Henri Alexandre Deslandres (24 July 1853 – 15 January 1948) was a French

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

, director of the

Meudon Meudon () is a municipality in the southwestern suburbs of Paris, France. It is in the département of Hauts-de-Seine. It is located from the center of Paris. The city is known for many historic monuments and some extraordinary trees. One of t ...

and Paris Observatories, who carried out intensive studies on the behaviour of the atmosphere of the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

Biography

Deslandres' undergraduate years at the

École Polytechnique École may refer to: * an elementary school in the French educational stages normally followed by secondary education establishments (collège and lycée) * École (river), a tributary of the Seine flowing in région Île-de-France * École, Savoi ...

were played out against the aftermath of the Franco-Prussian War and the chaos of the

Paris Commune The Paris Commune (french: Commune de Paris, ) was a revolutionary government that seized power in Paris, the capital of France, from 18 March to 28 May 1871. During the Franco-Prussian War of 1870–71, the French National Guard had defended ...

so, on graduation in 1874, he responded to the continuing military tension with the emerging

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

by embarking on a military career. Rising to the rank of

captain Captain is a title, an appellative for the commanding officer of a military unit; the supreme leader of a navy ship, merchant ship, aeroplane, spacecraft, or other vessel; or the commander of a port, fire or police department, election precinct, e ...

in the engineers, he became increasingly interested in

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

and, in 1881, resigned his commission to join

Alfred Cornu Marie Alfred Cornu (; 6 March 1841 – 12 April 1902) was a French physicist. The French generally refer to him as Alfred Cornu. Life Cornu was born at Orléans to François Cornu and Sophie Poinsellier. He was educated at the École polytechni ...

's laboratory at the École Polytechnique, working on

spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...

. He continued his spectroscopic work at the

Sorbonne Sorbonne may refer to: * Sorbonne (building), historic building in Paris, which housed the University of Paris and is now shared among multiple universities. *the University of Paris (c. 1150 – 1970) *one of its components or linked institution, ...

, earning his doctorate in 1888 and created the

deslandres table In electronic spectroscopy, constructing a Deslandres table is a useful method to assign vibronic transitions. In such a table, the frequencies of the lines seen in an electronic spectrum of a molecule are collected so that the differences in e ...

, which finds numerical patterns in

spectral line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...

s that paralleled the work of

Johann Balmer Johann Jakob Balmer (1 May 1825 – 12 March 1898) was a Swiss mathematician best known for his work in physics, the Balmer series of hydrogen atom. Biography Balmer was born in Lausen, Switzerland, the son of a chief justice also named Johan ...

and were to catalyse the development of

quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...

in the 20th century. In 1868,

Pierre Janssen Pierre Jules César Janssen (22 February 1824 – 23 December 1907), usually known as Jules Janssen, was a French astronomer who, along with English scientist Joseph Norman Lockyer, is credited with discovering the gaseous nature of the solar ...

's solar observations had led him to report to the

Académie des Sciences The French Academy of Sciences (French: ''Académie des 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 research. It was at the ...

that ''It is no longer geometry and mechanics which dominate n astronomybut physics and chemistry.'' Such advice was sternly rejected by director of the

Paris Observatory The Paris Observatory (french: Observatoire de Paris ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centers in the world. Its histor ...

Urbain Le Verrier Urbain Jean Joseph Le Verrier FRS (FOR) HFRSE (; 11 March 1811 – 23 September 1877) was a French astronomer and mathematician who specialized in celestial mechanics and is best known for predicting the existence and position of Neptune using ...

and the French government awarded Janssen a grant to establish an astrophysical observatory at

on the outskirts of

Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. S ...

with Janssen as the sole astronomer. In 1889, Le Verrier was succeeded by

Amédée Mouchez Ernest Amédée Barthélemy Mouchez (24 August 1821 – 29 June 1892) was a French naval officer who became director of the Paris Observatory and launched the ill-fated ''Carte du Ciel'' project in 1887. Life Born in Madrid, Spain, Mouchez emba ...

who set to work to bring astrophysics into the mainstream by hiring Deslandres. Deslandres developed the

spectroheliograph The spectroheliograph is an instrument used in astronomy which captures a photographic image of the Sun at a single wavelength of light, a monochromatic image. The wavelength is usually chosen to coincide with a spectral wavelength of one of the ch ...

simultaneously with

George Hale George Ellery Hale (June 29, 1868 – February 21, 1938) was an American solar astronomer, best known for his discovery of magnetic fields in sunspots, and as the leader or key figure in the planning or construction of several world-lea ...

. In 1898, he joined Janssen at Meudon, increasing the scientific staff by 100%. On Janssen's death in 1907, Deslandres became director and embarked on a programme of expansion. Deslandres was the President of the Société Astronomique de France (SAF), the French astronomical society, from 1907-1909.de la Société astronomique de France'', 1911, vol. 25, pp. 581-586
/ref> At the outbreak of

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

in 1914, though already in his 60s, he returned to active service in the engineers as a

major Major (commandant in certain jurisdictions) is a military rank of commissioned officer status, with corresponding ranks existing in many military forces throughout the world. When used unhyphenated and in conjunction with no other indicators ...

and later

lieutenant colonel Lieutenant colonel ( , ) is a rank of commissioned officers in the armies, most marine forces and some air forces of the world, above a major and below a colonel. Several police forces in the United States use the rank of lieutenant colone ...

. In 1918, following the

armistice An armistice is a formal agreement of warring parties to stop fighting. It is not necessarily the end of a war, as it may constitute only a cessation of hostilities while an attempt is made to negotiate a lasting peace. It is derived from the La ...

, he resumed his office at Meudon until 1926 when its administration merged with that of the Paris Observatory, Mouchez assuming the role of director of both institutions until his retirement in 1929. He remained active in research right up until his death. Fellow astronomer Raymond Michard observed that ''In his bearing, his character and his style of life Deslandres always remained more akin to the soldier (and the officer) than to the scholar.'' Delegates to the Fourth Conference International Union for Cooperation in Solar Research at Mount Wilson Observatory

Delegates to the Fourth Conference International Union for Cooperation in Solar Research at Mount Wilson Observatory

Honours

Awards *

Gold Medal of the Royal Astronomical Society The Gold Medal of the Royal Astronomical Society is the highest award given by the Royal Astronomical Society (RAS). The RAS Council have "complete freedom as to the grounds on which it is awarded" and it can be awarded for any reason. Past awar ...

, (1913) *

Henry Draper Medal The Henry Draper Medal is awarded every 4 years by the United States National Academy of Sciences "for investigations in astrophysics, astronomical physics". Named after Henry Draper, the medal is awarded with a gift of USD $15,000. The medal was ...

of the

National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the Nati ...

, (1913) *

Prix Jules Janssen The Prix Jules Janssen is the highest award of the Société astronomique de France (SAF), the French astronomical society. This annual prize is given to a professional French astronomer or to an astronomer of another nationality in recognition ...

, the highest award of the

Société astronomique de France The Société astronomique de France (SAF; ), the French astronomical society, is a non-profit association in the public interest organized under French law (Association loi de 1901). Founded by astronomer Camille Flammarion in 1887, its purpose ...

, the French astronomical society, (1920) *

Bruce Medal The Catherine Wolfe Bruce Gold Medal is awarded every year by the Astronomical Society of the Pacific for outstanding lifetime contributions to astronomy. It is named after Catherine Wolfe Bruce, an American patroness of astronomy, and was firs ...

of the Astronomical Society of the Pacific, (1921) *

Fellow of the Royal Society Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the judges of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural science, natural knowledge, incl ...

Named after him *The crater Deslandres on the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

*Deslandres Prize of the

French Academy of Sciences The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV of France, Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific me ...

Asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

11763 Deslandres

References

External links

Biography by Joseph S. Tenn

Obituaries

(one paragraph)

(one paragraph) {{DEFAULTSORT:Deslandres, Henri 1853 births 1948 deaths 20th-century French astronomers French astrophysicists Recipients of the Bruce Medal Recipients of the Gold Medal of the Royal Astronomical Society Members of the French Academy of Sciences Foreign associates of the National Academy of Sciences Foreign Members of the Royal Society Corresponding members of the Saint Petersburg Academy of Sciences Corresponding Members of the Russian Academy of Sciences (1917–1925) Corresponding Members of the USSR Academy of Sciences University of Paris alumni 19th-century French astronomers 19th-century French physicists 20th-century French physicists Members of the Royal Society of Sciences in Uppsala École Polytechnique alumni