Sun may have swallowed a super-Earth planet early in its history

The Sun may have consumed a super-Earth-sized planet billions of years ago during the chaotic early stages of the solar system's formation. Researchers propose that this ancient event left a lasting chemical fingerprint within the star that persists today.

Using the MESA stellar-evolution code to model the Sun's history, a research team found that the ingestion of a planet with a mass approximately five to 10 times that of Earth best aligns with current observations of the Sun's interior and chemical makeup. The study, published in the Monthly Notices of the Royal Astronomical Society, suggests that this planetary meal helps resolve two long-standing solar puzzles: the depletion of lithium on the Sun's surface and discrepancies in helioseismic observations regarding the depth of the convection zone and the sound-speed structure below it.

The chaos of early formation

Early solar system formation was characterized by extreme turbulence, a period where planetesimals frequently collided and planets migrated from their original orbits. Previous research has suggested that super-Earths—planets larger than Earth but smaller than Neptune—could have formed inside the orbit of Mercury and migrated further inward toward the star. This new study focuses on whether the Sun still carries observable evidence of such an event, addressing a significant gap in astronomical understanding: why our own solar system lacks a super-Earth despite their prevalence in other systems across the Milky Way.

Resolving solar contradictions

According to lead author Professor Mutlu Yildiz of Ege University, modeling the Sun's evolution and comparing those results with precise interior observations indicates that the ingestion of a super-Earth could explain the differences between standard solar models and actual observations. "Our new study suggests that a planet several times more massive than Earth may have fallen into the young sun and left a lasting chemical imprint deep inside it," Yildiz stated.

If confirmed, this finding would provide astronomers with a new method for investigating the early history of planetary systems by analyzing the chemical signatures of stars. It would not only explain the "missing" super-Earth in our system but also resolve contradictions between standard solar physics models and the observed internal structure of the Sun.

Future implications

While the MESA models provide a compelling fit for the data, the theory remains a proposal based on stellar modeling. Future research will likely focus on whether similar chemical fingerprints can be detected in other stars to determine if planetary engulfment is a common occurrence in the evolution of solar systems. For now, the study offers a potential solution to the mystery of the Sun's internal composition and the early architecture of our cosmic neighborhood.