The dwarf planet Eris orbits the Sun every 557 years.
1. What its average distance (semimajor axis) from the Sun?
Answer in -----Eris's semimajor axis= ? A.U
2. How does its average distance compare to that of Pluto?
Answer in -----aEris/aPluto=?
1) Given : Orbital period of Eris (P) = 557 years.
Semimajor axis (a) = ?
From Kepler's third law, P2 = a3
Where, P is the orbital period in years and a is the semimajor axis in AU.
or, a3 = (557)2 = 310249 AU
or, a = 67.697 AU
2) Semi major axis of Pluto = 39.482 AU.
Semi major axis of Eris = 67.697 AU
Therefore, aEris/aaPluto = 67.697/39.482 = 1.714
So, aEris = 1.714 aPluto.