# . If a planet’s closest distance to the Sun is 1.00 AU, and its furthest distance from the sun is 9.00 AU, what would its orbital period be?

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How do I solve this?

How do I solve this?

##### 1 Answer

#### Answer:

The planet takes 11.2 earth years to complete one orbit.

#### Explanation:

The orbit described here is highly elliptical as opposed to being nearly circular. If we add the distance of nearest approach to the sun and the greatest of greatest separation, we get what is called the major axis of the ellipse that describes the orbit.

To solve this problem, we will use Kepler's third law:

but it is convenient to know that

In this case, the semi-major axis is 5 AU.

Because the distances are in AU, we can set the constant

Here goes: