Evidence for multiple sources of 10Be in the early solar system

Daniel Kim Peel Wielandt, Kazuhide Nagashima, Alexander N. Krot, Gary R. Huss, Marina A. Ivanova, Martin Bizzarro

    Publikation: Bidrag til tidsskriftLetterForskningpeer review

    40 Citationer (Scopus)

    Abstract

    Beryllium-10 is a short-lived radionuclide (t 1/2 = 1.4 Myr) uniquely synthesized by spallation reactions and inferred to have been present when the solar system's oldest solids (calcium-aluminum-rich inclusions, CAIs) formed. Yet, the astrophysical site of 10Be nucleosynthesis is uncertain. We report Li-Be-B isotope measurements of CAIs from CV chondrites, including CAIs that formed with the canonical 26Al/27Al ratio of ~5 × 10–5 (canonical CAIs) and CAIs with Fractionation and Unidentified Nuclear isotope effects (FUN-CAIs) characterized by 26Al/27Al ratios much lower than the canonical value. Our measurements demonstrate the presence of four distinct fossil 10Be/9Be isochrons, lower in the FUN-CAIs than in the canonical CAIs, and variable within these classes. Given that FUN-CAI precursors escaped evaporation-recondensation prior to evaporative melting, we suggest that the 10Be/9Be ratio recorded by FUN-CAIs represents a baseline level present in presolar material inherited from the protosolar molecular cloud, generated via enhanced trapping of galactic cosmic rays. The higher and possibly variable apparent 10Be/9Be ratios of canonical CAIs reflect additional spallogenesis, either in the gaseous CAI-forming reservoir, or in the inclusions themselves: this indicates at least two nucleosynthetic sources of 10Be in the early solar system. The most promising locale for 10Be synthesis is close to the proto-Sun during its early mass-accreting stages, as these are thought to coincide with periods of intense particle irradiation occurring on timescales significantly shorter than the formation interval of canonical CAIs.
    OriginalsprogEngelsk
    ArtikelnummerL25
    TidsskriftThe Astrophysical Journal Letters
    Vol/bind748
    Udgave nummer2
    Antal sider7
    ISSN2041-8205
    DOI
    StatusUdgivet - 1 apr. 2012

    Citationsformater