Henri-Alexandre Deslandres
Encyclopedia
Henri Alexandre Deslandres (July 24, 1853 – January 15, 1948) was a French
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...

 astronomer
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...

, director of the Meudon and Paris Observatories
Paris Observatory
The Paris Observatory is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world...

.

Deslandres' undergraduate years at the École Polytechnique
École Polytechnique
The École Polytechnique is a state-run institution of higher education and research in Palaiseau, Essonne, France, near Paris. Polytechnique is renowned for its four year undergraduate/graduate Master's program...

 were played out against the aftermath of the Franco-Prussian War
Franco-Prussian War
The Franco-Prussian War or Franco-German War, often referred to in France as the 1870 War was a conflict between the Second French Empire and the Kingdom of Prussia. Prussia was aided by the North German Confederation, of which it was a member, and the South German states of Baden, Württemberg and...

 and the chaos of the Paris Commune
Paris Commune
The Paris Commune was a government that briefly ruled Paris from March 18 to May 28, 1871. It existed before the split between anarchists and Marxists had taken place, and it is hailed by both groups as the first assumption of power by the working class during the Industrial Revolution...

 so, on graduation in 1874, he responded to the continuing military tension with the emerging Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 by embarking on a military career. Rising to the rank of captain in the engineers, he became increasingly interested in physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

 and, in 1881, resigned his commission to join Alfred Cornu's laboratory at the École Polytechnique, working on spectroscopy
Spectroscopy
Spectroscopy is the study of the interaction between matter and radiated energy. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, e.g., by a prism. Later the concept was expanded greatly to comprise any interaction with radiative...

. He continued his spectroscopic work at the Sorbonne
University of Paris
The University of Paris was a university located in Paris, France and one of the earliest to be established in Europe. It was founded in the mid 12th century, and officially recognized as a university probably between 1160 and 1250...

, earning his doctorate in 1888 and finding numerical patterns in spectral line
Spectral line
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from a deficiency or excess of photons in a narrow frequency range, compared with the nearby frequencies.- Types of line spectra :...

s that paralleled the work of Johann Balmer and were to catalyse the development of quantum mechanics
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...

 in the 20th century.

In 1868, Pierre Janssen's solar observations had led him to report to the Académie des Sciences that It is no longer geometry and mechanics which dominate [in astronomy] but physics and chemistry. Such advice was sternly rejected by director of the Paris Observatory
Paris Observatory
The Paris Observatory is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world...

 Urbain Le Verrier and the French government awarded Janssen a grant to establish an astrophysical observatory at Meudon
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.-Geography:...

 on the outskirts of Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...

 with Janssen as the sole astronomer. In 1889, Le Verrier was succeeded by Amédée Mouchez
Amédée Mouchez
Amédée Ernest Barthélemy Mouchez was a French naval officer who became director of the Paris Observatory and launched the ill-fated Carte du Ciel project in 1887.-Life:...

 who set to work to bring astrophysics into the mainstream by hiring Deslandres. Deslandres developed the spectroheliograph
Spectroheliograph
The spectroheliograph is an instrument used in astronomy. It captures a photographic image of the Sun at a single wavelength of light, a monochromatic image...

 simultaneously with George Hale.

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. At the outbreak of World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 in 1914, though already in his 60s, he returned to active service in the engineers as a major
Major
Major is a rank of commissioned officer, with corresponding ranks existing in almost every military in the world.When used unhyphenated, in conjunction with no other indicator of rank, the term refers to the rank just senior to that of an Army captain and just below the rank of lieutenant colonel. ...

 and later lieutenant colonel
Lieutenant colonel
Lieutenant colonel is a rank of commissioned officer in the armies and most marine forces and some air forces of the world, typically ranking above a major and below a colonel. The rank of lieutenant colonel is often shortened to simply "colonel" in conversation and in unofficial correspondence...

. In 1918, following the armistice
Armistice
An armistice is a situation in a war where the warring parties agree to stop fighting. It is not necessarily the end of a war, but may be just a cessation of hostilities while an attempt is made to negotiate a lasting peace...

, 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.

Honours

Awards
  • Gold Medal of the Royal Astronomical Society
    Gold Medal of the Royal Astronomical Society
    -History:In the early years, more than one medal was often awarded in a year, but by 1833 only one medal was being awarded per year. This caused a problem when Neptune was discovered in 1846, because many felt an award should jointly be made to John Couch Adams and Urbain Le Verrier...

    , (1913)
  • Henry Draper Medal
    Henry Draper Medal
    The Henry Draper Medal is awarded by the United States National Academy of Sciences "for investigations in astronomical physics". Named after Henry Draper, the medal is awarded with a gift of USD $15,000...

     of the National Academy of Sciences
    United States National Academy of Sciences
    The National Academy of Sciences is a corporation in the United States whose members serve pro bono as "advisers to the nation on science, engineering, and medicine." As a national academy, new members of the organization are elected annually by current members, based on their distinguished and...

    , (1913)
  • Bruce Medal
    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 first awarded in 1898...

     of the Astronomical Society of the Pacific
    Astronomical Society of the Pacific
    The Astronomical Society of the Pacific is a scientific and educational organization, founded in San Francisco on February 7, 1889. Its name derives from its origins on the Pacific Coast, but today it has members all over the country and the world...

    , (1921)

Named after him
  • The crater Deslandres
    Deslandres (crater)
    Deslandres is the heavily worn and distorted remains of a lunar impact crater. It is located to the southeast of the Mare Nubium, in the rugged southern highlands of the Moon. In dimension it is the second-largest crater formation on the visible Moon, being beaten only by the 303-kilometer-diameter...

     on the Moon
    Moon
    The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

  • Deslandres Prize of the French Academy of Sciences
    French Academy of Sciences
    The French Academy of 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...

  • Asteroid
    Asteroid
    Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...

     11763 Deslandres
    11763 Deslandres
    11763 Deslandres is a main belt asteroid with an orbital period of 1786.4180423 days . The asteroid was discovered on September 24, 1960.-References:...


External links


Obituaries

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