Secchi, Pietro Angelo (pyĕˈtrō änˈjālō sĕkˈkē) [key], 1818–78, Italian astronomer, a Jesuit priest. He was director of the observatory of the Gregorian Univ., Rome, from 1849. He is known especially for his work in spectroscopy and was a pioneer in classifying stars by their spectra. In 1860 he made some notable solar-eclipse photographs. His works include a star catalog (1867).