He began attending the private boarding school in Valence d'Agen, but he was very aware that his parents were making considerable sacrifices both in terms of paying for his education and also for not having his assistance in the fields. He began learning Latin and his performance in all his subjects was excellent.
Graduating from the school in Valence d'Agen he began his studies at the University of Toulouse obtaining his Bachelor of Science degree from that university in 1870. He received two further degrees: in physics in 1874, and in mathematics in 1876. During this time, he taught at a boarding school to finance his studies.
He caught the attention of one of his teachers, Félix Tisserand, and was appointed by him in 1877 to the post of assistant astronomer at the Toulouse Observatory, after he had graduated from the École d'Astronomie in Paris. Here he was put in charge of the meridian instrument. Tisserand was made Director of the Paris Observatory, bringing Bigourdan to Paris with him in 1879. In Paris, Bigourdan had the opportunity to take charge of the great equatorial telescope. In addition to other work that he was undertaking, he worked on his doctoral thesis which he submitted in 1886. He was awarded the degree for his thesis Sur l'équation personnelle dans les mesures d'étoiles doubles Ⓣ in which he studied measurements of 2800 double stars. It was at the Paris Observatory that he spent many years verifying the positions of 6380 nebulae. It was his aim to determine by visual observations the accurate positions of all the known nebulae of the northern hemisphere. He wanted to set a basis for future studies of the 'proper motion' of nebulae. This turned out to be in vain since distant nebulae will not show any proper motion. Percy MacMahon, in his Gold Medal address , explains that Bigourdan:-
... had before him in 1884 a mass of catalogues and separate memoirs concerning nebulae. Many of the observations that had been recorded had no pretensions to precision in measurement. Some that were precise according to views held in regard to precision at the time they were made could not be regarded as such at the present day. He gives a list of observations which may be regarded as being more or less precise. ... The list contains about 150 names. He also found that as the observations had been made by telescopes involving a wide range of optical power, it was difficult to compare the objects observed or even broadly to classify them. Further, many of the nebulae had not been re-observed for a great many years, and then only with instruments of small power. He therefore resolved in 1884 to observe the whole of the nebulae visible in the latitude of Paris with the equatorial of 0.31 m. aperture installed in the Paris Observatory. ... The Medallist's labours of observation terminated after twenty-five years in 1909, when 6380 nebulae had been duly recorded.Despite the impossible aim of detecting proper motion, his list of achievements while in Paris is not short. He discovered his only asteroid, 390 Alma in 1894; he identified around 500 new objects; his observations were published in 5 volumes of the Annales of the Paris Observatory occupying no fewer than 3000 pages. He also included a history of the discoveries and previous observations of the nebulae he worked on.
Bigourdan was also a participant in expeditions. In June 1882, he took part in the observations of the transit of Venus on the island of Martinique. While away, his brother died of typhoid fever. In the same year, he built a four-roomed house in Tujague. In 1883, he left for St Petersburg, stopping in Kraków in Poland, visited Berlin and Vienna. He also went to Joal, Senegal in 1892 to observe the total eclipse of the Sun which took place on 16 April 1893. A report of the expedition records :-
Aside from photographs of the corona with several short cameras, which were successful, the observations were wholly spectroscopic. The spectrum of the corona was photographed as far up in the ultra-violet as the ordinary solar spectrum extends, and at least fifteen new coronal and chromospheric bright lines were detected. The light of the corona consisted of a strong continuous spectrum and bright lines. None of the ordinary solar dark lines were observed.On this same expedition, he made a determination of the value of gravity at Joal. He did this again in 1896, but atop Mont Blanc. Moreover, he travelled to Hellín, Spain in 1900 and Tunis, Tunisia in 1905 also to view solar eclipses.
In 1902, working with his colleague Henri Renan from the Paris Observatory, and Frank W Dyson (1868-1939), Henry Park Hollis (1858-1939) and others from the Greenwich Observatory, he participated in an attempt to re-determine with a greater precision the longitudinal difference between London and Paris. Bigourdan made the first of two series of observations between 18 April 1902 and 29 June 1902. Both Greenwich and Paris Observatories used meridian instruments built by the English instrument makers Troughton & Simms. The first task carried out by Bigourdan was to examine the operation of the instruments. He wrote to Henri Poincaré about his :-
... study of the influence of the inclination of the axis of rotation of the telescope. This inclination is determined using the level and by observation of the reflected image on a mercury bath (determination of the collimation by reversals on a test pattern, on the mercury bath and on circumpolar stars). Bigourdan noticed imperfections in his measuring device. Above all, the level which serves to determine the inclination showed, in the size of its parts, a direct variability with the temperature. Bigourdan therefore studied the behaviour of the level in order to be able to correct the readings made in the longitude operations. He found that the metal mount on the level vial, "still used quite often, especially abroad," was responsible for the dilation.Félix Tisserand, the Director of the Paris Observatory, died in 1896 and Maurice Loewy (1833-1907), was appointed to succeed him as Director. Loewy, born in Vienna, had been an assistant at the Vienna Observatory but, being a Jew, could not advance to a senior position. He had moved to France, working at the Paris Observatory from 1860. When he died on 15 October 1907 the Observatory began the process of appointing a new Director. The appointment was made by the Minister after receiving advice from the Academy of Sciences and the Council of the Observatory. There were several candidates but the close call came between Bigourdan and Benjamin Baillaud. Both were members of the Academy of Sciences but Bigourdan was a full member while Baillaud was only a corresponding member. Bigourdan had worked at the Paris Observatory for 28 years and regularly attended meetings of the Academy of Sciences. Henri Poincaré considered Bigourdan a collaborator and even informed Baillaud that he intended to vote for Bigourdan. There was no doubt that Bigourdan had produced the greater amount of research but Baillaud had the most experience as an administrator and had achieved great things in this capacity. First one man and then the other appeared to be first choice. Both wrote to the Minister defending themselves from criticism they were receiving. Bigourdan wrote on 23 December 1907 saying, "some accuse me of being capable of acts of intolerance", and defended himself from that accusation. On 17 December 1907 some newspapers had reported, prematurely, that Bigourdan had almost certainly won but when the official announcement came on 6 January 1908 it was Baillaud who was declared the new Director of the Paris Observatory.
Bigourdan also held a keen interest in the transmission of time signals by wireless. In 1911, France switched from a time zone centred at Paris to one centred at Greenwich, London and Bigourdan helped establish the new time zone. After conferences in Paris in 1912 and 1913, the International Time Service was founded, with a bureau in Paris of which Bigourdan was given the directorship. After the First World War, Bigourdan remained director keeping in close touch with Benjamin Baillaud and General Ferrié, other figureheads in the time-keeping spheres of interest.
Bigourdan was recognised for his work and achievements in the form of titles and awards. He was awarded his first Lalande Prize from the Academy of Sciences in 1883 for the work he had done in Martinique, as one of a group of nine, each winning 540 francs. His second Lalande Prize was awarded solely to him, and was given in 1891. The year 1895 saw him make Knight of the Legion of Honour, becoming an Officer in 1919. He won the Valz Prize, awarded by the French Academy of Sciences, in 1886. The Royal Astronomical Society granted him their Gold Medal in 1919. This year also saw him receive the Prix Jules-Janssen, the highest award of the French Astronomical Society.
He was also a member of multiple scientific societies, and held many important roles: he became a member of the Bureau des Longitudes in 1903 and worked to enrich their Annuaire with notices of interesting researches in current astronomy, such as determinations of parallax and classification of stellar spectra; also in 1903, he was elected an Associate of the Royal Astronomical Society; 1904 saw him become a member of the French Academy of Sciences, becoming vice-president in 1923. From its commencement in 1919, Bigourdan served as director of the Bureau International de l'Heure. In 1924, he was made President of the Academy of Sciences and the Institute of France.
Bigourdan was responsible for ensuring that various works were published, for example, that of A G Pingré's Annales célestes du dix-septiéme siècle Ⓣ. The manuscript had been completed in 1791, and a start had been made on its publication, continuing slowly until Pingré's death, whereupon it stopped. The manuscript was lost, before being found by Bigourdan at the Paris Observatory under an incorrect title. Under the auspices of the French Academy of Sciences, these Annales were printed in 1901. After he retired in 1928 from the Bureau de l'Heure, he gave, in the Annuaire, a history of the Bureau de Longitudes, the fourth part of which was published in 1932, only a short while before his death. This was certainly not his first historical work for he had published The first learned societies of Paris in the seventeenth century: and the origins of the Academy of Science (1918) and History of observational astronomy and observatories in France (3 volumes) (1918). In fact his publication record is remarkable for, over 45 years, he wrote 540 articles which is an average of an article per month.
Bigourdan has been credited with a method for adjusting equatorial mount telescopes. Bigourdan's Method allows the setting up of a telescope mount when one cannot locate the celestial pole and does not know the latitude of the place. Precision is high, but it takes a lot of adjustment time.
In February 1885, he married Marie Mélanie Sophie Mouchez, the eldest daughter of Admiral Amédée Mouchez, then the director of the Paris Observatory. Together, they had 9 children. Up until 1913, the whole Bigourdan family came to Sistels on vacation, even including Mouchez cousins. After this, the outbreak of war and the Parisian environment made his wife and children no longer go to Tujague. They got bored on this old farm, in the countryside; Guillaume Bigourdan, however, came alone every summer to spend a few weeks. During his stays, he worked on cultivating his land, went to see his former classmates and spoke with them only in Occitan (a Romance language spoken in southern France), even when he gave lessons in astronomy.
He died in Paris in 1932 in his apartment at 6 rue Cassini, near the Observatory. His funeral was held in the presence of many scientists, but without any government representative; he was buried in the Montparnasse cemetery.
Article by: I J Falconer, J G Mena, J J O'Connor, T S C Peres, E F Robertson, University of St Andrews.