BPS CS31082-0001, named Cayrel's Star ,
/ref> is an old

Population II During 1944, Walter Baade categorized groups of stars within the Milky Way into stellar populations. In the abstract of the article by Baade, he recognizes that Jan Oort originally conceived this type of classification in 1926: Baade noticed th ...

star A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...

located in a distance of 2.1 kpc in the

galactic halo A galactic halo is an extended, roughly spherical component of a galaxy which extends beyond the main, visible component. Several distinct components of galaxies comprise the halo: * the stellar halo * the galactic corona (hot gas, i.e. a plas ...

. It belongs to the class of ultra-

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 ...

stars (

metallicity 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 ...

Fe/Hydrogen">H">Iron">Fe<_a>_Hydrogen.html" ;"title="Iron.html" ;"title="/nowiki>Iron">Fe/Hydrogen">H/nowiki> = -2.9), specifically the very rare subclass of neutron-capture enhanced stars. It was discovered by Tim C. Beers and collaborators with the Curtis Schmidt telescope at the Cerro Tololo Inter-American Observatory in

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...

and analyzed by Roger Cayrel and collaborators. They used the Very Large Telescope ( Very Large Telescope, VLT) at the

European Southern Observatory The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental organization, intergovernmental research organisation made up of 16 mem ...

Paranal Cerro Paranal is a mountain in the Atacama Desert of northern Chile and is the home of the Paranal Observatory. Prior to the construction of the observatory, the summit was a horizontal control point with an elevation of ; now it is above sea ...

for high-resolution optical

spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter ...

to determine

elemental abundances An elemental is a mythic being that is described in occult and alchemical works from around the time of the European Renaissance, and particularly elaborated in the 16th century works of Paracelsus. According to Paracelsus and his subsequent fol ...

. The

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 ...

-232 to

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 weakly ...

-238 ratio was used to determine the age. It is estimated to be about 12.5 billion years old, making it one of the oldest known. Compared to other ultra-metal-poor,

r-process In nuclear astrophysics, the rapid neutron-capture process, also known as the ''r''-process, is a set of nuclear reactions that is responsible for the creation of approximately half of the atomic nuclei heavier than iron, the "heavy elements", ...

enriched stars (as CS22892-052,

BD +17° 3248 BD, Bd or bd may refer to: In arts and entertainment * B. D. (Doonesbury), a major character in the ''Doonesbury'' comic strip * '' Bande dessinée'' (or "bédé"), a French term for comics * Bass drum, in sheet music notation * Brahe Djäk ...

HE 1523-0901 HE 1523-0901 is the designation given to a red giant star in the Milky Way galaxy approximately 7500 light years from Earth. It is thought to be a second generation, Population II, or metal-poor, star ( e/Hnbsp;= −2.95). The star w ...

) CS31082-001 has higher abundances of the

actinide The actinide () or actinoid () series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium. The inf ...

s ( Th, U), but a surprisingly low Pb abundance.

References

Sources

* Beers, T. C., G. W. Preston and S. A. Shectman, ''A search for stars of very low metal abundance. I.'', Astron. J., 90, 2089–2102 (1985) * Beers, T. C., G. W. Preston and S. A. Shectman, ''A search for stars of very low metal abundance. II.'', Astron. J., 103, 1987–2034 (1992) * Cayrel, R., et al. ''Measurement of stellar age from uranium decay'', Nature, Volume 409, Issue 6821, pp. 691–692 (2001) * Schatz, H., al. ''Thorium and Uranium Chronometres applied to CS 31082-001'', Astrophysical Journal, 579 (2002) 628–638

External links

*
arXiv: Measurement of stellar age from uranium decay
R. §Cayrel et al.

{{DEFAULTSORT:Cayrel's Star Population II stars Cetus (constellation)

See also

References

Sources

External links