A Gallery of Lenses (3) ...

The adjacent right animation illustrates some calculations for a mathematical model of a gravitational lens. The elliptical lensing mass is fixed and in successive frames the position of the more distant point source is moved relative to the center of the lensing mass (we draw the source as somewhat extended to make it easier to follow in the animation).

In this example the lensing mass is assumed to lie at a redshift of 0.313, while the source lies at a redshift of 0.626. The lensing mass is assumed to be elliptical, and is several arc seconds in extent. The images produced by the lens are seen to cover a region of the sky approximately 20 arc seconds around the position of the lensing mass. A large variety of lensing effects is observed, including an Einstein cross when the lens and source are almost exactly aligned.