BPS CS31082-0001, named Cayrel's Star /keɪˈrɛlz/,[3] is an old Population II star located in a distance of 2.1 kpc[1] in the galactic halo.
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.
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.