The ams φ7Li = φ6Li as a function of kinetic energy by nucleon with total errors, as well as previous measures. Credit: Phys. Rev. Lett. (2025). DOI:
The origin of lithium (Li), the third element of the periodic painting, has long been wrapped in mystery. This element, commonly found in cosmic rays like two stable isotopes, 6Li and 7Li, is crucial to understanding the origins of the universe and the evolution of its chemical elements.
In a recent study, an international team of researchers used the alpha magnetic spectrometer (AMS-02) aboard the international space station to measure the cosmic radius flows 6Li and 7Li based on data accumulated from May 2011 to October 2023.
Based on the information of more than 2 million nuclei collected over 12 years, the team has formulated a hypothesis which strengthens the case of a possible origin of lithium while contesting another explanation previously accepted.
The results are published in Physical examination letters.
Lithium has at least three possible sources of origin: formed via more heavy cosmic nucleus collisions, created during the Big Bang, and produced from the decrease of Béryllium (7To be) in the stars with low mass or novae.
Despite its multiple origins, the Li nuclei are rare in our solar system but quite common in the cosmic rays. The two isotopes can trace their birth to the collisions of cosmic rays, although some studies suggest that 7Li could also have a primordial origin of the Big Bang. However, the amount of 7Li predicted by the nucleosynthesis of Big Bang does not correspond to what is observed in the stars or deduces cosmic ray data.
The AMS medium in time φ6Li (yellow) and φ7Li (cyan) multiplied by R˜ 2,7 with total errors depending on rigidity, as well as variations in flow time, yellow and cyan strips, respectively. Credit: Phys. Rev. Lett. (2025). DOI:
Over the past 50 years, several experiences have measured the 7Li /6Ratio Li, but there was a gap between the previous measurements of the lithium flow and the propagation models of current cosmic rays.
In addition, most of the isotopic lithium flow calculations were carried out below ~ 1.9 gv rigidity – a measure of the force of a particle resists to be deflected by magnetic fields, defined as a momentum by nuclear load.
The researchers of this study thought that examining it more closely these deviations in a broader range of rigidity could help to clarify the origin of Li isotopes. To achieve this, they made measurements with unprecedented precision in the rigidity range of 1.9 to 25 GV, collecting data from 9.7 × 105 6Li and 1.04 × 106 7Nuclei li.
The data have been accumulated over 12 years by AMS-02, a device composed of a surfed magnet which creates a uniform magnetic field to fold the paths of the cosmic particles loaded as it moves through five different detectors.
The results indicated that both 6Li and 7Li showed almost the same variations in time throughout the line of rigidity. Above ~ 4 GV, the time variations corresponded to those of other cosmic, helium, carbon, nitrogen and oxygen rays nuclei.
The isotopes have also shown the same dependence of rigidity greater than ~ 7 GV, which strongly supports the hypothesis that the two stable isotopes are produced from the collisions of cosmic nuclei heavier with the interstellar medium and excludes the presence of a significant main source of 7Li in the flow.
This study addresses the fundamental questions on the origin of the elements and opens the way to better understand the environment of cosmic rays, essential to advance the spatial exploration and the safety of astronauts.
More information:
M. Aguilar et al, properties of the isotopes of cosmic lithium measured by the alpha magnetic spectrometer, Physical examination letters (2025). DOI: 10.1103 / Physrevlett.134.201001
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