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=?

## Answer

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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