| Angelo Secchi was born on the 18th of June, 1818 in Reggio, Italy. At the age of 15, be joined the Jesuit order. In 1844, Angelo began his theological studies and was ordained a priest three years later. His primary interest was the natural sciences - especially physics and mathematics. He lectured at the Collegio Romano in 1839 until 1848 when he left due to political unrest in Italy that eventually led to the expulsion of the Jesuits. At this point, he traveled to England, and later to Georgetown University, and then returning to Europe. In 1852, he returned to Rome, and founded a new observatory at the Collegio Romano where he remained until his death on 26 February 1878.
Of his contributions to astronomy, he is most well known for his work on stellar spectral classification based upon the strength of the hydrogen absorption line in the spectra. This was the first use of spectroscopy systematically used for classifying the types of stars. His classifications were the foundations upon which the modern system is based.
Angelo Secchi was also very interested in solar physics. His
studies included solar prominences which were visible during eclipses.
These studies provided the first demonstrations that prominences
are features of the sun. He also wrote a number of books on astronomy
ranging from technical treaties to astronomy for the general public to
astronomy for children.
As the father of modern astrophysics, he was the first to suggest
that the core of the sun was a gas with the temperature of the gas
decreasing steadily from the center to the surface. While his
theories on sunspots and prominences have been obsoleted, his
impact on science at the time was considerable.
He is also very well known for the Secchi disk which is used to
measure the clarity of water.
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