BD+173248 (star)
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| Observation data Equinox J2000 |
|
|---|---|
| Constellation | Hercules |
| Right ascension | 17h 28m 14s |
| Declination | +17° 30' 36" |
| Apparent magnitude (V) | 9.4 |
BD +17° 3248 is an old Population II star located in a distance of 272 pc in the Galactic Halo. It belongs to the class of ultra-metal-poor stars (Metallicity Fe/H=–3.1) , especially the very rare subclass of neutron-capture (r-process) enhanced stars.
Since about 2000, this star had been analyzed with 3 telescopes: a) the Hubble Space Telescope, b) the Keck I telescope and c) the Harlan J. Smith Telescope at the McDonald Observatory of the University of Texas. Elemental abundances in the range from Germanium (Z=32) up to Uranium (Z=92) could be determined. With the Hubble Space Telescope also the ultraviolet part of the stellar spectra could be observed. This allowed to measure Platinum, Osmium and for the first time outside of the Solar System Gold. From Barium (Z=56) on, all elements show the pattern of the r-process contribution to the abundances of the elements in the Solar system. Comparing the observed abundances for a stable element as Europium (Z=63) and the radioactive elements Thorium (Z=90) and Uranium (Z=92) to calculated abundances of an r-process in a type II supernova explosion (as from the universities at Mainz and Basel groups of Karl-Ludwig Kratz and Friedrich-Karl Thielemann) allowed to determine the age of this star to about 13.8 billion years (with an uncertainty of 4 billion years). A similar age had been derived for another ultra-metal-poor star (CS31082-001 from Thorium to Uranium ratios. These stars were already born several hundred million years after the Big Bang.
[edit] References
- BEERS T.C., PRESTON G.W., SHECTMAN S.A., A search for stars of very low metal abundance. I., Astron. J., 90, 2089-2102 (1985)
- BEERS T.C., PRESTON G.W., SHECTMAN S.A., A search for stars of very low metal abundance. II., Astron. J., 103, 1987-2034 (1992)
- Kratz, Karl-Ludwig; Bitouzet, Jean-Philippe; Thielemann, Friedrich-Karl; Moeller, Peter; Pfeiffer, Bernd, Isotopic r-process abundances and nuclear structure far from stability - Implications for the r-process mechanism, Astrophysical Journal, vol. 403, no. 1, p. 216-238 (1993)
- Sneden, Christopher; McWilliam, Andrew; Preston, George W.; Cowan, John J.; Burris, Debra L.; Armosky, Bradley J., The Ultra--Metal-poor, Neutron-Capture--rich Giant Star CS 22892-052, Astrophysical Journal v.467, p.819 (1996)
- J.J. Cowan, C. Sneden, S. Burles, I.I. Ivans, T.C. Beers, J.W. Truran, J.E. Lawler, F. Primas, G.M. Fuller, B. Pfeiffer, and K.-L. Kratz: The Chemical Composition and Age of the Metal-Poor Halo Star BD +17°3248, Ap.J. 572 (2002) 861 - 879
