Giovanni Battista Hodierna was born on April 13, 1597 in Ragusa, Sicily. In his teenage years he observed three kites between 1618 and 1619, with a Galilean-type telescope. He was ordained as a Catholic cleric in Syracuse, where he taught mathematics and astronomy. He was an enthusiastic follower of Galileo.
In 1628 Hodierna wrote the "Nunzio del cristalolo secolo", an evaluation of the "Siderius Nuntius". He was particularly impressed with the resolution of stars in the Milky Way and in clusters such as the manger. His works focused especially on the study of the Solar System.
In 1637 he moved to the newly founded Palma di Montechiaro. He lived and began to make his publications and served as a clergyman for the community. In 1644 he received a doctorate in theology. In 1645 he was appointed archbishop and in 1655 mathematician of the court.
Hodierna practiced other sciences such as natural philosophy, physics and botany. He studied the fragmentation of light as he passed through a prism and approached the explanation of the Rainbow. He developed a microscope with which he studied the eyes of a wide variety of insects. He was also a student of meteorological phenomena.
His studies in astronomy had little impact because his publications were local and also because he mixed astronomy with astrology. That is why its place in history is not in the place it deserves.
In 1646 and 1653 Hodierna observed and drew Saturn showing his ring correctly and published "Protei caelestis vertigines sev. Saturni systema", in 1657 which is, perhaps, one of his best known works.
In 1652 he observed the movements of the moons of Jupiter giving rise to his work "Medicaeorum Ephemerides", probably the best produced by him, improving the theory of the movements of these satellites.
In 1656 he published "De Admirandis Phasibus in Sole et Luna visis", studies of the Moon and the Sun including sunspots and eclipses. One of his most interesting works was entitled "De systemate orbis cometici; deque admirandis coeli characteribus", published in 1654.
Hodierna thought that there were great differences between comets and nebulas mainly because, over time, comets changed their shape. That is why he believed that comets were made of terrestrial material and nebulas of star material.
He described a list of 40 nebulas which he classifies according to the ability to solve them in stars in: Luminous (views of the naked eye), Nebulas (Solved with telescopes) and Hidden (not resolved even with telescope).
His discoveries of deep space were compiled in the atlas, "Il Cielo Stellato Diviso in 100 Mappe", a work that remained unfinished. Hodierna's catalog of nebulous objects includes rediscoveries independent of the Andromeda galaxy, the Orion nebula, and probably independent discoveries of many other astronomical objects.
Hodierna died on April 6, 1660 in Palma di Montechiaro, Sicily.
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