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Q & A: Dougnut shaped gravitational lens?

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Most recent answer: 08/07/2010
I have been reading about gravitational lensing. All the models I have seen discuss light going around the outside of some gravitational source, like a black hole or something. Would it act more like a traditional lens if passing through the middle a source that was more donut shaped, instead of around a ball type shape? If so, could somethig like this be done experementally?
- Michael French
Napavine WA
Dear Michael,
First of all gravitational lenses are not like the reading glasses you buy at WalMart.  Ordinary optical lenses focus a point source into a point image.  Gravitational lenses focus a point source into a circular line image.  Sometimes you see only a small arc of the circle depending on the relative positions of the source and lens.   As to whether or not a doughnut shaped lens would work,  I haven't worked it out in detail but I suspect the answer is no.  Could one perform an experiment?   In principle yes, but there are not too many doughnut shaped galaxies out there.
I presume you have read the Wiki article:


(published on 08/07/2010)

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