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Cayrel's Star
BPS CS31082-0001, named Cayrel's Star,〔(Space Math @ NASA )〕 is an old Population II star located in a distance of 4 kpc in the Galactic Halo. It belongs to the class of ultra-metal-poor stars (metallicity (HREF="http://www.kotoba.ne.jp/word/11/Iron" TITLE="Iron">Fe/H ) = -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 and analyzed by Roger Cayrel and collaborators. They used the Very Large Telescope (VLT) at the European Southern Observatory in Paranal, Chile for high-resolution optical spectroscopy to determine elemental abundances. The thorium-232 to uranium-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 enriched stars (as CS22892-052, BD +17° 3248, HE 1523-0901) CS31082-001 has higher abundances of the actinides (Th, U), but a surprisingly low Pb abundance.
==See also==
;Ultra low metallicity / ultra metal poor stars
* HE0107-5240
* HE 1327-2326
* SDSS J102915+172927
* SMSS J031300.36-670839.3
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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