Origin and evolution of the light nuclides

Abstract

After a short historical (and highly subjective) introduction to the field, I discuss our current understanding of the origin and evolution of the light nuclides D, He-3, He-4, Li-6, Li-7, Be-9, B-10 and B-11. Despite considerable observational and theoretical progress, important uncertainties still persist for each and every one of those nuclides. The present-day abundance of D in the local interstellar medium is currently uncertain, making it difficult to infer the recent chemical evolution of the solar neighborhood. To account for the observed quasi-constancy of He-3 abundance from the Big Bang to our days, the stellar production of that nuclide must be negligible; however, the scarce observations of its abundance in planetary nebulae seem to contradict this idea. The observed Be and B evolution as primaries suggests that the source composition of cosmic rays has remained quasi-constant since the early days of the Galaxy, a suggestion with far reaching implications for the origin of cosmic rays; however, the main idea proposed to account for that constancy, namely that superbubbles are at the source of cosmic rays, encounters some serious difficulties. The best explanation for the mismatch between primordial Li and the observed "Spite-plateau" in halo stars appears to be depletion of Li in stellar envelopes, by some yet poorly understood mechanism. But this explanation impacts on the level of the recently discovered early ``Li-6 plateau'', which (if confirmed), seriously challenges current ideas of cosmic ray nucleosynthesis.

18 pages, 9 figs. Invited Review in "Symposium on the Composition of Matter", honoring Johannes Geiss on the occasion of his 80th birthday (Grindelwald, Switzerland, Sept. 2006), to be published in Space Science Series of ISSI

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Cited by in corpus (10)

• Inheritance of solar short- and long-lived radionuclides from molecular clouds and the unexceptional nature of the solar system
• The $\nu$ process in the light of an improved understanding of supernova neutrino spectra
• Revisiting the pre-main-sequence evolution of stars I. Importance of accretion efficiency and deuterium abundance
• Revisiting the pre-main-sequence evolution of stars II. Consequences of planet formation on stellar surface composition
• An Introduction to Galactic Chemical Evolution
• Two distinct halo populations in the solar neighborhood. IV. Lithium abundances
• 11B and Constraints on Neutrino Oscillations and Spectra from Neutrino Nucleosynthesis
• The cosmological Lithium problem outside the Galaxy: the Sagittarius globular cluster M54
• The Abundance of Boron in Diffuse Interstellar Clouds
• Li isotopes in metal-poor halo dwarfs, a more and more complicated story