- #1

jaumzaum

- 434

- 33

Another doubt, in Third Kepler law seen below:

##\frac{T^2}{a^3}=\frac{4\pi^2}{G(M+m)}##

The "a" is calculated in relation to the other planet (the referential is the second planet) or in relation to an inertial frame?

To illustrate what I mean above, If we consider two bodies, of masses M and 3M, the maximal distance between them is x and the minimum is y. Haw can we calculate the period and the semi-major axes and eccentricities of both ellipses?

Thank you very much