astronomy questions

Question

the eccentricity of an ellipse is always a fraction, btw 1 and 0, and it has no units.

true/false?

Answer 1

True, for an ellipse the eccentricity is the ratio of two lengths, distance from center to focus c divided by semi-major axis a. Because the focus is inside the ellipse, c < a, therefore the ratio is between 1 and 0 with no units.