Billions of years ago, our young Sun may have swallowed a planet with a mass roughly five to ten times that of Earth, according to a new study published in Monthly Notices of the Royal Astronomical Society. The research suggests scientists could detect the chemical "fingerprints" of this lost planet still buried inside the Sun today.
The findings, first reported by Gizmodo, also align with independent measurements of the Sun's internal structure, bringing astronomers closer to solving what has been described as a galactic case of cosmic cannibalism.
Mutlu Yildiz, the study's sole author and an astronomer at Ege University in Turkey, said the new research suggested a planet several times more massive than Earth could have fallen into the young Sun and left a lasting chemical trace deep within it.
Two Solar Puzzles
The study grew out of two separate mysteries. Standard solar models have generally struggled to reproduce real observations of the Sun's convective zone, the star's outermost layer.
Second, compared with other stars of similar size, the Sun's surface shows a noticeable shortage of lithium. That was puzzling because lithium, an element made of three protons, should be among the earliest elements to appear during stellar evolution.
Yildiz said he wondered whether these two problems might share a common origin in the Sun's early chemical history. He explained that because planets are made of material chemically distinct from the gas in a protoplanetary disk, he questioned whether an early planetary absorption could have left a chemical trace inside the young Sun.
Searching for the Best Fit
To test the idea, Yildiz used an open-source software module to model the star's evolution across a wide range of theories, examining different accretion scenarios that could have produced the Sun as it appears today.
The model that fit best was one in which the Sun absorbed a planet with the mass of a super-Earth billions of years ago. The resulting figures also matched known measurements of the Sun's internal structure and its lithium content.
The scenario could also help explain why, compared with similar star systems, our solar system does not have many planets the size of a super-Earth.
Yildiz added that while he had expected planetary absorption to affect solar structure, he had not anticipated that the calculations would converge on that specific super-Earth mass range, calling it one of the most interesting results of the study.
Not Yet Confirmed
Yildiz stressed that his calculations "reinforce the physical plausibility" that the Sun swallowed a super-Earth-sized planet, but that this is not confirmation that it actually happened.
Still, according to the paper, the results are an appealing candidate for a "key missing ingredient" in current solar and stellar models, meaning future theoretical and observational research may want to take the scenario into account.
Yildiz said the study raises the question of whether the Sun itself might still contain observable evidence that such an absorption really occurred, and said he believes it might. He said the next step is to check whether these traces can be independently detected.
