Quadrupole approximation
= Quadrupole approximation
In a hierarchical orbital system, the quadrupole approximation keeps the first nontrivial term beyond the monopole in the orbit-averaged expansion in the ratio of inner to outer separation.
= Quadrupole approximation
In a hierarchical orbital system, the quadrupole approximation keeps the first nontrivial term beyond the monopole in the orbit-averaged expansion in the ratio of inner to outer separation.