this object ought to twist the light it emits as it rotates and say it could be detected today by the world's best telescopes.

In principle, this kind of observation should be possible tonight, provided the scopes are kitted out with right kind of gear. And since the first observation of a rotating black hole would be a useful thing to have on an astronomical CV, it may not be long before we see the results of just this kind of observation.

Arxiv - Twisting of light around rotating black holes




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.

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