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

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

located in a distance of 2.1 kpc in the galactic halo. It belongs to the class of ultra- metal-poor stars (

metallicity In astronomy, metallicity is the Abundance of the chemical elements, abundance of Chemical element, elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-Dark matter, dark) matt ...

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 western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

and analyzed by Roger Cayrel and collaborators. They used the Very Large Telescope 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 m ...

in Paranal,

for high-resolution optical

spectroscopy Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectro ...

to determine elemental abundances. The

thorium Thorium is a chemical element; it has symbol Th and atomic number 90. Thorium is a weakly radioactive light silver metal which tarnishes olive grey when it is exposed to air, forming thorium dioxide; it is moderately soft, malleable, and ha ...

-232 to

uranium Uranium is a chemical element; it has chemical symbol, 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. Ura ...

-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 nucleosynthesis, the creation of approximately half of the Atomic nucleus, atomic nuclei Heavy meta ...

enriched stars (as CS22892-052, BD +17° 3248, HE 1523-0901) CS31082-001 has higher abundances of the

actinide The actinide () or actinoid () series encompasses at least the 14 metallic chemical elements in the 5f series, with atomic numbers from 89 to 102, actinium through nobelium. Number 103, lawrencium, is also generally included despite being part ...

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 Durchmusterung objects

See also

References

Sources

External links