A Saturn year is 29.5 times the Earth year. How far is the Saturn from the Sun if the Earth is 1.50 \times 10^{8} \mathrm{~km} away from the Sun?
A Saturn year is 29.5 times the Earth year. How far is the Saturn from the Sun if the Earth is 1.50 \times 10^{8} \mathrm{~km} away from the Sun?

According to Kepler’s third law of planetary motion, the following relation can be written,

T=\sqrt{\frac{4 \pi^{2} r^{3}}{G M}}

We get \mathrm{T}^{2} \propto \mathrm{r}^{3} from the above equation.

The orbital period and the mean distance of Saturn from the Sun are \mathrm{T}_{\mathrm{s}} and \mathrm{r}_{\mathrm{s}} respectively.

The orbital period and the mean distance of Earth from the Sun are T_{e} and r_{e} respectively.

Time period of Saturn is T_{s}=29.5 \mathrm{~T}_{\mathrm{e}}

\Rightarrow \mathrm{r}_{\mathrm{s}}^{3} / \mathrm{r}_{\mathrm{e}}{ }^{3}=\mathrm{T}_{\mathrm{s}}^{2} / \mathrm{T}_{\mathrm{e}}^{2}

r_{s}=r_{e}\left(T_{s} / T_{e}\right)^{2 / 3}

=1.5 \times 10^{8} \times 29.5^{2 / 3}

=14.3 \times 10^{8} \mathrm{~km}