TY - JOUR
T1 - Evidence for multiple sources of 10Be in the early solar system
AU - Wielandt, Daniel Kim Peel
AU - Nagashima, Kazuhide
AU - Krot, Alexander N.
AU - Huss, Gary R.
AU - Ivanova, Marina A.
AU - Bizzarro, Martin
PY - 2012/4/1
Y1 - 2012/4/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=84858733209&partnerID=8YFLogxK
U2 - 10.1088/2041-8205/748/2/L25
DO - 10.1088/2041-8205/748/2/L25
M3 - Letter
AN - SCOPUS:84858733209
SN - 2041-8205
VL - 748
JO - The Astrophysical Journal Letters
JF - The Astrophysical Journal Letters
IS - 2
M1 - L25
ER -