| Name | Formula | where |
| Keplers 3rd Law | \begin{align*}a^3 = \frac{GMP^2}{4\pi^2} \end{align*} | \begin{align*}
a &= \text{Semi-major axis of elliptical orbit}\\
G &=\text{constant}\\
M &=\text{total mass of orbiting bodies}\\
P &=\text{orbital periode}\\
\end{align*} |
| Keplers 3rd law in simplified units | \begin{equation}
a^3 = P^2M
\end{equation} | \begin{align*}
a &= \text{Semi-major axis of elliptical orbit in Units of AU}\\
M &=\text{total mass of bodies in masses of sun}\\
P &=\text{orbital period in years}\\
\end{align*} |
| Keplers 3rd law when mass of planet is much smaller than the star $\frac{M}{M_\odot} \approx 1$ | \begin{equation}
a^3 = P^2
\end{equation} | \begin{align*}
a &= \text{Semi-major axis of elliptical orbit in Units of AU}\\
P &=\text{orbital period in years}\\
\end{align*} |