Bernard Lyot (1897–1952)

Bernard Ferdinand Lyot was born in Paris on 27 February 1897. After obtaining a degree in engineering in 1918, he worked for over ten years as a demonstrator in Physics at the Ecole Polytechnique in Paris. In 1930 he took on an Astronomer position at the Observatoire de Meudon, where he had held an Assistant Astronomer appointment since 1920, and where he became Chief Astronomer in 1943. In 1939 he was elected to the Académie des Sciences and was awarded the Gold Medal of the Royal Astronomical Society. More honors followed with the Bruce Medal in 1947, and the Draper Medal of the US National Academy of Sciences in 1952.

Bernard Lyot image
Portrait of Bernard Lyot (1897–1952).
Credit: The Bruce Medalists.

Lyot's first astronomical researches aimed at measuring the polarization of sunlight reflected from moons and planets, in order to infer something of their surface's composition. Not only was Lyot quite successful at this, but it is while working on Mercury that he began to contemplate ways to eliminate the glare of the solar disk while carrying out observations very close to the sun's limbs. This led to his design of the "coronagraph", with which he secured on 12 July 1931 at the Observatoire du Pic-du Midi, the first photograph of the corona ever taken outside of an eclipse. He also went on to obtain the first cinematographic movie of solar prominences. Lyot's coronagraph also allowed extensive spectroscopic studies of the faint coronal lines. Lyot himself noted the surprising width of these lines, a crucial clue toward the realization that the coronal gas is very much hotter then hitherto believed. Lyot also designed the polarization filters now bearing his name, which allow much narrower bandwidths than with conventional filters.

A modest and generous man, Lyot never failed to provide help and support to other scientists requesting his help in instrumental matters. He died on 2 April 1952 near Cairo, Egypt, following a heart attack suffered while on his way back from an observing expedition at the total solar eclipse of 25 February 1952 near Khartoum, Sudan.

Bibliography:
D'Azambuja, L. 1952, L'oeuvre de Bernard Lyot, L'Astronomie, 66, 267-277.
Porter, R. (ed.) 1994, The Biographical Dictionary of Scientists, Oxford University Press.