The Lake County Astronomical Society

Astronomy Bio...Bernard Lyot

Jay Bitterman

Bernard Lyot was born in France on February 27, 1897, to Dr. Constant Lyot, a Paris surgeon and his wife Alice. He went to elementary school at the Lycee Janson de Sailly. He then went to the École Supérieur d'Électricité to become an electrical engineer and graduated in 1917; in 1918 he received a diploma in engineering. While at school, in 1914, he became interested in physics and astronomy and started to observe the sky using a 4-inch telescope. He subsequently acquired a 6-inch telescope that he set up near Tours in a dome that he constructed. For eleven years after graduation from the École Supérieur, he was a demonstrator in the physics department at the École Polytechnique. There he worked under the celebrated physicists Alfred Pérot and Charles Fabry while taking courses in mathematics, physics and chemistry at the University of Paris.

In 1920 he became Assistant Astronomer at the Meudon Observatory. Throughout the 1920s he devoted most of his research to the study of polarized light that was reflected to Earth from the Moon and other planets. In 1924 he reported that a layer of volcanic ash probably covered the Moon and that dust storms were a common feature of the Martian surface. He also claimed to have discovered water vapor on the surface of Venus. (It was later demonstrated that the small amounts of water vapor that actually were there could not have been seen using Lyot's instruments.)

In 1930 Lyot attained the title of Joint Astronomer at the Observatory, and started to work full time. He earned an international reputation for his advances in the study of polarized and monochromatic light. Besides designing a polariscope of extremely improved sensitivity, Lyot made numerous observations of the surfaces and atmospheric conditions on other planets.

For centuries, astronomers trying to study the solar corona were confined to the rare and brief opportunity during the total eclipse of the Sun. The main difficulty in using optical instruments previously involved the "scattering" of light by even the slightest particle of dust or the minutest fault in the object lens which caused the corona (that has only one millionth of the brilliance of the solar disc) to became totally obscured. In 1930, in order to overcome this problem, he ground three nearly flawless 8-cm object lenses having a 2-m focal length. By incorporating these lenses with diaphragms within his coronagraph he cut off light from the solar disk. To test the instrument he sought the clear air of the Pic du Midi Observatory in the Pyrenees at an altitude of 2,870-m. Finally, for the first time in astronomical history he was able to observe the corona in broad daylight.

Throughout the 1930s Lyot made improvements on the coronagraph by increasing the diameter and focal length of the object lens and he added a sophisticated monochromatic filter. The filter allowed him to intensify the most important wavelengths of the coronal light and increase his observing time. His coronagraph also allowed the observation of constant changes of the corona. In 1935 Lyot demonstrated for the first time that the corona could be photographed and he observed the rotation of the corona in synchrony with the Sun.

In 1938 at the International Astronomical Union at Stockholm he showed his motion picture of the solar atmosphere in action. His later work included the fabrication of the photoelectric polarimeter that made it easier to conduct in-depth research on the solar corona.

In 1939 he was elected to the French Academy of Sciences and also was awarded the Gold Medal of the Royal Astronomical Society in London.

All of these developments were made from 1920 to 1952 while he worked at the Meudon-Observatory, which had become part of the Paris Observatory in 1926. In 1943 he became Chief Astronomer at the Meudon Observatory. He published several books that outlined his discoveries and innovations.

In 1947 Lyot received the Bruce Medal and was the fourth Frenchman to be so honored. The others are J. H. Poincare in 1911; H. A. Deslandres in 1921; and B.Baillaud in 1923. He is the third astronomer named for work primarily on the sun, others being G. E. Hale and Lyot's fellow countryman, Deslandres

In 1952 Lyot traveled to the Sudan to observe a total eclipse of the Sun. While there he suffered a heart attack on the train journey home and died near Cairo, Egypt, on April 2, 1952.