Short precession periods like 164d of SS433 can be well determined by observations of time scales longer or much longer than the precession period .
However , it doesn ’ t work for sources with precession periods of millions of years .
This paper utilizes the particular morphologies of X-shaped sources , so that the 3 dimension kinematics of lobes can be obtained .
Thus , for the first time , the million-year precession period of X-shaped sources by observer on the Earth can be determined elegantly : ( 6.1 \pm 1.5 ) Myr , ( 1.8 \pm 0.5 ) Myr , and ( 3.2 \pm 1.2 ) Myr for 3C52 , 3C223.1 and 4C12.03 respectively .
The result naturally explains the asymmetry displayed in the morphology of these sources , and the effect of propagation time on the diversity of morphologies is well demonstrated .
The precession period may originate from long-term effects of a binary super-massive black hole system , which is a potential source of gravitational wave radiation .