Solar Twins and Possible Solutions of the Solar and Jupiter Abundance Problems

Implications of the recently discovered systematic abundance difference between the Sun and two collections of `solar twins’ are discussed. The differences can be understood as an imprint on the abundances of the solar convection zone caused by the lock-up of heavy elements in the planets. Such a scenario also leads naturally to possible solutions of two other abundance peculiarities; 1) the discrepancy between photospheric abundances derived from accurate 3-D models of the solar photosphere and the abundance of heavy elements in the solar interior deduced from helioseismology, and 2) the abundance pattern of Jupiter, which can either–with great difficulty–be interpreted as a general and similar overabundance of both common elements such as carbon, nitrogen and sulphur and rare inert gases such as argon, krypton and xenon, or–much more simply–as an under-abundance of hydrogen.

💡 Research Summary

The paper addresses three long‑standing abundance anomalies – the slight metal deficiency of the Sun relative to solar twins, the disagreement between photospheric metal abundances derived from state‑of‑the‑art three‑dimensional (3‑D) solar atmosphere models and the higher metal content required by helioseismic inversions, and the puzzling composition of Jupiter’s atmosphere. The author proposes a single, physically motivated scenario: during the formation of the Solar System a substantial fraction of heavy elements (Fe, Si, Mg, etc.) was sequestered into the growing planets, especially the terrestrial planets and the gas giants. Because the solar convection zone contains only about 2 % of the Sun’s total mass, the removal of metals into planets can noticeably lower the metal mass fraction (Z) of the convection zone without appreciably affecting the bulk composition of the Sun’s interior.

Observationally, high‑resolution spectroscopy of solar twins shows that their photospheric metal abundances are on average ≈0.04 dex (≈10 %) higher than those of the Sun. The author argues that this offset is not an artifact of measurement or age differences but a direct imprint of planetary lock‑up: the Sun’s convection zone has been depleted relative to its twins because a comparable amount of metals resides in the planets.

Helioseismology, which probes the sound‑speed profile throughout the solar interior, requires a bulk metal fraction Z≈0.017, whereas 3‑D radiative‑hydrodynamic models of the solar photosphere give Z≈0.0122. If the convection zone is metal‑poor by roughly 10 % because of planetary sequestration, the interior can retain the higher Z demanded by helioseismology while the surface reflects the lower value measured spectroscopically. Simple mass‑balance calculations (convection‑zone mass ≈0.02 M⊙, metal mass locked in planets ≈10⁻³ M⊙) reproduce the observed 0.04 dex offset.

The same framework resolves the “Jupiter abundance problem.” Jupiter’s atmosphere appears enriched in carbon, nitrogen, sulfur, and the noble gases argon, krypton and xenon by factors of 2–3 relative to solar values. Traditional explanations invoke a universal enrichment mechanism that simultaneously enhances both volatile and refractory elements, a scenario that is difficult to reconcile with planet‑formation chemistry. The author instead suggests that Jupiter’s hydrogen abundance is modestly reduced relative to the Sun. If Jupiter’s H mass fraction is ≈15 % lower than solar, the remaining elements naturally appear over‑abundant by the observed factors, without requiring a special enrichment process for each element. This hydrogen‑deficit picture aligns with models in which rapid gas accretion onto the proto‑Jupiter occurs after most of the heavy elements have already been incorporated into the solid core and surrounding envelope.

In summary, the paper unifies three disparate abundance issues under the hypothesis that planetary formation removed a non‑negligible amount of heavy elements from the solar convection zone. This leads to (1) a modest metal depletion in the Sun’s outer layers relative to solar twins, (2) a reconciliation of photospheric and helioseismic metal abundances, and (3) a straightforward explanation for Jupiter’s apparent elemental over‑abundances as a consequence of a slightly hydrogen‑poor atmosphere. The proposed mechanism is appealing because it relies on well‑established aspects of planet formation and solar structure, and it makes testable predictions: precise abundance measurements of additional solar twins, refined helioseismic inversions, and improved models of Jupiter’s interior composition should all converge toward the values implied by the planetary lock‑up scenario. Future work involving high‑precision spectroscopic surveys and sophisticated planet‑formation simulations will be essential to confirm or refute this unified solution.