Dust orbit released from a circular parent ring
= Dust orbit released from a circular parent ring
If release imparts no velocity kick, a grain's initial <Kepler orbit> under reduced stellar attraction has $q=r_b$, $Q=r_b/(1-2\beta)$, and $e=\beta/(1-\beta)$ for $0\leq\beta<1/2$. Its <pericentre distance> remains at the <dust birth ring>, while its <apocentre distance> grows with the <radiation-pressure coefficient>.