Also fascinating is that celestial bodies that get duplicated by lensing always produce an odd number 2n+1 of images, n of which are inverted and n+1 of which are upright. I won't pretend to understand why this is.<p><a href="https://en.m.wikipedia.org/wiki/Odd_number_theorem" rel="nofollow">https://en.m.wikipedia.org/wiki/Odd_number_theorem</a>
See also: Einstein Ring [0], where a light source passes 'through' a strong gravitational source which refocuses the light spreading out, and the Einstein Cross [1], similar, but where the light source (a quasar) passes a gravitational source and shows up as four points of light "due to the elongated shape of the lensing galaxy and the quasar being off-centre"<p>[0] <a href="https://en.wikipedia.org/wiki/Einstein_ring" rel="nofollow">https://en.wikipedia.org/wiki/Einstein_ring</a><p>[1] <a href="https://en.wikipedia.org/wiki/Einstein_Cross" rel="nofollow">https://en.wikipedia.org/wiki/Einstein_Cross</a>