THE ULTRA-METAL-POOR, NEUTRON-CAPTURE-RICH GIANT STAR CS-22892-052

The K giant star CS 22892-052 is ultra-metal-poor ([Fe/H] similar or e qual to -3.1), but it has the largest abundance enhancements of neutro n-capture elements yet discovered in any normal halo star. We have acq uired new high-resolution, high signal-to-noise ratio spectra of CS 22 892-052 and have determined a detailed abundance distribution of eleme nts with Z > 30, in order to facilitate precise comparison with neutro n-capture nucleosynthesis theories. Over 120 transitions throughout th e wavelength range 3700-6500 Angstrom have been employed to derive abu ndances for 20 of these elements. We have detected several elements (T b, Ho, Tm, Hf, and Os) never before seen in low-metallicity stars, and we have derived the abundance of Th from a clearly visible, mostly un blended, feature at 4019 Angstrom. The elements from 56 less than or e qual to Z less than or equal to 76 in CS 22892-052 are very well match ed by a scaled solar system r-process abundance distribution. Scaled s olar s-process or total abundances cannot be plausibly fitted to the o bserved data. The ratio of the Th abundance to that of any of these ot her elements is significantly subsolar, which suggests a much larger a ge for CS 22892-052 than 4.5 Gyr; a lower limit of 15.2 +/- 3.7 Gyr is inferred from a simple calculation.