${\displaystyle {\bar {h}}_{ij}(t,r)={\frac {2G}{c^{4}r}}{\ddot {I}}_{ij}(t-r/c),}$
where ${\displaystyle {\bar {h}}_{ij}}$: the spatial part of the trace reversed perturbation of the metric, i.e. the gravitational wave, and ${\displaystyle I_{ij}}$ is the mass quadrupole moment.[1]