Guillaume Le Gentil
Encyclopedia
Guillaume Joseph Hyacinthe Jean-Baptiste Le Gentil de la Galaisière (Coutances, September 12, 1725 – Paris, October 22, 1792) was a French astronomer
.
and first intended to enter the church before turning to astronomy. He discovered what are now known as the Messier object
s M32, M36
and M38
, as well as the nebulosity in M8
, and he was the first to catalogue the dark nebula sometimes known as Le Gentil 3 (in the constellation
Cygnus
).
He was part of the international collaborative project to measure the distance to the Sun, by observing the transit of Venus
at different points on the earth.
Edmond Halley
had suggested the idea, but it required careful measurements from different places on earth, and the project was launched with more than a hundred observers dispatched to different parts of the globe, for observing the transit coming up in 1761. The French expedition turned out to be particularly unlucky, and perhaps the most unfortunate was Guillaume le Gentil, who set out for Pondicherry, a French colony in India
.
He set out from Paris in March 1760, and reached Île de France (Mauritius
) in July. But having learned that war
had broken out between France
and Britain
, and deeming it dangerous to try to reach Pondicherry, he determined to go elsewhere; a frigate was bound for India's Coromandel Coast
, and he sailed in March 1761. When they had nearly arrived they learned that the British had occupied Pondicherry, so the frigate was obliged to return to Île de France. June 6, the day of the transit, came, and the sky was clear, but he could not take astronomical observations with the vessel rolling about. After having come this far, he thought he might as well await the next transit of Venus, which would come in another eight years (they are relatively infrequent, occurring in pairs 8 years apart, but each such pair is separated from the previous and next pairs by more than a century.)
After spending some time mapping the eastern coast of Madagascar
, he decided to record the 1769 transit from Manila
in the Philippines
. Encountering hostility from the Spanish authorities there, he headed back to Pondicherry, which had been restored to France by peace treaty in 1763, where he arrived in March 1768. He built a small observatory and waited patiently. At last, the day in question (June 4, 1769) arrived, but although the mornings in the preceding month had all been lovely, on this day the sky became overcast, and Le Gentil saw nothing. The misfortune drove him to the brink of insanity, but at last he recovered enough strength to return to France.
The return trip was first delayed by dysentery
, and further when his ship was caught in a storm and dropped him off at Île Bourbon (Réunion
), where he had to wait until a Spanish ship took him home. He finally arrived in Paris eleven years later in October 1771, only to find that he had been declared legally dead and been replaced in the Royal Academy of Sciences. His wife had remarried, and all his relatives had "enthusiastically plundered his estate". Lengthy litigation and the intervention of the king were ultimately required before things were normalized. He got back his seat in the academy, remarried, and lived apparently happily for another 21 years.
One of his interesting findings was that the duration of the lunar eclipse
of 30 August 1765 was predicted by a Tamil
astronomer, based on the computation of the size and extent of the earth-shadow (going back to Aryabhata
, 5th c.), and was found short by 41 seconds, whereas the charts of Tobias Mayer were long by 68 seconds.
. Transit of Venus
was first produced at the Manitoba Theatre Centre
in 1992. It was subsequently made into an opera of the same name
with music by Victor Davies, presented by Manitoba Opera
in 2007.
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
.
Biography
He was born in CoutancesCoutances
Coutances is a commune in the Manche department in Normandy in north-western France.-History:Capital of the Unelli, a Gaulish tribe, the town took the name of Constantia in 298 during the reign of Roman emperor Constantius Chlorus...
and first intended to enter the church before turning to astronomy. He discovered what are now known as the Messier object
Messier object
The Messier objects are a set of astronomical objects first listed by French astronomer Charles Messier in 1771. The original motivation of the catalogue was that Messier was a comet hunter, and was frustrated by objects which resembled but were not comets...
s M32, M36
Messier 36
Open Cluster M36 is an open cluster in the Auriga constellation. It was discovered by Giovanni Batista Hodierna before 1654. M36 is at a distance of about 4,100 light years away from Earth and is about 14 light years across. There are at least sixty members in the cluster...
and M38
Messier 38
Messier 38 is an open cluster in the Auriga constellation.It was discovered by Giovanni Batista Hodierna before 1654 and independently found by Le Gentil in 1749...
, as well as the nebulosity in M8
Lagoon Nebula
The Lagoon Nebula is a giant interstellar cloud in the constellation Sagittarius. It is classified as an emission nebula and as an H II region....
, and he was the first to catalogue the dark nebula sometimes known as Le Gentil 3 (in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Cygnus
Cygnus (constellation)
Cygnus is a northern constellation lying on the plane of the Milky Way. Its name is the Latinized Hellenic word for swan. One of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross...
).
He was part of the international collaborative project to measure the distance to the Sun, by observing the transit of Venus
Transit of Venus
A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth, becoming visible against the solar disk. During a transit, Venus can be seen from Earth as a small black disk moving across the face of the Sun...
at different points on the earth.
Edmond Halley
Edmond Halley
Edmond Halley FRS was an English astronomer, geophysicist, mathematician, meteorologist, and physicist who is best known for computing the orbit of the eponymous Halley's Comet. He was the second Astronomer Royal in Britain, following in the footsteps of John Flamsteed.-Biography and career:Halley...
had suggested the idea, but it required careful measurements from different places on earth, and the project was launched with more than a hundred observers dispatched to different parts of the globe, for observing the transit coming up in 1761. The French expedition turned out to be particularly unlucky, and perhaps the most unfortunate was Guillaume le Gentil, who set out for Pondicherry, a French colony in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
.
He set out from Paris in March 1760, and reached Île de France (Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...
) in July. But having learned that war
Seven Years' War
The Seven Years' War was a global military war between 1756 and 1763, involving most of the great powers of the time and affecting Europe, North America, Central America, the West African coast, India, and the Philippines...
had broken out between France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
and Britain
Kingdom of Great Britain
The former Kingdom of Great Britain, sometimes described as the 'United Kingdom of Great Britain', That the Two Kingdoms of Scotland and England, shall upon the 1st May next ensuing the date hereof, and forever after, be United into One Kingdom by the Name of GREAT BRITAIN. was a sovereign...
, and deeming it dangerous to try to reach Pondicherry, he determined to go elsewhere; a frigate was bound for India's Coromandel Coast
Coromandel Coast
The Coromandel Coast is the name given to the southeastern coast of the Indian Subcontinent between Cape Comorin and False Divi Point...
, and he sailed in March 1761. When they had nearly arrived they learned that the British had occupied Pondicherry, so the frigate was obliged to return to Île de France. June 6, the day of the transit, came, and the sky was clear, but he could not take astronomical observations with the vessel rolling about. After having come this far, he thought he might as well await the next transit of Venus, which would come in another eight years (they are relatively infrequent, occurring in pairs 8 years apart, but each such pair is separated from the previous and next pairs by more than a century.)
After spending some time mapping the eastern coast of Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
, he decided to record the 1769 transit from Manila
Manila
Manila is the capital of the Philippines. It is one of the sixteen cities forming Metro Manila.Manila is located on the eastern shores of Manila Bay and is bordered by Navotas and Caloocan to the north, Quezon City to the northeast, San Juan and Mandaluyong to the east, Makati on the southeast,...
in the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
. Encountering hostility from the Spanish authorities there, he headed back to Pondicherry, which had been restored to France by peace treaty in 1763, where he arrived in March 1768. He built a small observatory and waited patiently. At last, the day in question (June 4, 1769) arrived, but although the mornings in the preceding month had all been lovely, on this day the sky became overcast, and Le Gentil saw nothing. The misfortune drove him to the brink of insanity, but at last he recovered enough strength to return to France.
The return trip was first delayed by dysentery
Dysentery
Dysentery is an inflammatory disorder of the intestine, especially of the colon, that results in severe diarrhea containing mucus and/or blood in the faeces with fever and abdominal pain. If left untreated, dysentery can be fatal.There are differences between dysentery and normal bloody diarrhoea...
, and further when his ship was caught in a storm and dropped him off at Île Bourbon (Réunion
Réunion
Réunion is a French island with a population of about 800,000 located in the Indian Ocean, east of Madagascar, about south west of Mauritius, the nearest island.Administratively, Réunion is one of the overseas departments of France...
), where he had to wait until a Spanish ship took him home. He finally arrived in Paris eleven years later in October 1771, only to find that he had been declared legally dead and been replaced in the Royal Academy of Sciences. His wife had remarried, and all his relatives had "enthusiastically plundered his estate". Lengthy litigation and the intervention of the king were ultimately required before things were normalized. He got back his seat in the academy, remarried, and lived apparently happily for another 21 years.
One of his interesting findings was that the duration of the lunar eclipse
Lunar eclipse
A lunar eclipse occurs when the Moon passes behind the Earth so that the Earth blocks the Sun's rays from striking the Moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a...
of 30 August 1765 was predicted by a Tamil
Tamil people
Tamil people , also called Tamils or Tamilians, are an ethnic group native to Tamil Nadu, India and the north-eastern region of Sri Lanka. Historic and post 15th century emigrant communities are also found across the world, notably Malaysia, Singapore, Mauritius, South Africa, Australia, Canada,...
astronomer, based on the computation of the size and extent of the earth-shadow (going back to Aryabhata
Aryabhata
Aryabhata was the first in the line of great mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy...
, 5th c.), and was found short by 41 seconds, whereas the charts of Tobias Mayer were long by 68 seconds.
Play and opera
Le Gentil is the subject of a play by Canadian playwright Maureen HunterMaureen Hunter
Maureen Hunter is a Canadian playwright who lives in Winnipeg, Manitoba.She was born in Indian Head, Saskatchewan and graduated from the University of Saskatchewan. Transit of Venus was performed by the Royal Shakespeare Company and recorded by the BBC...
. Transit of Venus
Transit of Venus (play)
Transit of Venus is a play by Canadian playwright Maureen Hunter. It was first produced at the Manitoba Theatre Centre in November 1992.The play is based on the life of Guillaume Le Gentil , a gentleman astronomer....
was first produced at the Manitoba Theatre Centre
Manitoba Theatre Centre
Royal Manitoba Theatre Centre is Canada's oldest English-language regional theatre. Next to the Stratford and Shaw Festivals, MTC has a higher annual attendance than any other theatre in the country...
in 1992. It was subsequently made into an opera of the same name
Transit of Venus (opera)
Transit of Venus is an opera in three acts by Victor Davies. The English libretto is by Canadian playwright Maureen Hunter based on her play of the same name first produced at the Manitoba Theatre Centre in November 1992.-Roles:-Synopsis:...
with music by Victor Davies, presented by Manitoba Opera
Manitoba Opera
Manitoba Opera is an opera company in Winnipeg, Manitoba that was founded in 1969. Its first production was a concert of Giuseppe Verdi's Il Trovatore in 1972. Manitoba Opera is one of several western Canadian opera companies that flourished under the inspired leadership of Irving Guttman,...
in 2007.
Further reading
- Le Gentil's story is told in detail in Helen Sawyer Hogg, "Le Gentil and the Transits of Venus, 1761 and 1769", Journal of the Royal Astronomical Society of Canada, vol. 45 (1951), pp. 37–44, 89-92, 127-134 & 173-178 Out of Old Books.
- Le Gentil himself was the author of Voyage dans les mers de l'Inde, fait par ordre du Roi, à l'occasion du passage de Vénus, sur le disque du Soleil, le 6 juin 1761 & le 3 du même mois 1769 par M. Le Gentil, de l'académie royale des sciences. Imprimé par ordre de sa Majesté, two volumes, Paris 1779 and 1781.