Jean-Philippe Loys de Cheseaux (; 4 May 1718 – 30 November 1751) was a Swiss

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, natural satellite, moons, comets and galaxy, g ...

Biography

Loys de Cheseaux was born on 4 May 1718 in

Lausanne , neighboring_municipalities= Bottens, Bretigny-sur-Morrens, Chavannes-près-Renens, Cheseaux-sur-Lausanne, Crissier, Cugy, Écublens, Épalinges, Évian-les-Bains (FR-74), Froideville, Jouxtens-Mézery, Le Mont-sur-Lausanne, Lugrin (FR-74), ...

Vaud Vaud ( ; french: (Canton de) Vaud, ; german: (Kanton) Waadt, or ), more formally the canton of Vaud, is one of the 26 cantons forming the Swiss Confederation. It is composed of ten districts and its capital city is Lausanne. Its coat of arms b ...

, to Paul-Etienne Loys de Cheseaux, a

banneret A knight banneret, sometimes known simply as banneret, was a medieval knight ("a commoner of rank") who led a company of troops during time of war under his own banner (which was square-shaped, in contrast to the tapering standard or the penn ...

, and Estienne-Judith de Crousaz. His brother was Charles-Louis Loys de Cheseaux. He was educated by his maternal grandfather, the mathematician and philosopher

Jean-Pierre de Crousaz Jean-Pierre de Crousaz (13 April 166322 March 1750) was a Swiss theologian and philosopher. He is now remembered more for his letters of commentary than his formal works. Life De Crousaz was born in Lausanne, Switzerland. He was a many-sided man, ...

, and wrote his first essays, under the title ''Essais de Physique'', in 1735, aged 17. In 1736, Loys de Cheseaux installed an observatory in his father's lands in

Cheseaux-sur-Lausanne Cheseaux-sur-Lausanne (, literally ''Cheseaux on Lausanne''; frp, Chesâls) is a municipality in the district of Lausanne in the canton of Vaud in Switzerland. It is a suburb of the city of Lausanne. History Cheseaux-sur-Lausanne is first ment ...

. He acquired a reputation in Europe as an astronomer with the publication of his ''Traité de la Comète'', in 1744, a treatise on his observations of the comet

C/1743 X1 The Great Comet of 1744, whose official designation is C/1743 X1, and which is also known as Comet de Chéseaux or Comet Klinkenberg-Chéseaux, was a spectacular comet that was observed during 1743 and 1744. It was discovered independently in lat ...

in which he also became one of the first to state, in its modern form, what would later be known as

Olbers' paradox Olbers's paradox, also known as the dark night sky paradox, is an argument in astrophysics and physical cosmology that says that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe. In the hyp ...

(that, if the

universe The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. Acc ...

is infinite, the night sky should be bright). After his discovery of C/1743 (along with

Dirk Klinkenberg Dirk Klinkenberg (15 November 1709, Haarlem – 3 March 1799, The Hague) was secretary of the Dutch government for 40 years. He was also known as a mathematician and amateur astronomer. Jan de Munck, Dirk Klinkenberg, and Jean-Philippe de Chese ...

), Loys de Cheseaux discovered the comet C/1746 P1. In 1746, he presented a list of

nebula A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regio ...

e, eight of which were his own new discoveries, to the

French Academy of Sciences The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV of France, Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific me ...

. The list was noted privately by

Le Gentil Guillaume Joseph Hyacinthe Jean-Baptiste Le Gentil de la Galaisière (, 12 September 1725 – 22 October 1792) was a French astronomer who discovered several nebulae and was appointed to the Royal Academy of Sciences. He made unsuccessful attemp ...

in 1759, but only made public in 1892 by

Guillaume Bigourdan Camille Guillaume Bigourdan (; 6 April 1851 – 28 February 1932) was a French astronomer. Personal life Bigourdan was born at Sistels, Tarn-et-Garonne to Pierre Bigourdan and Jeanne Carrière. When his teachers and local curate recognised ...

. From 1747, Loys de Cheseaux was a corresponding member of the science academies of

Göttingen Göttingen (, , ; nds, Chöttingen) is a college town, university city in Lower Saxony, central Germany, the Capital (political), capital of Göttingen (district), the eponymous district. The River Leine runs through it. At the end of 2019, t ...

St. Petersburg Saint Petersburg ( rus, links=no, Санкт-Петербург, a=Ru-Sankt Peterburg Leningrad Petrograd Piter.ogg, r=Sankt-Peterburg, p=ˈsankt pʲɪtʲɪrˈburk), formerly known as Petrograd (1914–1924) and later Leningrad (1924–1991), i ...

, Stockholm, as well as the Academy of Sciences of Paris and the

Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...

of London. He was offered the post of director of the St. Petersburg observatory, but declined the invitation. In 1751, Loys de Cheseaux travalled to Paris and was presented to the Academy of Sciences. There he died, after a short illness, on 30 November 1751, aged 33. In addition to astronomy, Loys de Cheseaux researched

Biblical chronology The chronology of the Bible is an elaborate system of lifespans, 'generations', and other means by which the Masoretic Hebrew Bible (the text of the Bible most commonly in use today) measures the passage of events from the creation to around 164 ...

, calculating the movements of the Sun and Moon relative to descriptions in the

Book of Daniel The Book of Daniel is a 2nd-century BC biblical apocalypse with a 6th century BC setting. Ostensibly "an account of the activities and visions of Daniel, a noble Jew exiled at Babylon", it combines a prophecy of history with an eschatology (a ...

and the occurrence of

solstices A solstice is an event that occurs when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around June 21 and December 21. In many countrie ...

and

equinoxes A solar equinox is a moment in time when the Sun crosses the Earth's equator, which is to say, appears directly above the equator, rather than north or south of the equator. On the day of the equinox, the Sun appears to rise "due east" and set ...

Jerusalem Jerusalem (; he, יְרוּשָׁלַיִם ; ar, القُدس ) (combining the Biblical and common usage Arabic names); grc, Ἱερουσαλήμ/Ἰεροσόλυμα, Hierousalḗm/Hierosóluma; hy, Երուսաղեմ, Erusałēm. i ...

at the time of the

Old Testament The Old Testament (often abbreviated OT) is the first division of the Christian biblical canon, which is based primarily upon the 24 books of the Hebrew Bible or Tanakh, a collection of ancient religious Hebrew writings by the Israelites. The ...

story. In his ''Dissertation Chronologique'' (1748), Loys de Cheseaux tried to establish the date of the

eclipse An eclipse is an astronomical event that occurs when an astronomical object or spacecraft is temporarily obscured, by passing into the shadow of another body or by having another body pass between it and the viewer. This alignment of three ce ...

known as "

crucifixion darkness The crucifixion darkness is an episode in three of the canonical gospels in which the sky becomes dark in daytime during the crucifixion of Jesus for roughly three hours. Most ancient and medieval Christian writers treated this as a miracle, and ...

" in order to determine the date of the

crucifixion of Jesus The crucifixion and death of Jesus occurred in 1st-century Judea, most likely in AD 30 or AD 33. It is described in the four canonical gospels, referred to in the New Testament epistles, attested to by other ancient sources, and consid ...

References

Works

Loys de Cheseaux, Jean Philippe de – Remarques astronomiques sur le livre de Daniel, 1777 – BEIC 786685

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External links

Short biography
at

SEDS Students for the Exploration and Development of Space (SEDS) is a non-profit international student organization whose purpose is to drive space advocacy of space exploration and development through educational and engineering projects. Histo ...

De Cheseaux's List of 21 "Nebulae"
at SEDS 1718 births 1751 deaths People from Lausanne 18th-century Swiss astronomers Swiss nobility Discoverers of comets {{Europe-astronomer-stub