The Sun may still bear traces of a swallowed super-Earth
Stellar modelling suggests a planet five to 10 times the mass of Earth may have been engulfed by the young Sun, but the hypothesis remains unproven.
The young Sun may have swallowed a super-Earth, leaving chemical and structural signatures that could still be detected in the solar interior, according to research reported by the Royal Astronomical Society.
The study, published in Monthly Notices of the Royal Astronomical Society, used the MESA stellar-evolution code to model different accretion histories and compare them with observations of the Sun’s interior and surface composition.
The modelling favours an engulfed planet with a mass between five and 10 times that of Earth. Researchers said the scenario could help explain discrepancies between standard solar models and helioseismic observations, including the structure beneath the Sun’s convection zone and the depth of that zone.
It may also help account for the Sun’s unusually low surface lithium abundance. The researchers said a planet of that size could pass through the Sun’s outer layers while losing relatively little mass, potentially leaving detectable traces long after the engulfment.
The findings build on earlier research proposing that super-Earths could form inside Mercury’s orbit and migrate towards the young Sun. That work established a possible pathway, but did not show that an engulfment occurred.
The latest study does not prove the Sun swallowed a planet. The researchers say independent detection of the predicted chemical or structural fingerprints through helioseismic or other observations would be needed to provide strong evidence.
