Apple

A Surface of Revolution defined by Kepler. It consists of more than half of a circular Arc rotated about an axis passing through the endpoints of the Arc. The equations of the upper and lower boundaries in the $x$-$z$ Plane are

$$z_\pm = \pm\sqrt{R^2-(x-r)^2}$$

for $R>r$ and $x\in [-(r+R), r+R]$. It is the outside surface of a Spindle Torus.

See also Bubble, Lemon, Sphere-Sphere Intersection, Spindle Torus