3. Cecelia Payne-Gaposchkin was the physicist who was able to put everything together, showing that the spectra of stars depended on the and the in their atmospheres. She showed that stars were mainly with the next most abundant element being .

Showing that the spectra of stars depended on the ___temperature and the degree of ionization of elements in their atmospheres.

She showed that stars were mainly   hydrogen with the next most abundant element being  helium .

Explanation:

Cecilia Payne worked at the Harvard College Observatory (HCO) where she analyzed for months the spectra of hundreds of stars; she aimed to calculate the elements present in them; and from her observations and studies over the years she discovered the information quoted above.