Question

Jupiter’s moon, Ganymede takes 7.15 Earth days to orbit Jupiter. Ganymede is measured to be 7.1 X 10-3 AU from Jupiter’s center. A second moon of Jupiter, Callisto, takes 16.69 Earth days to orbit Jupiter. How far away is Callisto from the center of Jupiter?

Answer 1

Answer:

0.0124 AU

Explanation:

Ganymede takes 7.15 Earth days to orbit Jupiter. Ganymede is measured to be 7.1 X 10⁻³ AU from Jupiter’s center.

We need to find how far away is Callisto from the center of Jupiter if a second moon of Jupiter, Callisto, takes 16.69 Earth days to orbit Jupiter. Let it is r₂. Using third law of Kepler.

$T^2\propto r^3$

i.e.

$(\dfrac{T_1}{T_2})^2=(\dfrac{r_1}{r_2})^3\\\\\dfrac{r_1}{r_2}=(\dfrac{T_1}{T_2})^{2/3}\\\\r_2=\dfrac{r_1}{(\dfrac{T_1}{T_2})^{2/3}}\\\\r_2=\dfrac{7.1\times 10^{-3}}{(\dfrac{7.15}{16.69})^{2/3}}\\\\r_2=0.0124\ \text{AU}$

So, Callisto is 0.0124 AU from the center of the Jupiter.