Fr. Angelo Secchi, S.J.
Fr. Angelo Secchi SJ, director of the Roman College Observatory from 1850 until his death in 1879, produced profound advances in science in half a dozen widely divergent fields: meteorology, time keeping, surveying and geodesy, planetary geology, spectroscopy of the stars and the planets, stellar classification, solar physics, and the “sun-Earth connection” between solar activity and the Earth’s magnetosphere. He was also well published in popularization and philosophy.
Secchi was born in Reggio Emilia on June 28th, 1818. He studied at the local Jesuit college and, at the age of fifteen entered the Society of Jesus. In 1837 his physics professor, Giovanni Battista Pianciani SJ, remarked that the young Jesuit was gifted in scientific studies. From 1841 to 1844 Secchi taught physics at the Jesuit school in Loreto. Upon his return to the Collegio Romano, he became Pianciani’s assistant.
In 1847 Secchi was ordained a priest. But the following year, the political situation became unstable in Italy and, Secchi, with the other Jesuits, was forced to leave Italy. He spent some months in England at Stonyhurst College and then, at the end of 1848, he moved to Georgetown College, in the United States, to teach physics. There Secchi began to be incorporated into the local scientific milieu, especially Commodore Matthew F. Maury, from whom Secchi learnt much about new theories of dynamic meteorology, and the physicist Joseph Henry, Secretary of the Smithsonian Institution.
In 1849 the Papal Government was re-established and the Jesuits could return to Rome. The death of Fr. Francesco De Vico had left the directorship of the Roman College Observatory vacant, and Secchi, only 30 years old, was appointed Director.
Assigning a physicist the job of an astronomer turned out to be crucial for the future scientific program of the observatory. Before Secchi, astronomy was only the study of the positions of the stars and planets and the calculation of their orbits. But Secchi was the first person to think about the lights in the sky as places with their own compositions and histories. He, and those he encouraged, invented modern astrophysics and planetary sciences.
Others had noted that the Sun had a unique spectrum; Secchi used spectroscopy to answer specific questions about the solar constitution. Others had noted that one could even see spectra in bright stars; Secchi measured the spectra of thousands of stars, looking for patterns and ways to classify them. Furthermore, he also took the spectra of planets, identifying their atmospheres.
No one before Secchi had bothered to actually try to inspect the surface of Mars and make sense of its surface markings in terms of geological processes. Secchi’s work inspired the pioneer maps of Schiaparelli and Lowell, who infamously borrowed Secchi’s term canale (channels) to describe features that turned out to be optical illusions. By contrast, the much wider features that Secchi described as canale are real.
Secchi is also remembered today for two instruments that bear his name. The Secchi Disk he apparently made one afternoon, as a favor for a friend looking for a repeatable way to measure the clarity of water. The other is an instrument on the NASA STEREO spacecraft monitoring solar activity, the Sun-Earth Connection Coronal and Heliosphere Investigation (SECCHI) package, in honor of his pioneering work correlating terrestrial magnetism with solar activity.