138La Anomaly in the Early Solar System

Details 138La Anomaly in the Early Solar System 138La Anomaly in the Early Solar System

Oct 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003apj...596l.109s&link_type=abstract

The Astrophysical Journal, Volume 596, Issue 1, pp. L109-L112.

Astronomy and Astrophysics

Astronomy

1

Nuclear Reactions, Nucleosynthesis, Abundances, Sun: Flares

Scientific paper

For every 1100 lanthanum atoms in the solar system, only one is 138La. Relative to this low abundance, even a tiny additional 138La made by irradiating its more abundant neighboring nuclides with energetic protosolar flare particles would cause a large, hence detectable, percentage increase in 138La. Such early solar irradiation can produce many now-extinct short-lived radio nuclides (e.g., 41Ca, 53Mn, and 26Al) and is the only way to make the newly discovered 10Be and the possibly detected 7Be, because stars destroy rather than produce Be. The alternative hypothesis to produce extinct nuclides is the injection of freshly synthesized radioactivity from a nearby asymptotic giant branch star or supernovae during solar system formation. Hoping to clarify the origin of extinct nuclides, we have been searching for 138La excess and its possible correlation with extinct nuclides. Here we report the detection of up to 0.6% (~7.5 σ) 138La excesses in five Allende calcium-aluminum-rich inclusions. Surprisingly, they do not correlate with 26Al, thus offering no support for making 26Al by early irradiation. Instead, 138La excess correlates with 50Ti excess. Current nucleosynthesis models produce 50Ti in a rare subset of Type I supernovae whose core underwent significant gravitational collapse before carbon deflagration. Our observed correlation thus suggests that 138La also came from these rare sources, perhaps in the mantle of the white dwarf, by reactions induced by the neutrino burst emitted during core neutronization. After the explosion, 138La was incorporated into Ti-rich dusts that later became the building material of our solar system.

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