Question

Why does Neptune take 165 Earth years to revolve around the Sun, while Jupiter only needs 11.9 Earth years to do so?
A Neptune is lighter than Jupiter.
B Neptune spins slower than Jupiter.
C The Sun is closer to Jupiter than to Neptune.
D The density of Neptune is higher than that of Jupiter.

Answer 1

C

Neptune takes much longer because it orbits much farther from the Sun. By Kepler’s third law the orbital period increases with the size of the orbit (P^2 ∝ a^3), so the more distant Neptune (≈30 AU) has a much longer period than Jupiter (≈5.2 AU). The other options (mass, spin, density) do not determine orbital period around the Sun.