Roger Victor Émile Cayrel (4 December 1925 – 11 January 2021) was a French
astronomer
An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, natural satellite, moons, comets and galaxy, g ...
. His main interests were
stellar atmosphere
The stellar atmosphere is the outer region of the volume of a star, lying above the stellar core, radiation zone and convection zone.
Overview
The stellar atmosphere is divided into several regions of distinct character:
* The photosphere, which ...
s, galactic chemical evolution and
metal-poor
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...
stars.
Biography
Born in
Bordeaux
Bordeaux ( , ; Gascon oc, Bordèu ; eu, Bordele; it, Bordò; es, Burdeos) is a port city on the river Garonne in the Gironde department, Southwestern France. It is the capital of the Nouvelle-Aquitaine region, as well as the prefectur ...
, France, he attended the ''Lycée Michel-Montaigne'' in Bordeaux and studied physics at the
École normale supérieure
École may refer to:
* an elementary school in the French educational stages normally followed by secondary education establishments (collège and lycée)
* École (river), a tributary of the Seine flowing in région Île-de-France
* École, Savoi ...
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
The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...
commission on stellar atmospheres (1973–1976) and head of the
Bureau des Longitudes
Bureau ( ) may refer to:
Agencies and organizations
*Government agency
*Public administration
* News bureau, an office for gathering or distributing news, generally for a given geographical location
* Bureau (European Parliament), the administrat ...
(1995–1996).
Cayrel was a corresponding member of the
Académie des Sciences
The French Academy of Sciences (French: ''Académie des 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. It was at the ...
from 1988 to 2021. He was awarded the
Prix Jules Janssen
The Prix Jules Janssen is the highest award of the Société astronomique de France (SAF), the French astronomical society.
This annual prize is given to a professional French astronomer or to an astronomer of another nationality in recognition ...
of the
Société astronomique de France
The Société astronomique de France (SAF; ), the French astronomical society, is a non-profit association in the public interest organized under French law (Association loi de 1901). Founded by astronomer Camille Flammarion in 1887, its purpose ...
(Astronomical Society of France), in 2001.
Cayrel and his colleagues discovered
thorium
Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high me ...
and
uranium
Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
in the ultra-metal-poor halo star BPS CS31082-0001, which was named
Cayrel's Star
BPS CS31082-0001, named Cayrel's Star , is an old Population II star located in a distance of 2.1 kpc in the galactic halo. It belongs to the class of ultra-metal-poor stars (metallicity Fe/Hydrogen.html"_;"title="Iron.html"_;"title="/ ...
to honour him. From the thorium and uranium content, an age of 12.5 Billion years could be calculated.
Since 1954, he was married to the Italian astronomer
Giusa de Strobel.
References
Sources
* Cayrel, R.; Hill, V.; Beers, T. C.; Barbuy, B.; Spite, M.; Spite, F.; Plez, B.; Andersen, J.; Bonifacio, P.; François, P.; Molaro, P.; Nordström, B.;
Primas, F., Measurement of stellar age from uranium decay, Nature, Volume 409, Issue 6821, pp. 691–692 (2001)
* Jugaku, Jun. "The Publications And Citations Of Giusa And Roger Cayrel", ''Astrophysics and Space Science'' 265, 3(1999).
1925 births
2021 deaths
20th-century French astronomers
Members of the French Academy of Sciences
École Normale Supérieure alumni
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