BPS CS22892-0052 (Sneden's Star) is an old population II

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

located at a distance of 4.7 kpc in the galactic halo. It belongs to a class of ultra- metal-poor stars (

Metallicity In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...

e/H-3.1), specifically the very rare subclass of neutron-capture (

r-process In nuclear astrophysics, the rapid neutron-capture process, also known as the ''r''-process, is a set of nuclear reactions that is responsible for the creation of approximately half of the atomic nuclei heavier than iron, the "heavy elements", ...

) 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 Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

. Extended high-resolution spectroscopic observations since around 1995 (with Chris Sneden from the

University of Texas at Austin The University of Texas at Austin (UT Austin, UT, or Texas) is a public research university in Austin, Texas. It was founded in 1883 and is the oldest institution in the University of Texas System. With 40,916 undergraduate students, 11,075 ...

as the leading observer) allowed observers to determine the abundances of 53

chemical element A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...

s in this star, as of December 2005 only second in number to the Sun. From

barium Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Th ...

(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 A stable is a building in which livestock, especially horses, are kept. It most commonly means a building that is divided into separate Stall (livestock), stalls for individual animals and livestock. There are many different types of stables ...

such as

europium Europium is a chemical element with the symbol Eu and atomic number 63. Europium is the most reactive lanthanide by far, having to be stored under an inert fluid to protect it from atmospheric oxygen or moisture. Europium is also the softest lanth ...

(Z=63) and the radioactive element

thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high me ...

(Z=90) to calculated abundances of an r-process in a type II

supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...

explosion (as from the universities at

Mainz Mainz () is the capital and largest city of Rhineland-Palatinate, Germany. Mainz is on the left bank of the Rhine, opposite to the place that the Main (river), Main joins the Rhine. Downstream of the confluence, the Rhine flows to the north-we ...

and

Basel , french: link=no, Bâlois(e), it, Basilese , neighboring_municipalities= Allschwil (BL), Hégenheim (FR-68), Binningen (BL), Birsfelden (BL), Bottmingen (BL), Huningue (FR-68), Münchenstein (BL), Muttenz (BL), Reinach (BL), Riehen (BS ...

groups of

Karl-Ludwig Kratz Karl-Ludwig Kratz (born April 23, 1941, in Jena, Thuringia) is a German nuclear chemist and astrophysicist. He is professor for nuclear chemistry at the Johannes Gutenberg University of Mainz and adjunct professor of physics at the University of ...

and

Friedrich-Karl Thielemann Friedrich-Karl "Friedel“ Thielemann (born 17 April 1951 in Mülheim an der Ruhr) is a German-Swiss theoretical astrophysicist. Thielemann studied at the TH Darmstadt, where he in 1976 he acquired his Diplom. In 1980 he earned his PhD under Wo ...

) have allowed observers to determine the age of this star to be about 13 billion years. Similar ages have been derived for other ultra-metal-poor stars ( CS31082-001,

BD+17°3248 BD+17°3248 is an old Population II star located at a distance of roughly in the Galactic Halo. It belongs to the class of ultra-metal-poor stars, especially the very rare subclass of neutron-capture (r-process) enhanced stars. Since abo ...

and

HE 1523-0901 HE 1523-0901 is the designation given to a red giant star in the Milky Way galaxy approximately 7500 light years from Earth. It is thought to be a second generation, Population II, or metal-poor, star ( e/Hnbsp;= −2.95). The star ...

) from thorium-to-

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

ratios.

References

Sources

* 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) * Cowan, John J.; Pfeiffer, B.; Kratz, K.-L.; Thielemann, F.-K.; Sneden, Christopher; Burles, Scott; Tytler, David; Beers, Timothy C., ''R-Process Abundances and Chronometers in Metal-poor Stars'' The Astrophysical Journal, Volume 521, Issue 1, pp. 194–205 (1999)

External links

R-Process Cosmo-Chronometers

Image Sneden's Star
{{DEFAULTSORT:Sneden's Star K-type bright giants Asymptotic-giant-branch stars Population II stars Aquarius (constellation)