Question

In the late nineteenth century, stellar astronomy underwent a fundamental shift as qualitative visual observations yielded to photographic spectroscopy. Edward Charles Pickering’s program at the Harvard College Observatory cataloged thousands of stellar spectra using objective prism photography. To process this unprecedented volume of photographic plates, Pickering employed a team of female calculators, notably Williamina Fleming and Antonia Maury. Fleming established an empirical classification system based primarily on the intensity of hydrogen absorption lines, categorizing stars alphabetically from A to Q. However, Maury subsequently devised a more nuanced scheme that incorporated line sharpness alongside intensity, recognizing subtle spectral distinctions that Fleming’s taxonomy subordinated. While Fleming’s pragmatic approach enabled the rapid processing of over 10,000 stars for the 1890 Henry Draper Catalogue, contemporary astronomers initially dismissed Maury’s structural subdivisions as unnecessarily intricate. It was only decades later, when Annie Jump Cannon synthesized both frameworks into the rearranged O-B-A-F-G-K-M sequence and Meghnad Saha elucidated the thermodynamic mechanisms governing atomic excitation, that Maury’s fine distinctions were recognized to reflect stellar atmospheric pressure and luminosity rather than elemental variance alone. Thus, the initial operational efficacy of Fleming’s taxonomy temporarily obscured the deeper physical insights embedded within Maury’s classification.

Consider each of the choices separately and select all that apply.
Which of the following can be inferred from the passage regarding nineteenth-century stellar spectral classification?