Photogravitational force might be deduced as follows.

where phi is photogravitaional constant and Ts is surface temperature of astronomic object.

The difference between surface temperature and core temperature is also important for near field gravity. with lattitude, it increases resulting in value between 9.78 and 9.82 m/s^2
To take care of differntial effect, It can be modified as follows.

where and

We want to match centrifugal and centripetal force,

We have derived the inverse biquadrate counterpart of Kepler 3rd law,