What is the common radius of gyration Between the Sun & all the planets?

Answer 1

The best model to use is that of a particle disrtibution. Note that this is a summation.
R^2=(Summation from 1 to N (r(step) - r(mean)^2))/N also be aware that r(mean) is the mean position of the particles.

Obviously, you become more accurate the more planets and asteroids you include in this, but to be honest, you would most likley would exceed your significant figures after performing calculations for just the sun and Jupiter and perhaps Saturn. After that, any variation in your calculations would probably fall within the margin of error.

So is this a Celestial Mechanics class?