Helioseismology is the study of rhythmic oscillations observed on the 'surface' of the Sun.
Imagine a scientist listening to a live symphony in an orchestral hall. The scientist is now blindfolded and we switch out the orchestra and replace it with a high quality reproduction. The scientist cannot tell the difference. In the same manner, how does a scientist know if the object is a Sun with a dense interior or a empty shell? All the scientist has to go on is past experience, and I suggest that in this case the experience is faulty.