Joseph Jérôme Lefrançois de Lalande (; 11 July 1732 – 4April 1807) was a French

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

freemason Freemasonry (sometimes spelled Free-Masonry) consists of fraternal groups that trace their origins to the medieval guilds of stonemasons. Freemasonry is the oldest secular fraternity in the world and among the oldest still-existing organizati ...

and writer. He is known for having estimated a precise value of the

astronomical unit The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its m ...

(the distance from the

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

to the

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) using measurements of the

transit of Venus A transit of Venus takes place when Venus passes directly between the Sun and the Earth (or any other superior planet), becoming visible against (and hence obscuring a small portion of) the solar disk. During a transit, Venus is visible as ...

in 1769.

Biography

Lalande was born at

Bourg-en-Bresse Bourg-en-Bresse (; ) is the Prefectures in France, prefecture of the Ain department in the Auvergne-Rhône-Alpes region in Eastern France. Located northeast of Lyon, it is the capital of the ancient Provinces of France, province of Bresse (). I ...

(

département In the administrative divisions of France, the department (, ) is one of the three levels of government under the national level (" territorial collectivities"), between the administrative regions and the communes. There are a total of 101 ...

of Ain) to Pierre Lefrançois and Marie‐Anne‐Gabrielle Monchinet. His parents sent him to Paris to study law, but as a result of lodging in the Hôtel Cluny, where Joseph-Nicolas Delisle had his observatory, he was drawn to astronomy, and became the zealous and favoured pupil of both Delisle and

Pierre Charles Le Monnier Pierre Charles Le Monnier (; 20 November 1715 – 31 May 1799) was a French astronomer. His name is sometimes given as Lemonnier. Biography Le Monnier was born in Paris, where his father Pierre Lemonnier (physicist), Pierre (1675–1757), also ...

. Having completed his legal studies, he was about to return to Bourg to practise as an advocate, when Le Monnier obtained permission to send him to

Berlin Berlin ( ; ) is the Capital of Germany, capital and largest city of Germany, by both area and List of cities in Germany by population, population. With 3.7 million inhabitants, it has the List of cities in the European Union by population withi ...

, to make observations on the lunar

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

in concert with those of Nicolas Louis de Lacaille at the

Cape of Good Hope The Cape of Good Hope ( ) is a rocky headland on the Atlantic Ocean, Atlantic coast of the Cape Peninsula in South Africa. A List of common misconceptions#Geography, common misconception is that the Cape of Good Hope is the southern tip of Afri ...

Quarter of circle of Jonathan Sisson-MGR Lyon-IMG 9912

The successful execution of this task obtained for him, before he was twenty-one, admission to the Academy of Berlin, as well as his election as an adjunct astronomer to the

French Academy of Sciences The French Academy of Sciences (, ) is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific method, scientific research. It was at the forefron ...

. He now devoted himself to the improvement of the planetary theory, publishing in 1759 a corrected edition of

Edmond Halley Edmond (or Edmund) Halley (; – ) was an English astronomer, mathematician and physicist. He was the second Astronomer Royal in Britain, succeeding John Flamsteed in 1720. From an observatory he constructed on Saint Helena in 1676–77, Hal ...

's tables, with a history of

Halley's Comet Halley's Comet is the only known List of periodic comets, short-period comet that is consistently visible to the naked eye from Earth, appearing every 72–80 years, though with the majority of recorded apparitions (25 of 30) occurring after ...

whose return in that year he had helped

Alexis Clairaut Alexis Claude Clairaut (; ; 13 May 1713 – 17 May 1765) was a French mathematician, astronomer, and geophysicist. He was a prominent Newtonian whose work helped to establish the validity of the principles and results that Isaac Newton, Sir Isaa ...

and Nicole-Reine Lepaute to calculate. In 1762 Delisle resigned the chair of astronomy in the Collège de France in Lalande's favour. The duties were discharged by Lalande for forty-six years. His house became an astronomical seminary, and amongst his pupils were

Jean Baptiste Joseph Delambre Jean Baptiste Joseph, chevalier Delambre (19 September 1749 – 19 August 1822) was a French mathematician, astronomer, historian of astronomy, and geodesist. He was also director of the Paris Observatory, and author of well-known books on the ...

, Giuseppe Piazzi,

Pierre Méchain Pierre François André Méchain (; 16 August 1744 – 20 September 1804) was a French astronomer and surveyor who, with Charles Messier, was a major contributor to the early study of deep-sky objects and comets. Life Pierre Méchain was bo ...

, and his own nephew Michel Lefrançois de Lalande. By his publications in connection with the

of 1769 he won great fame. However, his difficult personality lost him some popularity. In 1766, Lalande, with Claude Adrien Helvétius, founded the ''Les Sciences'' lodge in Paris, and received its recognition from Grand Orient de France in 1772. In 1776, he changed its name to Les Neuf Soeurs, and arranged for

Benjamin Franklin Benjamin Franklin (April 17, 1790) was an American polymath: a writer, scientist, inventor, statesman, diplomat, printer, publisher and Political philosophy, political philosopher.#britannica, Encyclopædia Britannica, Wood, 2021 Among the m ...

to be chosen as the first worshipful master. Although his investigations were conducted with diligence rather than genius, Lalande's career was an eminent one. As a lecturer and writer he helped popularise astronomy. His planetary tables, into which he introduced corrections for mutual perturbations, were the best available up to the end of the 18th century. In 1801, he endowed the Lalande Prize, administered by the

, for advances in astronomy. Pierre-Antoine Véron, the young astronomer who for the first time in history determined the size of the Pacific Ocean from east to west, was Lalande's disciple. Lalande was an atheist, and wrote a dictionary of atheists with supplements that appeared in print posthumously. He never married. He was believed to have an illegitimate daughter Marie-Jeanne de Lalande whom he trained in mathematics so that she could help him with his work; according to more recent research she was not his daughter.

Near discovery of Neptune

In February 1847 Sears C. Walker of the US Naval Observatory was searching historical records and surveys for possible prediscovery sightings of the planet

Neptune Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...

that had been discovered the year before. He found that observations made by Lalande's nephew, Michel Lefrançois de Lalande in 1795 were in the direction of Neptune's position in the sky at that time and that Neptune might appear in the observation records. On 8 May and again on 10 May 1795 a ''star'' was observed and recorded with uncertainty noted on its position with a colon, this notation could also indicate an observing error so it was not until the original records of the observatory were reviewed that it was established with certainty that the object was Neptune and the position error between the two nights was due to the planet's motion across the sky. The discovery of these records of Neptune's position in 1795 led to a better calculation of the planet's orbit.

Awards and recognition

* In 1765, Lalande was elected a member of the

Royal Swedish Academy of Sciences The Royal Swedish Academy of Sciences () is one of the Swedish Royal Academies, royal academies of Sweden. Founded on 2 June 1739, it is an independent, non-governmental scientific organization that takes special responsibility for promoting nat ...

. * In 1781, he was elected a Foreign Honorary Member of the

American Academy of Arts and Sciences The American Academy of Arts and Sciences (The Academy) is one of the oldest learned societies in the United States. It was founded in 1780 during the American Revolution by John Adams, John Hancock, James Bowdoin, Andrew Oliver, and other ...

. * His name is one of the 72 names inscribed on the Eiffel Tower. * The crater Lalande on the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

is named after him. * A high school in

is named after Lalande. This high school was awarded the Médaille de la Résistance in recognition of the wartime conduct of its teachers and pupils, a unique case among all schools in France.

Notable works

His published works include: *''Traité d'astronomie'' (1st Ed., 2 vols., 1764; 2nd Ed., 4 vols., 1771–1781; 3rd Ed., 3 vols., 1792) *'' Histoire céleste française'' (1801), giving the places of 47,390 stars *''Bibliographie astronomique'' (1803), with a history of astronomy from 1780 to 1802 *''Astronomie des dames'' (1785) *''Abrégé de navigation'' (1793)
''Voyage d'un françois en Italie''
(1769), a valuable record of his travel in 1765–1766.
''Journal d'un voyage en Angleterre''
(1763

He communicated more than one hundred and fifty papers to the

, edited the ''Connoissance de temps'' (1759–1774), and again (1794–1807), and wrote the concluding two volumes of the 2nd edition of Montucla's ''Histoire des mathématiques'' (1802).

Publications

* * *

Notes

References

* * * * * Attribution *

External links

* /commons.wikimedia.org/w/index.php?title=File:Astronomie,_Tome_Premier.pdf Tome premier de ''Traité d'astronomie'', de 1764
Abrégé de navigation (pdf)

Portrait of Jerome Lalande from the Lick Observatory Records Digital Archive, UC Santa Cruz Library's Digital Collections

Joseph Jérôme Le Français de Lalande letters to Mme. Dupiery, MSS 530
a
L. Tom Perry Special Collections

Brigham Young University Brigham Young University (BYU) is a Private education, private research university in Provo, Utah, United States. It was founded in 1875 by religious leader Brigham Young and is the flagship university of the Church Educational System sponsore ...

Letters from baron de Franz Xaver von Zach to Joseph Jérôme Lefrançois de Lalande
(1792-1806) at th
digital library

Paris Observatory The Paris Observatory (, ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world. Its historic building is on the Left Ban ...

{{DEFAULTSORT:Lalande, Jerome Lefrancais De 1732 births 1807 deaths 18th-century French astronomers 19th-century French astronomers Burials at Père Lachaise Cemetery Fellows of the American Academy of Arts and Sciences Fellows of the Royal Society French atheists French Freemasons Honorary members of the Saint Petersburg Academy of Sciences Les Neuf Sœurs Members of the French Academy of Sciences Members of the Prussian Academy of Sciences Members of the Royal Swedish Academy of Sciences Writers from Bourg-en-Bresse