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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

The 22 Neðp; γÞ 23 Na reaction takes part in the neon-sodium cycle of hydrogen burning. This cycle affects the synthesis of the elements between 20 Ne and 27 Al in asymptotic giant branch stars and novae. The 22 Neðp; γÞ 23 Na reaction rate is very uncertain because of a large number of unobserved resonances lying in the Gamow window. At proton energies below 400 keV, only upper limits exist in the literature for the resonance strengths. Previous reaction rate evaluations differ by large factors. In the present work, the first direct observations of the 22 Neðp; γÞ 23 Na resonances at 156.2, 189.5, and 259.7 keV are reported. Their resonance strengths are derived with 2%-7% uncertainty. In addition, upper limits for three other resonances are greatly reduced. Data are taken using a windowless 22 Ne gas target and high-purity germanium detectors at the Laboratory for Underground Nuclear Astrophysics in the Gran Sasso laboratory of the National Institute for Nuclear Physics, Italy, taking advantage of the ultralow background observed deep underground. The new reaction rate is a factor of 20 higher than the recent evaluation at a temperature of 0.1 GK, relevant to nucleosynthesis in asymptotic giant branch stars.