Fingerprints of the protosolar cloud collapse in the Solar System I: Distribution of presolar short-lived ${}^{26}$Al

Abstract

The short-lived radionuclide ${}^{26}$Al is widely used to determine the relative ages of chondrite components and timescales of physical and thermal events that attended the formation of the Solar System. However, an important assumption for using ${}^{26}$Al as a chronometer is its homogeneous distribution in the disk. Yet, the oldest components in chondrites, the Ca-Al-rich inclusions (CAIs), which are usually considered as time anchors for this chronometer, show evidence of ${}^{26}$Al/${}^{27}$Al variations independent of radioactive decay. Since their formation epoch may have been contemporaneous with the collapse of the parent cloud that formed the disk, this suggests that ${}^{26}$Al was heteregeneously distributed in the cloud. We model the collapse of such an heterogeneous cloud, using two different ${}^{26}$Al distributions (monotonic and non-monotonic), and follow its re-distribution in the first condensates and bulk dust that populate the forming disk. We find that CAIs inherit the ${}^{26}$Al/${}^{27}$Al ratio of the matter infalling at the time of their formation, so that variations of ${}^{26}$Al/${}^{27}$Al among primordial CAIs can be accounted for, independently of radioactive decay. The prevalence of a canonical ratio among them and its necessity for the differentiation of the first planetesimals suggest a (monotonic) scenario where ${}^{26}$Al sharply rose relatively close to the center of the protosolar cloud and essentially remained at a high level outward (rather than decreased since). As the ${}^{26}$Al abundance would be relatively homogeneous after cessation of infall, this would warrant the use of the Al-Mg chronometer from the formation of "regular" CAIs onward, to chondrules and chondrite accretion.

ArXiv version

References in corpus (3)

• Triggered Star Formation Inside the Shell of a Wolf-Rayet Bubble as the origin of the Solar System
• Fingerprints of the protosolar cloud collapse in the Solar System II: Nucleosynthetic anomalies in meteorites
• Protoplanetary dust porosity and FU Orionis Outbursts: Solving the mystery of Earth's missing volatiles

Cited by in corpus (7)

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• Mixing is easy: New insights for cosmochemical evolution from pre-stellar core collapse
• Comparison between core-collapse supernova nucleosynthesis and meteoric stardust grains: investigating magnesium, aluminium, and chromium
• Depletion of Moderately Volatile Elements by Open-System loss in the Early Solar Nebula
• Global Modeling of Nebulae With Particle Growth, Drift, and Evaporation Fronts. III. Redistribution of Refractories and Volatiles
• Chondrule Formation During Low-Speed Collisions of Planetesimals: A Hybrid Splash-Flyby Framework