A study led by Mutlu Yildiz of Ege University suggests the Sun may have consumed a super-Earth 5 to 10 times Earth’s mass billions of years ago, leaving chemical imprints that could resolve long-standing solar physics mysteries. The research, published in the Monthly Notices of the Royal Astronomical Society, uses stellar-evolution models to link the event to the Sun’s low lithium levels and internal structure discrepancies.
The Sun, our solar system’s central star, may have once devoured a super-Earth—a rocky planet 5 to 10 times more massive than Earth—leaving behind chemical traces that could explain two enduring puzzles in solar physics. A study by Mutlu Yildiz, an astronomer at Ege University in Turkey, proposes that this cosmic event, which occurred in the star’s early history, could account for the Sun’s unusually low lithium abundance and inconsistencies between helioseismic measurements and standard solar models.
The Study’s Key Findings
Yildiz’s research, published in the Monthly Notices of the Royal Astronomical Society, used the MESA stellar-evolution code to simulate the Sun’s early accretion history. The team found that a single engulfment scenario could simultaneously explain two anomalies: the Sun’s depleted lithium levels and the mismatch between helioseismic data and theoretical models of its internal structure. We thought planetary engulfment might affect the solar structure but did not expect the calculations to converge on such a specific super-Earth mass range,
Yildiz said, highlighting the study’s unexpected precision.
The Sun’s lithium abundance has long baffled astronomers. Lithium, an element made of three protons, should be among the earliest products of stellar evolution. Its relative absence on the Sun has puzzled astronomers for decades. Yildiz’s team suggests that the ingestion of a super-Earth could have introduced chemical differences into the Sun’s interior, altering its composition. Since planets are made of material that is chemically different from the gas in the disk, we wondered whether the early engulfment of a planet could have left a chemical signature inside the young Sun,
he explained.
How the Sun’s ‘Fingerprints’ Might Be Detected
The study’s models indicate that the super-Earth would have survived passing through the Sun’s outer layers, losing only a fraction of its mass. This scenario would have left a lasting chemical imprint deep inside
the star, according to Yildiz. The engulfed planet’s material would have mixed into the Sun’s interior, potentially creating detectable anomalies in helioseismic measurements—sound waves that reveal the star’s internal structure.
Helioseismology has revealed discrepancies in the Sun’s sound-speed profile and the depth of its convection zone. The study’s models align with these observations, suggesting that the super-Earth’s ingestion could resolve these gaps. By modelling the sun’s evolution and comparing the results with precise observations of its interior, we find that the ingestion of a super-Earth could help explain long-standing differences between standard solar models and observations,
Yildiz said.
The next step is to search for these predicted “fingerprints.” Scientists aim to detect subtle chemical and structural signatures using advanced helioseismic techniques. The next step is to see if these fingerprints can be independently detected,
Yildiz noted. If confirmed, this would provide strong evidence that the Sun consumed a planet billions of years ago.
Implications for Planetary System Evolution
If validated, the study would reshape our understanding of planetary system formation. Many other star systems host large super-Earths, yet our solar system does not. The research suggests that such planets may have formed inside Mercury’s orbit and migrated inward, possibly falling into the Sun. The idea that the Sun once engulfed a planet is perfectly consistent with the chaotic state of early planetary system formation,
Yildiz said. During that time, the orbits of all celestial bodies were unstable, and collisions were common.
The study also addresses why super-Earths are rare in our solar system. If this theory can be verified, it will be able to explain the Sun’s quirks and will also overturn the existing understanding of planetary system evolution,
Yildiz noted. It implies that our solar system once harbored super-Earths, which were later lost to the Sun. It would mean that our solar system once had super-Earths, but they were lost to the star that now sustains us,
Yildiz said.
While definitive proof remains elusive, the study’s findings offer a compelling framework for future research. While it may not be possible to definitively prove the Sun swallowed a planet, if the predicted fingerprints can be independently detected, it would provide strong evidence for such an event happening billions of years ago,
Yildiz added. The search for these signatures continues, with scientists hopeful that helioseismic advancements will soon shed light on this cosmic mystery.
