Finding the eccentricity of Earth's orbit

[dimensionless]

Given the mass of the sun, the gravitational constant, the period of Earth's orbit, and the semi-major axis of Earth's orbit, is it possible to find the eccentricity of the orbit? If yes, how?

 

[quantumdude]

Kindly post your own thoughts on the matter, as per the Physics Forums Guidelines, which you agreed to.

 

[dimensionless]

I'm really not sure if it can be done. If it can I don't know how. I guess that maybe it can't be done, since there appears to be no way to find to foci.

This is not actually a homework question by the way.