'Fingerprints' inside the sun could reveal if it once swallowed a planet

An artist's impression of a star engulfing a planet. The blue line traces the path of the planet as it spirals toward the star and ultimately collides with it. Credit: NASA, ESA, CSA, Ralf Crawford (STScI), License type Attribution (CC BY 4.0) A new study suggests that the sun may have engulfed a super-Earth-sized planet early in its history, leaving detectable chemical imprints inside the sun. Researchers used the MESA stellar-evolution code to model the sun's evolution and found that a super-Earth around five to 10 times the mass of Earth could have fallen into the young sun, explaining discrepancies in solar models. The study also found that such a planet could survive its passage through the sun's outer layers while losing very little mass, suggesting that planets may leave detectable fingerprints inside their host stars long after they have disappeared. Two solar puzzles align: one is the sound-speed structure just below the convection zone, and the other is the depth of the solar convection zone. These puzzles may have a common origin in the early chemical history of the sun, and the study suggests that planetary engulfment could be responsible for these differences. The researchers tested various accretion histories and compared the resulting solar models with helioseismic constraints and surface abundances, finding that a super-Earth around five to 10 times the mass of Earth could explain the observed solar structure and lithium depletion. The study's findings support the idea that planetary engulfment may have occurred billions of years ago, and if the predicted structural and chemical signature could be independently identified through helioseismic or other observations, it would provide strong evidence for such an event. The study also cites previous research suggesting that a super-Earth could have formed inside the orbit of Mercury and migrated inward, potentially falling into the young sun. However, the earlier work did not require that such a planet was ultimately swallowed by the sun. The study's results favor a scenario in which the young sun engulfed a super-Earth around five to 10 times the mass of Earth, and the modeling does more than explain one puzzle, simultaneously matching several independent measurements of the sun, including its interior and its unusually low lithium abundance. The study's findings suggest that planetary engulfment may be a solution to solar-model discrepancies and could have implications for planetary systems.

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