A distant star has a single plante orbiting at a radius of 3.51X10^11m. The period of the planet's motion around the star is 853 days. What is the mass of the star? The universal gravitational constant is 6.67259X10^-11N m^2/kg^2. Answer in kg. Alrighty. So I tried to find the mass by using the equation: T^2=(4pi)^2 X R^2/Gm so that became: (73699200sec)^2=(4pi)^2 X (3.51X10^11)/(6.67259X10^-11)X(mass star) (5.43157X10^15)=(5.5427X10^13)/(6.67253X10^-11)X(m) thus m=6.5388X10^-9 Even I noticed that the answer shouldn't work and doesn't make sense. Can anyone see where I went wrong, or have a better approach?