The Sun May Have Swallowed a Super-Earth and Still Hides the Evidence

Our star’s early history may involve a violent planetary meal. New research indicates that the infant sun swallowed a super-Earth planet billions of years ago, leaving a lasting chemical and structural signature deep within its interior. Super-Earths frequently appear in other planetary systems, making the inner solar system’s lack of such a world a lingering puzzle that this scenario helps resolve. The author of the study gave the vanished world a nickname: Dev Dilek, a Turkish phrase meaning “Great Wish.”

Young stars like the sun during its infancy are surrounded by vast flattened clouds of gas and dust called protoplanetary discs, where substantial amounts of material can move between the disc and the star. Since planets are made of material that is chemically different from the gas in the disc, the researchers wondered whether the early engulfment of a planet could have left a chemical signature inside the young sun.

Mutlu Yildiz and Ege University Simulations

For decades, standard solar models have struggled to align with precise interior observations. Mutlu Yildiz, an astronomer at Ege University in Turkey, turned to computer modeling to investigate whether early stellar feeding could account for these persistent discrepancies. Using a stellar simulation program called MESA, the research team modeled two early feeding episodes for the young sun: an intake of heavy-element-rich material, standing in for a swallowed planet, followed by a batch of gas unusually poor in heavy elements, representing leftover disk material after planets had already formed. By adjusting how much was added, when, and how it settled, the researchers tested different planetary engulfment scenarios to see how a foreign body would alter a growing star.

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, Mutlu Yildiz, of Ege University, Turkey, said in a statement.

The simulations revealed that the best-fitting models point to an engulfed planet weighing between five and ten times the mass of Earth, with a new study suggesting the sun may have swallowed a planet about 5.6 times Earth’s mass early in its history, or about a third of Neptune’s mass. Physics checks suggest a compact rocky planet could have survived the plunge into the sun largely intact. This ingested world would have formed within the protoplanetary disc surrounding the infant sun before migrating inward and colliding with the star.

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, said Professor Yildiz. That was one of the most interesting outcomes of the study.

Solving Solar Puzzles and Lithium Depletion

Helioseismic data—sound waves traveling through the sun that act like an internal ultrasound—reveals precise details about the star’s interior. Standard computer models have consistently failed to match three major observations simultaneously: the speed of sound at various depths, the exact boundary of the sun’s churning outer layer, and the surface mix of hydrogen, helium, and heavier elements.

Swallowing a super-Earth leaves a heavy-element-rich layer just beneath the sun’s churning outer convection zone. This hidden layer reshapes the star’s internal sound-speed structure and accounts for long-standing deviations from standard evolutionary models.

“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, including subtle changes in the sun’s internal structure and its depleted lithium abundance,” Yildiz said. We were interested in whether these problems might have a common origin in the early chemical history of the sun.

The event also addresses the sun’s mysterious shortage of lithium. The same scenario matches the sun’s mysterious lithium shortage if the engulfed planet weighed 4.6 to 5.8 Earth masses.

Next Steps for Independent Detection

While the findings rest on computer modelling and unexplained solar features, researchers emphasize that the physical evidence may still reside within our star. The study leaves open the possibility that something else, other than this violent collision with the sun, may explain the discrepancies in measurements of the sun’s interior and its lithium content. The team’s model doesn’t need a planet to have been totally engulfed by the sun. Currently, this idea is based on computer modelling and unexplained solar features, but the researchers think that the predicted structural and chemical signature of a planetary engulfment could still be found.