Unlocking insights into the Sun’s evolutionary history

Ion decay sheds light on solar neutrino flux.

Detecting neutrinos

The Sun, the life-sustaining engine of Earth, generates energy through nuclear fusion while releasing a continuous stream of neutrinos—particles that serve as messengers of its internal dynamics. Although modern neutrino detectors unveil the Sun’s present behaviour, significant questions linger about changes in the sun’s release of neutrinos over the course of its existence.

To address these uncertainties, the LORandite EXperiment (LOREX) stands as the final bastion of neutrino geochemical projects. This low-energy solar neutrino detector aims to measure solar neutrino flux averaged since the formation of the sun.

Ion decay

Neutrinos produced in our Sun interact with thallium (Tl) atoms, present in the lorandite mineral (TlAsS2), and convert them into lead (Pb) atoms. The isotope 205Pb is particularly interesting due to its long half-life time of 17 million years, making it essentially stable over the 4 million years timescale of the lorandite ore. As it is currently not feasible to directly measure the neutrino cross-section on 205Tl, researchers came up with a clever method to measure the relevant nuclear physics ingredients: they exploited the fact that fully ionized 205Tl81+ spontaneously decays by bound-state beta decay to 205Pb81+, delivering the information needed for the determination of the neutrino cross section.

The international team discovered that the half-life of 205Tl81+ beta decay was measured as 291 (+33/-27) days. The experiment was only possible thanks to the unique capabilities of the Experimental Storage Ring at GSI in Germany.

This achievement lays the nuclear physics foundation for the LOREX project, which aims to unlock insights into the Sun’s evolutionary history and its connection to Earth’s climate over millennia.

Dr Ragandeep Singh Sidhu, a key contributor to the study and the first author of the publication, highlighted its significance:

This experiment highlights how a single, albeit challenging, measurement can play a pivotal role in addressing significant scientific questions related to solar neutrinos.

The publication is dedicated to the memory of late colleagues Fritz Bosch, Roberto Gallino, Hans Geissel, Paul Kienle, Fritz Nolden, and Gerald J. Wasserburg, whose contributions were integral to the success of this project.