A planet is in circular orbit around the Sun. Its distance from the Sun is four times the average distance of Earth from the Sun. The period of this planet, in Earth years, is:

Question

Quizplus · Accepted Answer

According to Kepler's third law, the square of the period of a planet is proportional to the cube of its average distance from the Sun. Let's use Earth's average distance from the Sun as 1 astronomical unit (AU). Therefore, the distance of the planet from the Sun is 4 AU.

Using Kepler's third law:

(T planet)^2 / (a planet)^3 = (T earth)^2 / (a earth)^3

(T planet)^2 / (4)^3 = (1)^2 / (1)^3

(T planet)^2 / 64 = 1

(T planet)^2 = 64

T planet = 8 Earth years.

Therefore, the answer is B) 8.

A Planet Is in Circular Orbit Around the Sun