Our Sun May Have Secretly Swallowed a Massive Super-Earth Planet Billions of Years Ago, Study Suggests

Billions of years ago, our young sun may have consumed a planet several times the mass of Earth, and the chemical fingerprints of that ancient collision could still be detectable deep inside the star today, according to new research published in the journal Monthly Notices of the Royal Astronomical Society.

The study, authored by Mutlu Yildiz, an astronomer at Ege University in Turkey, presents a model suggesting the sun engulfed a "super-Earth-mass" planet — one estimated at five to 10 times the mass of Earth — early in its history. The finding offers a possible explanation for two longstanding puzzles in solar science that conventional models have struggled to fully resolve.

"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 said in a statement.

Two mysteries in search of a common cause

The research grew out of separate, seemingly unrelated problems in solar astronomy. The first involves the sun's convection zone, the star's outermost layer, where standard models have consistently had difficulty matching actual observational data. The second concerns lithium, an element that should be among the earliest to survive largely intact through a star's evolution, yet the sun's surface shows a notable lithium deficiency compared with other stars of similar size and age.

Yildiz set out to determine whether these two unrelated anomalies might share a single origin. "We were interested [in] whether these problems might have a common origin in the early chemical history of the Sun," Yildiz said. "Since planets are made of material that is chemically different from the gas in the disc, we wondered whether the early engulfment of a planet could have left a chemical signature inside the young Sun."

Modeling a cosmic collision

To test the idea, Yildiz used an open-source stellar evolution module to run through a wide range of possible accretion scenarios, essentially testing different combinations of events that could have produced the sun as it appears today. Among the scenarios tested, the one that best matched observed data involved the young sun consuming a super-Earth-mass planet.

The resulting numbers lined up closely with existing measurements of the sun's internal structure and its surface lithium content, lending additional weight to the scenario. Yildiz noted that the precision of the result came as something of a surprise even to him.

"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. "That was one of the most interesting outcomes of the study."

A possible clue to the makeup of our solar system

Beyond addressing the lithium and convection-zone puzzles, the engulfment scenario may also help explain another peculiar feature of our solar system: the conspicuous absence of super-Earth-sized planets, a category common in many other star systems observed by astronomers. If an early super-Earth once orbited close to the young sun and was ultimately pulled in and destroyed, its disappearance could account for why no planet of that size exists in our solar system today.

Evidence, not proof

Yildiz was careful to frame the findings as evidence supporting a plausible scenario rather than definitive confirmation that the event occurred. In the paper, he wrote that the calculations "strengthen the physical plausibility" of the sun having swallowed a super-Earth-sized planet, while stopping short of claiming certainty. The paper describes the scenario as a promising candidate for the "key missing ingredient" that has been absent from existing solar and stellar models.

Yildiz said the next phase of research will focus on searching for more direct, independently verifiable evidence of the ancient engulfment buried within the sun's structure. "Our paper asks whether the Sun itself could still carry observable evidence that such an engulfment actually happened, and we believe it could," Yildiz said. "The next step is to see if these fingerprints can be independently detected."

Why planetary engulfment matters to astronomers

Stellar engulfment of planets is not considered a rare phenomenon in the broader universe. Astronomers have observed direct evidence of stars consuming nearby planets in other systems, and theoretical models suggest such events are a natural, if violent, part of how planetary systems evolve and stabilize over billions of years. Planets that form too close to their host star, or whose orbits become unstable over time due to gravitational interactions with other bodies, can spiral inward and eventually be pulled apart and absorbed by the star's immense gravity and heat.

What makes the sun's case distinctive, according to the new research, is the possibility that this kind of event left behind detectable chemical evidence that has persisted for billions of years, offering scientists a potential window into the sun's earliest, most chaotic period of formation.

The study adds to a growing body of research using increasingly sophisticated stellar modeling techniques to probe the sun's distant past, a period that remains difficult to study directly given how much the star's structure and composition have evolved since its formation roughly 4.6 billion years ago. If future observational work is able to confirm the specific chemical signatures Yildiz's model predicts, it could mark a significant step toward resolving decades-old questions about the sun's internal chemistry and, more broadly, about how the current architecture of our solar system came to be.

For now, the case remains open, but the new modeling gives astronomers a specific and testable hypothesis to pursue in the search for what really happened inside our solar system's earliest, most turbulent chapter.