to the right is a simulation depicting a zoom on a schwarzschild black hole in the plane of the milky way between us and the centre of the galaxy. the first einstein ring is to the most distorted region of the picture and shows the galactic disc. the zoom then reveals a series of 4 extra rings, increasingly thinner and closer to the black hole shadow. they are multiple images of the galactic disk. the first and third correspond to points which are behind the black hole (from the observer's position) and correspond here to the bright yellow region of the galactic disc (close to the galactic center), whereas the second and fourth correspond to images of objects which are behind the observer, which appear bluer since the corresponding part of the galactic disc is thinner and hence dimmer here.