Figure 23-32:
Gravitational Lensing (a) A massive object such as a galaxy can deflect light rays like a lens so that an observer sees more than one image of a more distant galaxy. (b) An Einstein Ring is produced when a distant object is lined up almost exactly behind the lens.
Gravitational Lensing (a) A massive object such as a galaxy can deflect light rays like a lens so that an observer sees more than one image of a more distant galaxy. (b) An Einstein Ring is produced when a distant object is lined up almost exactly behind the lens.
(b: ESA/Hubble & NASA)