The detection of 26Al provides evidence of ongoing nucleosynthesis in the Universe

The short-lived radioisotope 26Al (t1/2 =0.7 Myr) plays a unique role in our understanding of the origin of the chemical elements in the Universe. As shown in Figure 1, its presence can be directly observed in our Galaxy by its decay radiation, providing evidence of ongoing nucleosynthesis and giving precious hints concerning the main stellar sites where it’s produced. These are mainly massive stars, as the emission peaks are from either massive star-rich parts of the Galaxy or from supernova remnants. Moreover, 26Al is observed also in meteorites, where an excess of its daughter isotope 26Mg suggests that 26Al was injected into the Solar System just before its formation.

Figure 1: A map of the galactic 26Al decay gamma radiation signature at 1.8 MeV. Credits: the COMPTEL Collaboration

On the other hand, simulations over the last years of the stellar sites producing 26Al were weakened by significant nuclear uncertainties. However, very recently an international group of nuclear physicists and astrophysicists re-evaluated the rates of the two main nuclear reactions responsible for the destruction of 26Al inside stars, based on a very recent high-precision study performed at CERN, where nine resonance strengths were measured for the first time. These new reaction rates have greatly reduced uncertainties, which is highly beneficial to carry out an effective comparison between stellar models and observations and pinning down the main uncertainties stemming out of the stellar modeling side. Moreover, they showed how the implementation of the new rates in stellar models visibly improves the agreement of computer models with observables, especially between AGB models and presolar grains data.

References

  • Battino et al.; Monthly Notices of the Royal Astronomical Society, Volume 520, Issue 2, pp.2436-2444 (2023); DOI:10.1093/mnras/stad106
  • A Vasini, F Matteucci, E Spitoni, Chemical evolution of 26Al and 60Fe in the Milky Way, Monthly Notices of the Royal Astronomical Society, Volume 517, Issue 3, December 2022, Pages 4256–4264, https://doi.org/10.1093/mnras/stac2981
If you like our job, and wish to support, please send a donation