Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003trgeo...1...17z&link_type=abstract
Treatise on Geochemistry, Volume 1. Editor: Andrew M. Davis. Executive Editors: Heinrich D. Holland and Karl K. Turekian. pp. 71
Astronomy and Astrophysics
Astronomy
21
Scientific paper
Traditionally, astronomers have studied the stars by using, with rare exception, electromagnetic radiation received by telescopes on and above the Earth. Since the mid-1980s, an additional observational window has been opened in the form of microscopic presolar grains found in primitive meteorites. These grains had apparently formed in stellar outflows of late-type stars and in the ejecta of stellar explosions and had survived the formation of the solar system. They can be located in and extracted from their parent meteorites and studied in detail in the laboratory. Their stellar origin is recognized by their isotopic compositions, which are completely different from those of the solar system and, for some elements, cover extremely wide ranges, leaving little doubt that the grains are ancient stardust.By the 1950s it had been conclusively established that the elements from carbon on up are produced by nuclear reactions in stars and the classic papers by Burbidge et al. (1957) and Cameron (1957) provided a theoretical framework for stellar nucleosynthesis. According to these authors, nuclear processes produce elements with very different isotopic compositions, depending on the specific stellar source. The newly produced elements are injected into the interstellar medium (ISM) by stellar winds or as supernova (SN) ejecta, enriching the galaxy in "metals" (all elements heavier than helium) and after a long galactic history the solar system is believed to have formed from a mix of this material. In fact, the original work by Burbidge et al. and Cameron was stimulated by the observation of regularities in the abundance of the nuclides in the solar system as obtained by the study of meteorites (Suess and Urey, 1956). Although providing only a grand average of many stellar sources, the solar system abundances of the elements and isotopes ( Anders and Grevesse, 1989; Grevesse et al., 1996; see Chapter 1.03; Lodders, 2003) remained an important test for nucleosynthesis theory (e.g., Timmes et al., 1995).In contrast, the study of stellar grains permits information to be obtained about individual stars, complementing astronomical observations of elemental and isotopic abundances in stars (e.g., Lambert, 1991), by extending measurements to elements that cannot be measured astronomically. In addition to nucleosynthesis and stellar evolution, presolar grains provide information about galactic chemical evolution, physical properties in stellar atmospheres, mixing of SN ejecta and conditions in the parent bodies of the meteorites in which the grains are found.This new field of astronomy has grown to an extent that not all aspects of presolar grains can be treated in detail in this chapter. The interested reader is therefore referred to some recent reviews (Anders and Zinner, 1993; Ott, 1993; Zinner, 1998a, b; Hoppe and Zinner, 2000; Nittler, 2003) and to the compilation of papers found in Bernatowicz and Zinner (1997). The latter not only contains several detailed review papers on presolar dust grains but also a series of chapters on stellar nucleosynthesis. Further information on nucleosynthesis can be obtained from the textbooks by Clayton (1983b) and Arnett (1996), and from reviews by Köppeler et al. (1989), Meyer (1994), and Wallerstein et al. (1997).
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