BD + 17 ° 3248

BD + 17 ° 3248 is an old population-II - Star in the Halo of the Milky Way . It belongs to the rare class of ultra-metal-poor stars ( metallicity [Fe / H] = - 2.1), and in turn to the rare subclass with an abundance of r-process elements.

Detailed high-resolution spectroscopic investigations have been carried out on three large devices since 2000 (with Chris Sneden of the University of Texas at Austin as the leading observer):

the Hubble Space Telescope (NASA / ESA Hubble Space Telescope),
the Keck I Telescope in Hawaii and
the HJ Smith Telescope at the University of Texas' McDonald Observatory .

The interaction of these telescopes made it possible to determine the abundance of elements in this star over a wide range: from germanium (Z = 32) to uranium (Z = 92). With the Hubble Telescope stationed in space, it was also possible to record spectra in the ultraviolet , rays that are absorbed by the earth's atmosphere. In this way, the heavy metals osmium , platinum and, for the first time, gold in an ultra-low-metal star could be determined. The detection of the radioactive metals thorium and uranium (only the second detection in such a star after CS31082-001 ) allows a reliable age determination by comparison with one another and with stable elements.

All frequencies for elements heavier than barium (Z = 56) show the pattern of the elements formed by the r-process in the solar system. By comparing the frequencies of a stable element such as europium (Z = 63) and the radioactive elements thorium (Z = 90) and uranium (Z = 92) observed in the star with the calculated frequencies of these elements in a type II supernova explosion (as reported by the groups of Karl-Ludwig Kratz in Mainz and Friedrich-Karl Thielemann in Basel) results in an age of about 13.8 billion years (with an uncertainty of 4 billion years) for this star, which is only a little later than the Big Bang came into being. Corresponding ages were determined for other ultra-metal-poor stars like CS22892-052 or CS31082-001 . The agreement of the element abundances of the elements formed in the r-process heavier than Ba in the very old stars and in the solar system means that this nucleosynthesis process has been based on the same principle since the beginning.

literature

TC Beers, GW Preston, SA Shectman: A search for stars of very low metal abundance. I. In: Astron. J. , 90, 1985, pp. 2089-2102.
TC Beers, GW Preston, SA Shectman: A search for stars of very low metal abundance. II. In: Astron. J. , 103, 1992, pp. 1987-2034.
Karl-Ludwig Kratz , Jean-Philippe Bitouzet, Friedrich-Karl Thielemann, Peter Moeller, Bernd Pfeiffer: Isotopic r-process abundances and nuclear structure far from stability - Implications for the r-process mechanism. In: Astrophysical Journal , 403 (1), 1993, pp. 216-238.
JJ Cowan, C. Sneden, S. Burles, II Ivans, TC Beers, JW Truran, JE Lawler, F. Primas, GM Fuller, B. Pfeiffer, K.-L. Kratz : The Chemical Composition and Age of the Metal-Poor Halo Star BD + 17 ° 3248. In: Ap. J. , 572, 2002, pp. 861-879.

Web links

R-Process Cosmo-Chronometers ( Memento from April 15, 2012 in the Internet Archive )
The Chemical Composition and Age of the Metal-Poor Halo Star BD + 17 ° 3248 . arxiv : astro-ph / 0202429
Gold discovered on a distant star. On: Wissenschaft.de from January 12, 2002

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g BD +17 3248. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed October 27, 2019 .

[Simbad-1] ↑ ^a ^b ^c ^d ^e ^f ^g BD +17 3248. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed October 27, 2019 .