No abstract

No abstract

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

Among the reactions involved in the production and destruction of deuterium during Big Bang Nucleosynthesis, the deuterium-burning D(p,γ) 3 He reaction has the largest uncertainty and limits the precision of theoretical estimates of primordial deuterium abundance. Here we report the results of a careful commissioning of the experimental setup used to measure the cross-section of the D(p,γ) 3 He reaction at the Laboratory for Underground Nuclear Astrophysics of the Gran Sasso Laboratory (Italy). The commissioning was aimed at minimising all sources of systematic uncertainty in the measured cross sections. The overall systematic error achieved (< 3%) will enable improved predictions of BBN deuterium abundance.