How many Einstein rings have been found to date, i mean galaxies lensed by gravity?
So many, I think, that I seriously doubt anyone has bothered to count them.
Gravitational lensing is a relatively rare phenomenon, but, several hundred candidate lensing events have been identified to date. The OGLE [Optical Gravitational Lensing Experiment] project has probably catalogued the majority of candidate events identified to date. See http://ogle.astrouw.edu.pl/ for further details.
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