Italian astronomer and astrophysicist who classified stellar
spectra into four classes based on their colour and spectral characteristics.
He was the first to classify solar prominences, huge jets of gas projecting
from the Sun's surface.
Secchi was born in Reggio nell'Emilia and became a Jesuit priest, lecturing
in physics and mathematics at the Collegio Romano from 1839. In 1848
he was driven into exile for being a Jesuit and went first to Stonyhurst
College, England, then to Georgetown University in Washington DC. He
returned to Italy 1849 as director of the observatory at the Collegio
Romano and professor of astronomy.
With English astronomer William Huggins, Secchi was the first person
to adapt spectroscopy to astronomy in a systematic manner and he made
the first spectroscopic survey of the heavens. He proposed that the
differences in stellar spectra reflected differences in chemical composition.
His classification system of 1867 is the basis of the modern system.
Secchi was among the first to use the new technique of photography for
astronomical purposes. By 1859 he had a complete set of photographs
of the Moon.