Since gravitational lensing occurs with large things such as galaxies, could black holes serve the same function? If, near the event horizon with it's high gravitational gradient, would a sharp focus of light rays occur at certain distances from the event horizon? Too far away and the gradient decreases. Too close to the black hole and the information is lost, so a precise distance vs. gravitational gradient point might give a clear image to a distant observer from something far away from it.  Any observation would almost certainly be positioned at an angle to the normal lensed image shallow angle caused by a galaxy or other large object. This angle could be quite high, and only be seen momentarily as the perspectives shifts between the imaged object, the black hole focus point, and the observer, and might explain some anomalies such as gamma ray bursters. It seems a spinning black hole with it's frame dragging would make a sweep of any deflected rays, as in the gamma ray burster idea, and a stationary hole might provide a longer view of lensed rays. Of course this would have to be a free floating black hole for the idea to work.

Edited April 16, 20214 yr by hoola

1 hour ago, hoola said:

Since gravitational lensing occurs with large things such as galaxies, could black holes serve the same function? If, near the event horizon with it's high gravitational gradient, would a sharp focus of light rays occur at certain distances from the event horizon? Too far away and the gradient decreases. Too close to the black hole and the information is lost, so a precise distance vs. gravitational gradient point might give a clear image to a distant observer from something far away from it.  Any observation would almost certainly be positioned at an angle to the normal lensed image shallow angle caused by a galaxy or other large object. This angle could be quite high, and only be seen momentarily as the perspectives shifts between the imaged object, the black hole focus point, and the observer, and might explain some anomalies such as gamma ray bursters. It seems a spinning black hole with it's frame dragging would make a sweep of any deflected rays, as in the gamma ray burster idea, and a stationary hole might provide a longer view of lensed rays. Of course this would have to be a free floating black hole for the idea to work.

Anything with mass, [including Dark Matter]  that creates spacetime curvature will cause gravitational lensing when in the appropriate positions.