The Timing of Potential Last Nucleosynthetic Injections into the Protosolar Molecular Cloud Inferred from 41Ca–26Al Systematics of Bulk CAIsOPEN ACCESS 

Yaray Ku, Michail I. Petaev, and Stein B. Jacobsen

The Astrophysical Journal Letters, Volume 931, Number 1
Published: 23 May 2022


“Short-lived radionuclides (SLRs) provide important information about the chronology of the early solar system. Among them, 41Ca, due to its decay to 41K with a half-life of only 0.1 Ma, is particularly valuable in constraining the timescales and origins of both SLRs and the formation of the oldest solar system materials, the Ca–Al-rich inclusions (CAIs). The initial abundance of 41Ca in the solar system, expressed as the (41Ca/40Ca) Iratio, is the key to unveiling the origin of this nuclide. Here, we report a new solar system (41Ca/40Ca)I ratio of 2.0×10−8 derived from the K isotope compositions of two CAIs. This new ratio is about four times higher than the previous value inferred from a mineral isochron. Such a high (41Ca/40Ca) Iratio in the CAIs exceeds that expected for the protosolar molecular cloud by ∼1000×, implying very late injection of the 41Ca (and possibly other SLRs) into the protosolar molecular cloud. The correlated enrichments of 41Ca and 26Al in the bulk CAI samples hint at a common stellar origin of both SLRs. The injection time estimated from our new data depends on the stellar source—it ranges from 0.6 Ma for a Wolf–Rayet wind to 1.0 Ma for a TP-AGB star ejecta.”