Q:  What is the value of R_min in meters?  In AU?

                      G * (1.99 x 10^(30) kg)^2
           R_min  =  ---------------------------
                           ( 25 x 10^(3) m/s )^2
 


                  =   4.2 x 10^(11) m

 
                  =   approx 3 AU


   Q:  How does it compare to the physical size of the Sun?


            This is about 600 solar radii -- so considerably
            larger than the radius we used for a physical collision.