Study Proposes Detectable 'Fingerprints' in Sun from Engulfed Super-Earth

Planetary Engulfment Hypothesis

New research published in Monthly Notices of the Royal Astronomical Society proposes that the Sun may have engulfed a super-Earth-sized planet in its early stages. This event, according to the study, could have left lasting chemical signatures or 'fingerprints' deep within the Sun that are still detectable today.

Explaining Solar Discrepancies

Professor Mutlu Yildiz of Ege University stated that the ingestion of a super-Earth could help resolve long-standing differences between standard solar models and actual observations. These discrepancies include subtle variations in the Sun's internal structure and its notably low lithium abundance. The study suggests that a planet several times more massive than Earth could have caused these effects.

Planetary Survival and Chemical Imprints

The research indicates that a planet could survive its passage through the Sun's outer layers with minimal mass loss. This implies that planets might leave detectable chemical fingerprints inside their host stars long after they have been absorbed. The chemical composition of planets differs from the gas in protoplanetary discs, providing a basis for these unique signatures.

Addressing Helioseismic and Abundance Puzzles

For years, standard stellar evolution models have struggled to accurately reproduce certain helioseismic observations, specifically the sound-speed structure below the convection zone and its depth. Concurrently, the Sun exhibits a significant depletion of lithium on its surface. Researchers investigated whether these issues could stem from a common origin in the Sun's early chemical history, specifically the engulfment of a planet.

Methodology and Findings

The researchers utilized the MESA stellar-evolution code to test their hypothesis. They modeled various accretion histories and compared the resulting solar models against helioseismic constraints and surface element abundances. The study also considered alternative explanations involving the equation of state, opacity, and different turbulent and convective mixing prescriptions. The results support a scenario where the young Sun engulfed a planet.