20th-century French astronomers

Evry Léon Schatzman (16 September 1920 – 25 April 2010) was a French scientist hailed as "the father of modern French astrophysics".

Maurice Théodore Adolphe Hamy (31 October 1861, Boulogne-sur-Mer – 9 April 1936, Paris) was a French astronomer.
He obtained in 1887 a doctorate from the Faculté des sciences de Paris with dissertation Étude sur la figure des corps célestes. In the 1890s he applied his method of interference fringes to an analysis of errors made in astronomical observations using meridian circles. He used his interference method to confirm Barnard's measurement of the apparent diameter of Venus. Hamy participated in the creation of l'Institut d'optique théorique et appliquée (SupOptique).
He won the prix Lalande in 1895. Filling the empty chair created by the death of Jules Janssen, Hamy was elected in 1908 a member of l'Académie des sciences and then in 1928 its president. He was also elected a member of the Bureau des longitudes.
He is a nephew of Ernest Hamy.

François Gonnessiat (May 22, 1856 (Nurieux-Volognat)–October 18, 1934) was a French astronomer, observer of comets and discoverer of two minor planets.He worked at the Observatory of Lyon. In 1889 he won the Lalande Prize for astronomy from the French Academy of Sciences; 1901 became director of the Quito (Ecuador) Observatory for the purpose of making geodetic measurements. He became a well known and respected member of the academic scene of the city, where a street is named after him. From 1908 to 1931, he was director of the Algiers Observatory where one of his colleagues was Benjamin Jekhovsky. He was also director of the Quito Astronomical Observatory.The asteroid 1177 Gonnessia was named in his memory (H 109).

Louis Fabry was a French astronomer who was born in Marseille, April 20, 1862, and died in Les Lecques, January 26, 1939.

Jean François Chazy (15 August 1882, Villefranche-sur-Saône – 9 March 1955, Paris) was a French mathematician and astronomer.

Roger Victor Émile Cayrel (4 December 1925 – 11 January 2021) was a French astronomer. His main interests were stellar atmospheres, galactic chemical evolution and metal-poor stars.

Jean Bosler (24 March 1878, Angers – 25 September 1973, Marseille) was a French astronomer and author of several books.
Recruited by Deslandres as an astronomer at l’observatoire de Paris, Bosler discovered in 1908 in the spectrum of Comet Morehouse the spectral lines of ionized nitrogen, which was the first evidence of that element in comets. Much of his research was on the physical properties and orbits of comets. He made a report on progress in astrophysics in the United States for the 1910 annual report of the Smithsonian Institution. In 1912, he showed in his doctoral dissertation (supervised by Henri Poincaré) that the Sun’s magnetic field, by means of the intermediary of the solar wind, explains many aspects of cometary tails, the aurora borealis and aurora australis, solar storms and telluric currents. During a solar eclipse in 1914, Bosler observed in the corona a spectral band “nouvelle, intense et unique” which he suggested was spectral evidence for coronium; however, in the 1930s subsequent research showed that the cause was a highly ionized form of iron. In 1916, he published an analysis of the circular form of lunar craters as caused by the impact of meteors.
In 1923 Bosler was named director of Marseille Observatory, a post he occupied until his retirement in 1948. Simultaneously with his directorship, he taught at the University of Marseille from 1923 to 1948. Bosler made important contributions to the theory of the evolution of stars and published the first textbook in French that dealt with the then recent discoveries of Hubble and the work on optical phenomena of such physicists as Michelson, Fabry and Perot.
Bosler won the Prix Jules Janssen in 1911 from the Société astronomique de France, the French astronomical society, and the Prix Lalande from l'Académie des sciences in 1913.
He came from the French branch of the Hessian family Boßler.Books

Les théories modernes du soleil (1910)
L’évolution des étoiles (1923)
Cours d’astronomie (1928)

Antoine Émile Henry Labeyrie (born 12 May 1943) is a French astronomer, who held the Observational astrophysics chair at the Collège de France between 1991 and 2014, where he is currently professor emeritus. He is working with the Hypertelescope Lise association, which aims to develop an extremely large astronomical interferometer with spherical geometry that might theoretically show features on Earth-like worlds around other suns, as its president. He is a member of the French Academy of Sciences in the Sciences of the Universe (sciences de l'univers) section. Between 1995 and 1999 he was director of the Haute-Provence Observatory.
Labeyrie graduated from the "grande école" SupOptique (École supérieure d'optique). He invented speckle interferometry, and works with astronomical interferometers. Labeyrie concentrated particularly on the use of "diluted optics" beam combination or "densified pupils" of a similar type but larger scale than those Michelson used for measuring the diameters of stars in the 1920s, in contrast to other astronomical interferometer researchers who generally switched to pupil-plane beam combination in the 1980s and 1990s.
The main-belt asteroid 8788 Labeyrie (1978 VP2) is named in honor of Antoine Émile Henry Labeyrie and Catherine Labeyrie. In 2000, he was awarded The Benjamin Franklin Medal.

Théophile Moreux (20 November 1867 – 13 July 1954) was a French astronomer and meteorologist.

Catherine Jeanne Cesarsky (born Catherine Jeanne Gattegno on 24 February 1943) is an Argentine and French astronomer, known for her research activities in astrophysics and for her leadership in astronomy and atomic energy. She is the current chairperson of the Square Kilometre Array's governing body, SKAO Council. She was the first female president of the International Astronomical Union (2006-2009) and the first female director general of the European Southern Observatory (1999-2007).