Comet Halley returns to the Sun's vicinity approximately every 76 years in an elliptical orbit. According to Kepler's third law, what is the semimajor axis of this orbit?
A) 0.59 au
B) 17.9 au
C) 50.000 au
D) 1 au

Question

Quizplus · Accepted Answer

Kepler's third law states that the square of the orbital period (in years) of a planet is directly proportional to the cube of the semi-major axis of its orbit (in astronomical units, au). For Comet Halley, with an orbital period of approximately 76 years, the semi-major axis can be calculated using the formula $P^2 = a^3$, where $P$ is the period in years and $a$ is the semi-major axis in astronomical units. Solving for $a$ gives a semi-major axis of approximately 17.9 au.

Comet Halley Returns to the Sun's Vicinity Approximately Every 76