There is a picture in the December Sci. Am. of a galaxy producing a
gravitational lens effect on a quasar and it shows the same quasar
appearing above, below, to the right and left of the galaxy
simultaneously.
A student asked me why it appears in only those four positions and not
at all points around the galaxy.
Can anyone fill in some details on this effect?
Thanks, Dave Abineri
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David Abineri dabineri@choice.net