Nuclear abundances and evolution of the interstellar medium
Abstract
Observations of molecular and elemental abundances in the interstellar medium (ISM) are reviewed, with special attention given to isotope ratios. The derivation of molecular isotope abundances for the ISM is discussed, along with H and C fractionation. Millimeter- and centimeter-wave spectra of giant clouds are examined with respect to isotope abundances of C, O, N, Si, S, and D. Evidence for the current enrichment of the ISM by mass loss from evolved stars is considered, together with chemical abundance gradients in H II regions and planetary nebulae. Cosmic-ray observations pertaining to abundances in the ISM are summarized, with emphasis on available results for Ne, Mg, Si, Fe, and Ni. The observations reviewed are shown to support arguments in favor of: (1) the cosmological production of D and He-3; (2) the production of the CNO elements by hydrostatic hydrogen burning; (3) the nucleosynthesis of Ne, Mg, Si, S, Fe, and Ni as a result of He burning; (4) solar abundances of interstellar S, Fe, and Ni; and (5) a direct association between observed inhomogeneities in the ISM and mass loss from evolved stellar objects.
- Publication:
-
Annual Review of Astronomy and Astrophysics
- Pub Date:
- 1980
- DOI:
- 10.1146/annurev.aa.18.090180.002151
- Bibcode:
- 1980ARA&A..18..399W
- Keywords:
-
- Abundance;
- Interstellar Chemistry;
- Interstellar Matter;
- Cosmic Rays;
- Galactic Nuclei;
- H Ii Regions;
- Nitrogen Isotopes;
- Nuclear Fusion;
- Oxygen Isotopes;
- Planetary Nebulae;
- Silicon Isotopes;
- Spatial Distribution;
- Stellar Mass Ejection;
- Sulfur Isotopes;
- Astrophysics