- 1Bavarian Geoinstitute (BGI), University of Bayreuth, Bayreuth, Germany (thomas.trueman@uni-bayreuth.de)
- 2HUN-REN Research Centre for Astronomy and Earth Sciences (CSFK), Konkoly Observatory, Budapest, Hungary
- 3MTA Centre of Excellence, Budapest, Hungary
- 4NuGrid Collaboration, http://www.nugridstars.org
- 5Department of Geological Sciences, University of Colorado, Boulder, Colorado, USA
The long-lived radioisotope 40K (half-life of 1.248 Gyr) is a dominant heating source driving mantle convection and volcanic activity in rocky exoplanets. Whilst the initial radiogenic heat budget of 40K in the Solar System can be inferred from meteoritic chronology, it is unclear whether the 40K/K ratio is consistent with galactic chemical evolution (GCE) or if it comes mostly from a single local stellar ejecta event. In this work, we use the OMEGA+ GCE code to predict the 40K/K abundance ratio in the interstellar medium (ISM) as a function of Galactic age. Our GCE models assume that some fraction of massive stars undergo a C-O shell merger, which significantly boost the production of light odd-Z elements in the pre-explosive yields [1, 2, 3] and are necessary to reproduce non-local thermodynamic equilibrium spectroscopic abundances. We incorporate merger yields from the literature [4], spanning a range of initial masses and metallicities into two massive-star yield sets [5, 6] using a self-consistent approach without needing to modify global GCE parameters. Our results allow us to determine confidence intervals (CIs) for the 40K/K ratio in the ISM as a function of Galactic age; these CIs take into account the intrinsic metallicity scatter in the solar neighbourhood, different fractions of massive stars that undergo C-O mergers, stellar yield uncertainties, and observationally constrained initial GCE parametrisations. From our CIs, we quantify the likelihood that the Solar System's 40K budget was inherited from the Galactic background. More generally, our results can be applied to planet-hosting stars of known metallicity, however, the CIs become dominated by stellar age uncertainties.
References
[1] L. Roberti, M. Pignatari, A&A, 703, id.L15, 8 pp. (2025)
[2] J. Issa, F. Herwig, S. J. Mojzsis, et al., Apj, 997:314 (10pp), (2026)
[3] C. Ritter, R. Andrassy, B. Côté, MNRAS: Letters, 474, Issue 1, p.L1-L6, (2018)
[4] C. Ritter, F. Herwig, S. Jones, et al, MNRAS, 480, Issue 1, p.538-571, (2018)
[5] K. Nomoto, C. Kobayashi, N. Tominaga, ARA&A, 51, 457, (2013)
[6] M. Limongi, A. Chieffi, ApJ, 647, 483, (2018)
How to cite: Trueman, T. C. L., Mojzsis, S. J., and Pignatari, M.: Galactic Chemical Evolution of 40K as a heat source for rocky exoplanets, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-1013, https://doi.org/10.5194/epsc2026-1013, 2026.
