Suppose we wanted to represent all of these objects on the 1-to-10-billion scale from chapter 1, on which the sun is about the size of a grapefruit. approximately how large in diameter would the star aldebaran be on this scale?

6.62 m

About 44.14 grapefruits lined in a single line would be the length of the diameter of star Aldebaran

Explanation:

First we know,

Diameter of the Sun - 1.39 million km (Ds)

Diameter of Aldbaran - 61.40 million km (Da)

Thus,

=   ≈ 44.14

We know that in this scale the size of the sun is that of a grapefruit.

The average diameter of a grapefruit is about 15cm

Thus  Ds in this scale is 15cm

Thus Da in this scale,

Da = Ds *44.14

Da = 0.15 * 44.14 ≈ 6.62 m

Thus the diameter of Aldebaran in this scale is 6.62 m