Question

figure 4: the focal length in astronomical units (au) and major axis length (au) of two planets

planet	focal length in au (f)	major axis length in au (d)
b	5	9

calculate the eccentricity for planet a. use information in figure 4 and the formula: $e = f/d$
options: 0.4, 0.555, 0.667, 2.5

Explanation:

Step1: Identify values for Planet A

For Planet A: focal length $f=2$ AU, major axis length $d=5$ AU

Step2: Apply eccentricity formula

Use $e=\frac{f}{d}$, substitute values.
$\displaystyle e=\frac{2}{5}$

Step3: Compute the result

Calculate the fraction to decimal form.
$\displaystyle e=0.4$

Answer:

0.4