Background
Henri Deslandres was born on July 24, 1853 in Paris, France. He was born into a family typical of the mid-nineteenth-century French bourgeoisie.
École Polytechnique.
Académie des Sciences.
The Royal Society.
The Royal Astronomical Society.
Accademia dei Lincei.
The National Academy of Sciences.
A photo of Deslandres.
Deslandres (right) and Weisler (left) at work.
D'Azambuja (left) and Deslandres (right) in 1903.
The crater Deslandres.
The Janssen Medal.
The Gold Medal of the Royal Astronomical Society.
The Henry Draper Medal.
The Prix Jules Janssen.
The Bruce Medal.
Sorbonne University.
Astronomer physicist scientist
Henri Deslandres was born on July 24, 1853 in Paris, France. He was born into a family typical of the mid-nineteenth-century French bourgeoisie.
Deslandres graduated from the École Polytechnique in 1874. Later at the Sorbonne, he received his doctorate in 1888. In his thesis Deslandres studied the spectra of molecules such as nitrogen, cyanogen, CH, and water and recognized two simple laws in the disconcerting complexity of the numerous bands, each of which is made up of many tens of lines. These laws bear his name, and were at first useful in the empirical study and classification of molecular spectra; later, with the elaboration of quantum mechanics, it became easy to explain them in terms of the structure of molecules.
In 1874 Deslandres entered the army, in which he served until 1881, when a strong interest in physical sciences led him to resign his military position. He worked first in the physical laboratories of the École Polytechnique and the Sorbonne, devoting himself to ultraviolet spectroscopy under the guidance of M. A. Cornu.
After this splendid success in laboratory spectroscopy, Deslandres turned in 1889 to astrophysics without losing interest in molecules, as is shown by his fine observations of the Zeeman effect on molecular fines. In numerous publications of his late years he sought a unified theoretical interpretation of molecular spectra; he paid little attention to such modernist developments as quantum mechanics.
In 1889 Deslandres joined the staff of the Paris observatory, then headed by Admiral Ernest Mouchez, who sought to develop astrophysics in the institution long dedicated to celestial mechanics under Le Verrier.
At the Paris observatory Deslandres attached a spectrograph to the recently built 120-cm. mirror telescope and began observing the spectra of stars and planets, devoting himself to the measurement of fine-of-sight velocities through the Doppler-Fizeau effect, the most essential tool of the astronomer in studying the motions and dynamics of celestial bodies. He continued the same type of observations in Meudon with a spectrograph attached to a large refractor with an 83-cm. aperture. Among his most valuable results were the law of rotation of Saturn’s ring (1895), which was shown to rotate as a system of independent particles and not as a solid body, and the proof that Uranus (like its known satellites) rotates in the direction opposite to all other planets, a fact of significance to cosmogony.
In 1897 he joined Jules Janssen at his astrophysical observatory in Meudon and became its director in 1908, following Janssen’s death. In 1926 the Paris and Meudon observatories were united under his management. Deslandres retired in 1929 but pursued an active scientific life almost until his death at the age of ninety-four.
During his long and successful career Deslandres was elected to essentially all the scientific societies of significance, including the Académie des Sciences (1902; president, 1920), the Royal Society, the Royal Astronomical Society, the Accademia dei Lincei, and the National Academy of Sciences of the United States.
In his bearing, his character, and his style of life Deslandres always remained more akin to the soldier than to the scholar. These consequences of his education also appeared in his scientific work - he was more successful in the experimental and technical aspects of physics and astrophysics than in creating new theories.