The radiogenic heating of planets and the thermonuclear rate for the destruction of 40K in stars

The quantity of radioactive isotopes in a planet’s mantle and the evolution of its heating due to the isotopes’ radioactive decay determines the capability of that planet to develop geological features associated with a habitable environment, such as surface crust and plate tectonics. When our solar system was formed, large quantities of Potassium (K), a major element available in the interstellar medium at the time, got subsequently deposited inside our planet’s mantle and crust. Potassium’s long-lived radioactive isotope ⁴⁰K is still present in large quantities inside the planet. The beta particles that it emits while decaying have been heating up earth’s mantle for the last several billions of years and largely contribute to the habitable nature of Earth. Predicting the amount of ⁴⁰K enrichment in the solar system of an exoplanet would be key for a reliable calculation of the planet’s heating evolution and would allow us to make estimates on the likely existence or not of a habitable environment. Potassium, however, has a complex production and (destruction) mechanism in the cosmos. From a nucleosynthesis point of view, the uncertainty in the abundance of ⁴⁰K is associated with the reactions that create and destroy ⁴⁰K in stellar nucleosynthesis processes and the corresponding reaction rates. In my talk, I will discuss the importance of potassium in the context of exoplanet-related research, the origin of potassium in stars, the nuclear physics aspects that affect the existence of ⁴⁰K, and current experimental efforts to constrain relevant reaction rates.