Why does gravitational lensing produce four copies of the star and not a whole circle of copies? I would have expected the light to bend evenly around the intermediate star, giving a halo-like effect.
A favourite human made example seems to be the base of a wine glass, that manages similar levels of awfulness, see third picture here for how the same basic shape can make different images of the same source: http://inspirehep.net/record/850223/plots#
https://physics.stackexchange.com/questions/14056/how-does-g...
While stars can do gravitational lensing, due to both the fact that we can see more galaxies, and they have larger mass, it is easier for it to happen with galaxies.