A possible planetary imprint inside the Sun
The Sun may preserve evidence of having consumed a rocky planet early in its history, according to a study published in Monthly Notices of the Royal Astronomical Society. The researchers say models in which the young Sun engulfed a super-Earth can simultaneously reproduce several features that standard solar-evolution calculations have struggled to match.
The work, reported on September 13 by the Royal Astronomical Society, does not establish that such a planet existed or was swallowed. It identifies a testable scenario: a world roughly five to ten times Earth’s mass could have altered the Sun’s chemistry and internal structure in ways that remain detectable billions of years later.
Mutlu Yildiz of Ege University used the MESA stellar-evolution code to compare different histories of material falling into the Sun. The resulting models were checked against helioseismic measurements, which use oscillations at the solar surface to infer conditions inside the star, and against observed chemical abundances. Alternative changes to opacity, the equation of state and prescriptions for mixing were also explored.
The planet-ingestion scenario helped the calculations match the observed depth of the Sun’s convection zone, subtle differences in sound speed below that region and the unusually low abundance of lithium at the surface. The convergence on a super-Earth-sized object was a result of the modelling rather than a directly observed planet.
Evidence would need independent detection
The proposed mechanism begins with the chemically distinct material found in a rocky planet. If that material entered the young Sun, it could have changed the star’s composition while transport and mixing redistributed elements through its layers. The researchers also calculated that an infalling planet could pass through the Sun’s outer layers while losing relatively little mass, allowing it to reach deeper regions and leave a longer-lived signature.
The idea connects with earlier research suggesting that super-Earths could have formed inside Mercury’s present orbit and migrated inward through the protoplanetary disc. Our solar system lacks the close-orbiting super-Earths common around other stars, but that absence alone is not proof that the Sun consumed one. The earlier work offered a possible route; the new study asks whether the Sun’s present properties are consistent with the outcome.
Yildiz said the next step is to seek the predicted structural and chemical fingerprints independently through helioseismic observations or other measurements. A successful detection would strengthen the engulfment interpretation, while a failure could narrow or rule out parts of the model.
The study therefore reframes several solar puzzles as potentially linked rather than claiming a recovered history of a vanished planet. Its value will depend on whether the proposed internal signature distinguishes planetary ingestion from other changes to solar physics and whether other researchers can reproduce the result.
