What its average distance (semimajor axis) from the sun?

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, P​​​​​​2 =
a​​​​​​3​​​
Where, P is the orbital period in years and a is the semimajor
axis in AU.
or, a​​​​​​3​​​​​ = (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, a​​​​​​Eris​​/a​​​​​aPluto =
67.697/39.482 = 1.714
So, a​​​​​​Eris = 1.714 a​​​​​​Pluto.

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