The dwarf planet Eris has an orbital period about the Sun, P of 557 years. Given this, what is the semimajor axis, a of its orbit?
A) 67.7 AU
B) 55.7 AU
C) 38.4 AU
D) 72.1 AU

Question

Quizplus · Accepted Answer

Using Kepler's Third Law, P^2 = a^3, where P is in years and a is in astronomical units (AU). Solving for a, we get a = (P^2)^(1/3). Substituting P = 557 years, we find a ≈ 67.7 AU.

The Dwarf Planet Eris Has an Orbital Period About the Sun