Father Angelo Secchi (June 29, 1818 – February 26, 1878)
When discussing the relationship between astronomy and religion one often recounts the tension between Galileo and the Catholic Church in the 17th century. But the Vatican has hosted its own astronomical observatories for many years, and some of the discoveries made in these facilities have changed astronomy forever. A case in point is the work of Father Angelo Secchi, who died on this day in 1878. Father Secchi was a pioneer in the study of the spectra of stars. By passing starlight through a prism, astronomers can divide the white light into its constituent colors, allowing us to determine what stars are made of. Father Secchi did his work before spectra could be photographed. Hence his spectra were captured by the eye and hand, put onto paper through watercolors or colored pencils. His scientific papers were not only brilliant, but beautiful to look at.
Father Secchi developed one of the very first spectral classification systems, as illustrated above. While large photographic surveys led to new classification systems, his work was an important first step in our understanding of stars, and for this reason we remember and honor Father Secchi on the anniversary of his death.