Phase-mixed radial probability of a Kepler orbit
= Phase-mixed radial probability of a Kepler orbit
{title2=$p_r(r)$}
For a <Kepler orbit> with <pericentre distance> $q$, <apocentre distance> $Q$, and <semi-major axis> $a=(q+Q)/2$, a uniform <mean anomaly> gives
$$
p_r(r)=\frac{r}{\pi a\sqrt{(r-q)(Q-r)}},\qquad q<r<Q.
$$
The two radial passages per <orbital period> are included, and $\int_q^Qp_r(r)\,dr=1$.