Final answer:
Edward C. Pickering, the director of the Harvard Observatory, gathered data on stars for many years but died before he could publish it, leaving a legacy that contributed significantly to stellar classification.
Step-by-step explanation:
The individual in question who gathered data on the stars for over five years but unfortunately died before he could publish his data was Edward C. Pickering, the director of the Harvard Observatory.
His efforts in the late 1800s were part of a large-scale project that included the classification of stellar spectra based on a collection of nearly a million photographic spectra of stars.
These spectra were the result of many years of observations, and they provided a foundation for further astronomical research and understanding of stellar properties.