Roger Victor Émile Cayrel (4 December 1925 – 11 January 2021) was a French astronomer.
His main interests were stellar atmospheres, galactic chemical evolution and metal-poor stars.
[1] Born in Bordeaux, France, he attended the Lycée Michel-Montaigne in Bordeaux and studied physics at the École normale supérieure and the Faculté des sciences de Paris.
Beside his scientific work, he had a number of high-ranking posts in the management of science: director of the Canada-France-Hawaii Telescope (CFHT, 1974–1980), president of the IAU commission on stellar atmospheres (1973–1976) and head of the Bureau des Longitudes (1995–1996).
From the thorium and uranium content, an age of 12.5 Billion years could be calculated.