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Jul2-11, 07:17 AM
P: 2,195
Abundance of hydrogen in Sun

The 26% He by weight is more representative of the composition of the sun at the time of formation. The sun has been burning H to He for 4.5 billion years, so according to the standard solar model, the interior of the sun is now over 60% He. To calculate the atomic ratio, you would need to integrate over the whole volume - I don't know the answer, but I'm sure it is more than 26% He by weight when averaged over the whole sun. Here are a couple of references with Figure 2 in the first reference showing the mass fraction as a function of radius, and Table 1 in the second reference giving the He mass fraction in the core at >60%.