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GIUSEPPE PIAZZI (1746 - 1826)

Giuseppe Piazzi was born in Ponte di Valtellina, Italy (now in Switzerland) in 1746. Little is known about his life until he joined the Theatine order in 1764, entering the convent of San Antonio. After completing his training to become a monk he continued his studies in Theatine colleges in a variety of Italian cities. Piazzi was particularly gifted at mathematics and astronomy and, in 1779, he was appointed as Professor of Mathematics at the Palermo Academy in Sicily.

Not long after he took up his post he was given a grant by the Viceroy of Sicily, Prince Caramanico, to build an observatory on the island. Piazzi travelled to Paris (1787) and London (1788) to search out the equipment he would need. This equipment arrived in Sicily in 1789 and the observatory was set up on a tower of the Prince’s palace. It was ready for use in 1791 and Piazzi began his observations. By 1803 he had catalogued 6784 stars with great accuracy and he had increased this list to 7646 stars by 1814. Piazzi won prizes from the Institute of France for the accuracy of his star catalogues.

Giuseppe Piazzi

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In 1801 Piazzi discovered what he thought to be a new star. However, further observations showed this object to be moving and so he concluded it was a comet. Piazzi observed his “comet” over the next five days and was surprised by its movement, which seemed too slow and straight to be a comet. He started to think that it might be a new planet but he did not admit to this in his report on the object, calling it a comet. A mathematician, called Carl Friedrich Guass, was able to use Piazzi’s recorded observations to calculate the orbit of the object. This allowed astronomers to find it again. It soon became clear that it was not a comet at all but what appeared to be a small planet.

We now know that Piazzi had discovered the largest asteroid in the asteroid belt that he named Ceres. Since his discovery more than 1000 asteroids have been identified and the 1000th was named Piazzi in tribute to the Italian monk. Piazzi himself went on to introduce the metric system in Sicily in 1812 which involved reforming the weights and measures. He also planned and supervised the building of an observatory at Naples in 1817.

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