Editing Giuseppe Piazzi

{{Short description|Italian Catholic priest, mathematician and astronomer (1746–1826)}}
{{for|the Italian bishop|Giuseppe Piazzi (bishop)}}
{{refimprove|date=February 2010}}
{{EngvarB|date=July 2017}}
{{Use dmy dates|date=January 2025}}
{{Infobox scientist
|honorific_prefix  = [[The Reverend]]
|name              = Giuseppe Piazzi
|honorific_suffix  = [[Theatines|CR]]
|image             = Costanzo Angelini, L'astronomo Piazzi 1825 ca.jpg
|image_size        = 
|caption           = Portrait by [[Costanzo Angelini]], {{circa|1825}}
|birth_date        = {{Birth date|df=yes|1746|7|16}}
|birth_place       = [[Ponte in Valtellina]], [[Duchy of Milan]]
|death_date        = {{death date and age|df=yes|1826|7|22|1746|7|16}}
|death_place       = [[Naples]], [[Kingdom of Naples]]
|residence         =
|citizenship       =
|nationality       = [[Italians|Italian]]
|ethnicity         =
|field             = [[Astronomy]]
|work_institutions ={{hlist|[[University of Malta]]|[[University of Palermo]]|[[Palermo Astronomical Observatory]]}}
|alma_mater        =
|doctoral_advisor  =
|doctoral_students =
|known_for         = Discovery of the first dwarf planet, [[Ceres (dwarf planet)|Ceres]]
|author_abbrev_bot =
|author_abbrev_zoo =
|influences        =
|influenced        =
|prizes            = [[Lalande Prize]] (1803)
|footnotes         =
|signature         =
}}

'''Giuseppe Piazzi''' {{post-nominals|post-noms=[[Theatines|CR]]}} ({{IPAc-en|US|ˈ|p|j|ɑː|t|s|i}} {{respell|PYAHT|see}},<ref>{{Cite American Heritage Dictionary|Piazzi|access-date=10 August 2019}}</ref> {{IPA|it|dʒuˈzɛppe ˈpjattsi|lang}}; 16 July 1746 – 22 July 1826) was an Italian [[Catholic Church|Catholic]] priest of the [[Theatines|Theatine order]], mathematician, and [[astronomer]]. He established an observatory at [[Palermo]], now the ''[[Palermo Astronomical Observatory|Osservatorio Astronomico di Palermo]] – Giuseppe S. Vaiana''.<ref>[http://www.astropa.unipa.it/ Osservatorio astronomico di Palermo – Giuseppe S. Vaiana]</ref> He is perhaps most famous for his discovery of the first dwarf planet, [[Ceres (dwarf planet)|Ceres]].

== Early life ==

No documented account of Piazzi's 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 Giovan 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, [[Ferdinand I of the Two Sicilies|King Ferdinand]] put Piazzi in charge of the completion of the [[Capodimonte Observatory|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,<ref>[http://www.daviddarling.info/encyclopedia/P/Piazzi.html DavidDarling.com: Piazzi, Giuseppe (1746–1826)]</ref> including the star names "[[Mu Cephei|Garnet Star]]" from [[William Herschel|Herschel]], and the [[Sualocin and Rotanev|original]] [[Rotanev]] and [[Sualocin]]. The work to observe the sky methodically. The catalogue wasn't finished for first edition publication until 1803, with a second edition in 1814.{{sfn|Fox|1913}}

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]].<ref>[http://www.astropa.unipa.it/HISTORY/history.htm On the history of the Palermo Astronomical Observatory] by Giorgia Foderà Serio</ref> The star system [[61 Cygni]] is sometimes still called variously ''Piazzi's Flying Star'' and ''Bessel's Star''.

===The dwarf planet Ceres===
{{unref-section|date=February 2021}}
[[File:Ceres-Beobachtung von Piazzi.png|thumb|Piazzi's observations published in the [[:de:Monatliche Correspondenz|Monatliche Correspondenz]], September 1801]]

Piazzi discovered [[1 Ceres|Ceres]]. On 1 January 1801 Piazzi discovered a "stellar object" that moved against the background of [[star]]s. 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: {{quote|The light was a little faint, and of the colour of [[Jupiter]], but similar to many others which generally are reckoned of the eighth [[Apparent magnitude|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:

{{quote|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 mythology|Roman]] and Sicilian [[Ceres (Roman mythology)|goddess of grain]] and [[Ferdinand I of the Two Sicilies|King Ferdinand IV]] of [[Naples]] and [[Sicily]]. The Ferdinandea part was later dropped for political reasons. [[Ceres (dwarf planet)|Ceres]] turned out to be the first, and largest, of the [[asteroid]]s 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.<ref name="1000-Piazzia" /> The lunar crater ''[[Piazzi (crater)|Piazzi]]'' was named after him in 1935. More recently, a large [[albedo]] feature, probably a [[Impact crater|crater]], imaged by the [[Hubble Space Telescope]] on Ceres, has been informally named ''Piazzi''.

==Works==
[[File:Piazzi, Giuseppe – Discorso recitato nell'aprirsi la prima volta la Cattedra di astronomia nell'Accademia de' r. Studj di Palermo, 1790 – BEIC 4642534.jpg|thumb|''Discorso recitato nell'aprirsi la prima volta la Cattedra di astronomia nell'Accademia de' r. Studj di Palermo'', 1790]]
* {{Cite book|title=Discorso recitato nell'aprirsi la prima volta la Cattedra di astronomia nell'Accademia de' r. Studj di Palermo|volume=|publisher=Stamperia reale|location=Palermo|year=1790|language=it|url=https://gutenberg.beic.it/webclient/DeliveryManager?pid=4642534}}

==See also==
* [[Niccolò Cacciatore]], his assistant and successor in the post as director
* [[List of Roman Catholic scientist-clerics]]

==References ==
{{reflist|refs=

<ref name="1000-Piazzia">{{cite book
  |title=Dictionary of Minor Planet Names – (1000) Piazzia
  |last=Schmadel |first=Lutz D.
  |publisher=[[Springer Berlin Heidelberg]]
  |page=86
  |date=2003
  |isbn=978-3-540-29925-7
  |doi=10.1007/978-3-540-29925-7_1001
  |chapter = (1000) Piazzia}}</ref>

}}

==Sources==
* Clifford Cunningham, Brian Marsden, Wayne Orchiston. (2011) "Giuseppe Piazzi: the controversial discovery and loss of Ceres in 1801." ''Journal for the History of Astronomy'', Volume 42.
* {{cite book
 | last = Cunningham | first = C. J. | date = 2001
 | title = The First Asteroid | publisher = Star Lab Press
 | isbn = 978-0-9708162-2-1 }}
* {{cite book
 |author1=Foderà Serio, G. |author2=Manara, A. |author3=Sicoli, P. |editor1=W. F. Bottke Jr. |editor2=A. Cellino |editor3=P. Paolicchi |editor4=R. P. Binzel |year=2002 | chapter=Giuseppe Piazzi and the Discovery of Ceres
 | title=Asteroids III | publisher=[[University of Arizona Press]]
 | pages=17–24 | location=Tucson, Arizona
 | chapter-url=http://www.lpi.usra.edu/books/AsteroidsIII/pdf/3027.pdf
 }}
* {{CathEncy| wstitle=Giuseppe Piazzi| first=William| last=Fox }}

==External links==
{{commons|Giuseppe Piazzi|Giuseppe Piazzi}}

* {{DBI |title= PIAZZI, Giuseppe |url=https://www.treccani.it/enciclopedia/giuseppe-piazzi_(Dizionario-Biografico)|last= Santaniello|first= Francesco|volume= 83}}
* [http://www.newadvent.org/cathen/12072d.htm Catholic Encyclopedia entry for Giuseppe Piazzi]
* [http://www.lpi.usra.edu/books/AsteroidsIII/pdf/3027.pdf Giuseppe Piazzi and the Discovery of Ceres]
* [http://digitalcollections.ucsc.edu/cdm/compoundobject/collection/p265101coll10/id/1487/rec/1 Portrait of Giuseppe Piazzi from the Lick Observatory Records Digital Archive, UC Santa Cruz Library's Digital Collections] {{Webarchive|url=https://web.archive.org/web/20160304200754/http://digitalcollections.ucsc.edu/cdm/compoundobject/collection/p265101coll10/id/1487/rec/1 |date=4 March 2016 }}

{{Authority control}}

{{DEFAULTSORT:Piazzi, Giuseppe}}
[[Category:1746 births]]
[[Category:1826 deaths]]
[[Category:People from the Province of Sondrio]]
[[Category:18th-century Italian astronomers]]
[[Category:Roman Catholic monks]]
[[Category:Discoverers of asteroids]]
[[Category:18th-century Italian Roman Catholic priests]]
[[Category:Theatines]]
[[Category:Ceres (dwarf planet)]]
[[Category:Fellows of the Royal Society]]
[[Category:Honorary members of the Saint Petersburg Academy of Sciences]]
[[Category:Catholic clergy scientists]]
[[Category:Academic staff of the University of Palermo]]
[[Category:Recipients of the Lalande Prize]]
[[Category:19th-century Italian astronomers]]