# How do you calculate a planet's perihelion distance? For example, a planet has a perihelion distance of 1 A.U. and a semi major axis of 234.89 A.U. What is its aphelion distance?

Nov 22, 2015

Aphelion = 468.79 AU

#### Explanation:

The Semi Major axis of an ellipse is given by a. So, a = 234.89 AU

The formula for Perihelion period is given by,

Perihelion = a(1 - e)

and for Aphelion, it is given by,

Aphelion = a(1 + e)

Where, is the eccentricity of the object's orbit.

Given,

Perihelion = 1 A.U

1 = 234.89(1 - e)
$\frac{1}{234.89}$ = 1 - e

$0.0042 = 1 - e$

$e = 1 - 0.0042$

$e = 0.9958$

Aphelion = a(1 + e)

Aphelion = 234.89(1 + 0.9958)

Aphelion = 468.79 AU