Cecilia Payne-Gaposchkin was a British mathematician and astronomer who did important work for her Ph.D. at Radcliffe College of Harvard University. She showed that stars were composed almost entirely of hydrogen and helium but, although completely correct, it was rejected by astronomers at the time.
Find out more at: https://mathshistory.st-andrews.ac.uk/Biographies/Payne-Gaposchkin/