Kepler's Third Law: Mass of Sun and Newton's Law

[The legend]

I read somewhere that the mass of the sun can be determined using Keplers third law. How is this possible without indulging Newton's law(gravitation) in ?

 

[zhermes]

It can be determined using kepler's third law, but not with kepler's third law alone. Only the ratios of different periods and semi-major axes can be compared with kepler's third law.

 

[The legend]

That's what i felt.. thanks for the reply