Here we see a collection of lines that are normal to an ellipse. The
points were nearby normals intersect are the centers of the circles of
curvature for the ellipse. These centers lie along the focal curve, or
evolute for the curve. In the case of an ellipse, the evolute is an
astroid, which we can see in the image as a light caustic in the form of a
glowing, four-pointed "star".
This image is from Beyond the Third Dimension, and is closely
related to Ellipse Spotlights and
Sandpile Chalice. The normals to
an ellipse were a central theme within the video Fronts and Centers.