Our present theory of the Sun's internal structure is in some significant way based on our knowledge of:

a. the oldest biological growth records on earth being used to determine the constancy of the Sun’s luminosity over the largest part of its’ prior main sequence lifetime.
b. the fact that Jupiter has a composition thought to be identical to the Sun's.
c. the length of time it takes the Jupiter to orbit once around the sun to determine the Sun’s angular momentum.
d. the spectrum of the light coming from the Sun to determine the details of the Sun’s composition at its outer surface.
e. the period and semi-major axis of the earth's orbit to determine the Sun’s mass.