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Low-mass asymptotic giant branch stars are among the most important polluters of the interstellar medium. In their interiors, the main component (A ≳ 90) of the slow neutron capture process (the s-process) is synthesized, the most important neutron source being the 13C(α,n)16O reaction. In this paper, we review its current experimental status, discussing possible future synergies between some experiments currently focused on the determination of its rate. Moreover, in order to determine the level of precision needed to fully characterize this reaction, we present a theoretical sensitivity study, carried out with the FUNS evolutionary stellar code and the NEWTON post-process code. We modify the rate up to a factor of 2 with respect to a reference case. We find that variations of the 13C(α,n)16O rate do not appreciably affect s-process distributions for masses above 3 M ⊙ at any metallicity. Apart from a few isotopes, in fact, the differences are always below 5%. The situation is completely different if some 13C burns in a convective environment: this occurs in FUNS models with M < 3 M ⊙ at solar-like metallicities. In this case, a change of the 13C(α,n)16O reaction rate leads to nonnegligible variations of the element surface distribution (10% on average), with larger peaks for some elements (such as rubidium) and neutron-rich isotopes (such as 86Kr and 96Zr). Larger variations are found in low-mass, low-metallicity models if protons are mixed and burned at very high temperatures. In this case, the surface abundances of the heavier elements may vary by more than a factor of 50.

Stardust grains recovered from meteorites provide highprecision\ud snapshots of the isotopic composition of the stellar\ud environment in which they formed1. Attributing their origin\ud to specific types of stars, however, often proves difficult.\ud Intermediate-mass stars of 4–8 solar masses are expected\ud to have contributed a large fraction of meteoritic stardust2,3.\ud Yet, no grains have been found with the characteristic isotopic\ud compositions expected for such stars4,5. This is a long-standing\ud puzzle, which points to serious gaps in our understanding of\ud the lifecycle of stars and dust in our Galaxy. Here we show that\ud the increased proton-capture rate of 17O reported by a recent\ud underground experiment6 leads to 17O/16O isotopic ratios that\ud match those observed in a population of stardust grainsfor\ud proton-burning temperatures of 60–80 MK. These temperatures\ud are achieved at the base of the convective envelope\ud during the late evolution of intermediate-mass stars of\ud 4–8 solar masses7–9, which reveals them as the most likely site\ud of origin of the grains. This result provides direct evidence\ud that these stars contributed to the dust inventory from which\ud the Solar System formed