Story of unlucky French Astronomer

Guillaume Le Gentil

Guillaume Le Gentil was born on 12 September 1725 in France. This french astronomer is credited with discovery of several nebulae and was also elected to Royal Academy of Sciences, Paris. 

The lunar crater Le Gentil is named after him.

Le Gentil was commissioned by the French Academy of Sciences to observe the 1761 transit of Venus in front of the Solar Disk. He was asked to make this observation from Pondicherry, India (Pondicherry was in French possession at that time). This 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. Hundreds of observer astronauts were sent to different parts of earth for observing the transit which was expected to take place on 6 June 1761. Le Gentil started on a sea voyage from Paris in March 1760 for Pondicherry, India.

By July 1760 he reached Isle de France. Mauritius of today was called as Isle de France from 1715-1810, when the area was under French East India Company and part of France's empire. 

While the mission of Le Gentil was on its way there was a 'Seven Years' War' was also going on, which had started in 1756 and ended in 1763. This war was between the European Powers. This war hindered his way further east towards India. After a considerable delay he managed to secure his passage with a frigate for Pondicherry and started the jouney on March 1761. Due to some unfavorable winds the ship was thrown off-course and wasted five weeks wandering in sea. 

By the time ship of  Le Gentil reached Pondicherry, captain of ship learnt that Pondicherry is no longer a French occupation. British had defeated French in Pondicherry and captured it on 16 January 1761. Hence, the frigate was obliged to leave the ports. It started its journey back to Isle de France thereafter with all its crew, passengers and payload. 

On the day of transit of Venus, 6 June 1761 Le Gentil was on board the sailing ship. Due to the rolling of the ship, all observation made were unusable. It was a wasted effort so far.  

Having already completed the journey this far, Le Gentil decided to wait and plan for the next transition of the Venus for recording the observations. Next transition was to happen 8 years later. The transition happens in the pairs 8 years and each pair is separated from previous and next pairs by 243 years. 

Transition of Venus across the solar disk relative to earth

Determined not to miss the next one Le Gentil decided to remain in the Indian Ocean for several years, studying Madagascar and nearby islands. In 1766 he sailed to Manila to prepare for observing the 1769 transit. Manila at that time was the Spanish colony and Le Gentil could not get approval to stay and do his observations there. He sailed back to Pondicherry and reached there on March 1768, which was well before the date of transit. He built and observatory in Pondicherry and waited for the morning of  June 4, 1769, for which spent all these years away from his home.

At the time of the transition of Venus across the solar disk, from nowhere came the clouds and covered the whole view and remained there for the whole duration of transition. Le Gentil was extremely disappointed, he could not make any observations. It was a really bad luck for Le Gentil, he felt doomed. 

But he finally made it home in 1771 after being away for 11 years – only to find he had been declared legally dead. His spot in The Royal Academy of Sciences had been occupied. His wife had remarried and all his relatives had plundered his estate and was in shambles. Due to shipwrecks and wartime attacks, none of his letters had arrived to the Academy. It took an intervention from the King himself to restore his titles. He remarried and then lived up to the age of 67 years.