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Giuseppe Piazzi

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The Reverend
Giuseppe Piazzi
CR
Portrait by Costanzo Angelini, c. 1825
Portrait by Costanzo Angelini, c. 1825
Born Gioacchino Giuseppe Maria Ubaldo Nicolò Piazzi
16 July 1746
Ponte in Valtellina, Duchy of Milan
Died 22 July 1826 (aged 80)
Naples, Kingdom of Naples
Known for Discovery of the first dwarf planet, Ceres
Scientific career
Fields Astronomy
Signature

Giuseppe Piazzi[1] (16 July 1746 – 22 July 1826) was an Italian Catholic priest of the Theatine order, mathematician, and astronomer. He established an observatory at Palermo, now the Osservatorio Astronomico di Palermo – Giuseppe S. Vaiana.[2] He is perhaps most famous for his discovery of the first dwarf planet, Ceres.

Early life

Giuseppe Piazzi was born in Ponte in Valtellina, around 100 km north east of Milan, to a well-to-do family. No documented account of his scientific education exists in any of the astronomer's biographies, even the earliest ones. However, it is certain that Piazzi pursued studies in Turin, likely attending lessons by Giovanni Battista Beccaria. Between 1768 and 1770, he resided at the Theatines' Home in Sant'Andrea della Valle, Rome, where he studied mathematics under François Jacquier.

In July 1770, Piazzi was appointed to the chair of Mathematics at the University of Malta. In December 1773, he moved to Ravenna, where he served as "prefetto degli studenti" and as a lecturer in Philosophy and Mathematics at the Collegio dei Nobili, a position he held until early 1779. After brief periods in Cremona and Rome, Piazzi relocated to Palermo in March 1781, taking up a role as lecturer in mathematics at the University of Palermo (then known as the "Accademia de' Regj Studi")

He kept this position until 19 January 1787, when he became Professor of Astronomy. Almost at the same time, he was granted permission to spend two years in Paris and London, to undergo some practical training in astronomy and also to get some instruments to be specially built for the Palermo Observatory, whose foundation he was in charge of.

In the period spent abroad, from 13 March 1787 until the end of 1789, Piazzi became acquainted with the major French and English astronomers of his time and was able to have the famous altazimuthal circle made by Jesse Ramsden, one of the most skilled instrument-makers of the 18th century. The circle was the most important instrument of the Palermo Observatory, whose official foundation took place on 1 July 1790.

In 1817, King Ferdinand put Piazzi in charge of the completion of the Capodimonte (Naples) Observatory, naming him General Director of the Naples and Sicily Observatories.

Astronomy career

Star cataloguing

He supervised the compilation of the Palermo Catalogue of stars, containing 7,646 star entries with unprecedented precision,[3] including the star names "Garnet Star" from Herschel, and the original Rotanev and Sualocin. The catalogue wasn't finished for first edition publication until 1803, with a second edition in 1814.[4] Piazzi's catalogue was more accurate than any of its predecessors; Franz Xaver von Zach pronounced it epochal, and the Institut de France awarded it the Lalande Prize for the best astronomical work published in 1803.[5]

Spurred by the success discovering Ceres (see below), and in the line of his catalogue program, Piazzi studied the proper motions of stars to find parallax measurement candidates. One of them, 61 Cygni, was specially appointed as a good candidate for measuring a parallax, which was later performed by Friedrich Wilhelm Bessel.[6] The star system 61 Cygni is sometimes still called variously Piazzi's Flying Star and Bessel's Star.

The dwarf planet Ceres

Piazzi discovered Ceres. On 1 January 1801 Piazzi discovered a "stellar object" that moved against the background of stars. At first he thought it was a fixed star, but once he noticed that it moved, he became convinced it was a planet, or as he called it, "a new star".

In his journal, he wrote:

The light was a little faint, and of the colour of Jupiter, but similar to many others which generally are reckoned of the eighth magnitude. Therefore I had no doubt of its being any other than a fixed star. In the evening of the second I repeated my observations, and having found that it did not correspond either in time or in distance from the zenith with the former observation, I began to entertain some doubts of its accuracy. I conceived afterwards a great suspicion that it might be a new star. The evening of the third, my suspicion was converted into certainty, being assured it was not a fixed star. Nevertheless before I made it known, I waited till the evening of the fourth, when I had the satisfaction to see it had moved at the same rate as on the preceding days.

In spite of his assumption that it was a planet, he took the conservative route and announced it as a comet. In a letter to astronomer Barnaba Oriani of Milan he made his suspicions known in writing:

I have announced this star as a comet, but since it is not accompanied by any nebulosity and, further, since its movement is so slow and rather uniform, it has occurred to me several times that it might be something better than a comet. But I have been careful not to advance this supposition to the public.

He was not able to observe it long enough as it was soon lost in the glare of the Sun. Unable to compute its orbit with existing methods, the mathematician Carl Friedrich Gauss developed a new method of orbit calculation that allowed astronomers to locate it again. After its orbit was better determined, it was clear that Piazzi's assumption was correct and this object was not a comet but more like a small planet. Coincidentally, it was also almost exactly where the Titius–Bode law predicted a planet would be.

Piazzi named it "Ceres Ferdinandea," after the Roman and Sicilian goddess of grain and King Ferdinand IV of Naples and Sicily. The Ferdinandea part was later dropped for political reasons. Ceres turned out to be the first, and largest, of the asteroids existing within the asteroid belt. Ceres is today called a dwarf planet.

Posthumous honours

Born in Italy and named in his honour was the astronomer Charles Piazzi Smyth, son of the astronomer William Henry Smyth. In 1871, a memorial statue of Piazzi sculpted by Costantino Corti was dedicated in the main plaza of his birthplace, Ponte. In 1923, the 1000th asteroid to be numbered was named 1000 Piazzia in his honour.[7] The lunar crater Piazzi was named after him in 1935. More recently, a large albedo feature, probably a crater, imaged by the Hubble Space Telescope on Ceres, has been informally named Piazzi.

Works

See also

  • Niccolò Cacciatore, his assistant and successor in the post as director
  • List of Roman Catholic scientist-clerics

From the 1913 Catholic Encyclopedia

Giuseppe Piazzi — Astronomer, b. at Ponte in Valtellina, 16 July, 1746; d. at Naples, 22 July, 1826. He took the habit of the Theatines at Milan and finished his novitiate at the convent of San Antonio. Studying at colleges of the order at Milan, Turin, Rome, and Genoa, under such preceptors as Tiraboschi, Beccaria, Le Seur, and Jacquier, he acquired a taste for mathematics and astronomy. He taught philosophy for a time at Genoa and mathematics at the new University of Malta while it lasted. In 1779, as professor of dogmatic theology in Rome, his colleague was Chiaramonti, later Pius VII. In 1780 he was called to the chair of higher mathematics at the academy of Palermo. There he soon obtained a grant from Prince Caramanico, Viceroy of Sicily, for an observatory. As its director he was charged to get the necessary instruments. He went to Paris in 1787 to study with Lalande, to England in 1788 to work with Maskelyne and the famous instrument-maker Ramsden. A large vertical circle with reading microscopes, a transit, and other apparatus were sent to Palermo in 1789, where they were placed on top of a tower of the royal palace. Observations were started in May, 1791, and the first reports were published as early as 1792. Soon he was able to correct errors in the estimation of the obliquity of the ecliptic, of the aberration of light, of the length of the tropical year, and of the parallax of the fixed stars. He saw the necessity for a revision of the existing catalogues of stars and for the exact determination of their positions. In 1803 he published a list of 6784 stars and in 1814 a second catalogue containing 7646 stars. Both lists were awarded prizes by the Institute of France.

While looking for a small star mentioned in one of the earlier lists he made his great discovery of the first known planetoid, 1 Jan., 1801. Locating a strange heavenly body of the eighth magnitude and repeating the observation several nights in succession, he found that this star had shifted slightly. Believing it to be a comet, he announced its discovery. These few but exact measurements enabled Gauss to calculate the orbit and to find that this was a new planet, between Mars and Jupiter. Kepler and Bode had called attention to the apparent gap between these two, so that the placing of this new body within that space caused great excitement among astronomers. Piazzi proposed the name of Ceres Ferdinandea, in honour of his king. Over 600 of these so-called planetoids have since been located within the same space. The king desired to strike a gold medal with Piazzi's effigy, in commemoration, but the astronomer requested the privilege of using the money for the purpose of a much-needed equatorial telescope. In 1812 he received the commission to reform the weights and measures of Sicily in accordance with the metric system. In 1817 as director-general of the observatories of the Two Sicilies he was charged with the plans of the new observatory which Murat was establishing in Naples. He was a member of the Academies of Naples, Turin, Göttingen, Berlin, and St. Petersburg, foreign associate of the Institute of Milan etc. Besides the numerous memoirs published in the proceedings of the various academies, the following works may be mentioned: "Della specula astronomica di Palermo libri quatro" (Palermo, 1792); "Sull' orologio Italiano e l'Europeo" (Palermo, 1798); "Della scoperta del nuovo planeta Cerere Ferdinandea" (Palermo, 1802); "Præcipuarum stellarum inerrantium positiones mediæ ineunte seculo XIX ex obsrvationibus habitis in specula Panormitana at 1793 ad 1802" (Palermo, 1803, 1814); "Codice metrico siculo" (Catane, 1812); "Lezioni di astronomia" (Palermo, 1817; tr. Westphal, Berlin, 1822); "Raggnaglio dal reale osservatorio d'Napoli" (Naples, 1821).

WOLF, Geschichte der Astronomie (Munich, 1871); MAINERI, L'Astronomo Giovanni Piazzi (Milan, 1871); Cosmos (Paris, 2 March, and 15 June, 1901); KNELLER, Das Christentum (Freiburg, 1904), 75-80.

References

  1. Back to citation US: /ˈpjɑːtsi/ PYAHT-see; "Piazzi". The American Heritage Dictionary of the English Language (5th ed.). HarperCollins. Retrieved 10 August 2019. Italian: [dʒuˈzɛppe ˈpjattsi]
  2. Back to citation Osservatorio astronomico di Palermo – Giuseppe S. Vaiana
  3. Back to citation DavidDarling.com: Piazzi, Giuseppe (1746–1826)
  4. Back to citation Fox 1913.
  5. Back to citation Abetti 1974.
  6. Back to citation On the history of the Palermo Astronomical Observatory by Giorgia Foderà Serio
  7. Back to citation Schmadel, Lutz D. (2003). "(1000) Piazzia". Dictionary of Minor Planet Names – (1000) Piazzia. Springer Berlin Heidelberg. p. 86. doi:10.1007/978-3-540-29925-7_1001. ISBN 978-3-540-29925-7.

Bibliography

Sources

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