Proper-eccentricity annulus
= Proper-eccentricity annulus
For a common <semi-major axis> $a$ and <proper eccentricity> $e_p$, randomly distributed <proper longitudes of periapsis> give an <annulus> of radii $a(1-e_p)$ and $a(1+e_p)$ about the point displaced from the <star> by minus $a$ times the <forced eccentricity> vector, to first order in <orbital eccentricity>.