A newly discovered effect of general relativity means that rotating black holes should be visible to the current generation of telescopes, say astronomers.
Black holes do strange things to the fabric of space time, particularly if they are rotating. One well known effect is that a rotating black hole drags this fabric with it, intermixing space and time in nearby regions.
Today, Fabrizio Tamburini at the University of Padova in Italy and a few pals say this ought to have a significant effect on light that gets caught up in this process and is then emitted from the disc of accreting matter around a rotating black hole. They say the rotation ought to distort the wave front and phase of this light, while imparting orbital angular momentum to the beam.
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