Stellar Palimpsests: How We Read the History of Swallowed Planets ✦
Using chemical composition analysis of 113 sun-like stars, astronomers found three with an excess of elements indicating the engulfment of Earth-like planets. The mass of the engulfed material ranges from 7.5 to 33 Earth masses, and the frequency of such events is 1–3%. This is the first systematic search for planetary engulfment outside binary systems, opening a new way to study the co-evolution of stars and planets.
Every star is a living archive, and its spectrum a multilayered manuscript. Over billions of years, the history of the galaxy is written into it: the galactic chemical evolution of the Milky Way leaves a smooth trace in elemental abundances. But sometimes, on top of this layer, other lines appear — sharp, dramatic, telling of how a star swallowed its own planet. Deciphering such a palimpsest, separating the faint script of galactic processes from the vivid strokes of planetary catastrophes, is the task tackled by astronomers led by Cimo Cheng and Sharon Wang.
Instead of reading chemical anomalies "by eye," the authors applied the rigorous language of Bayesian statistics. They compared three scenarios: pure noise, predictable trends of galactic evolution, and a signal from planet ingestion. The key parameter — the added abundance of element X after full mixing in the convective zone — is described by an elegant equation relating the mass and composition of the swallowed body to the resulting chemical fingerprint. High-precision spectroscopy with the HARPS and MIKE instruments measured the abundances of 19 elements, and the nested sampling algorithm dynesty determined which model best fits the data.
Out of 113 stars, only three showed a clear signature of planetary ingestion: TOI-3342, HIP 101905, and TOI-2426. For the first two, the swallowed material resembled Earth in composition; for the third, primitive carbonaceous chondrites. The estimated masses — from 7.5 to 33 Earth masses — point not toward whole giant planets, but rather rocky super-Earths or massive cores. Notably, all three candidates have near-solar metallicity, hinting that ingestion is not tied to the overall chemical richness of the system.
These results turn single stars into full-fledged laboratories for studying exoplanetary dynamics. We are no longer chained to binary systems where one star serves as a control; now every solar analog can tell whether its planet met the fate of Icarus. Models of stellar evolution and atomic diffusion must be refined so as not to mistake a true signal for an illusion caused by element settling. And joint analysis with data on protoplanetary disks and nucleosynthesis will allow us to reconstruct the full history of chemical enrichment of stellar atmospheres.
We are closing in on an age-old mystery: why is the Sun depleted in refractory elements? Perhaps our own star once swallowed material, but in different proportions. Studying the frequency of planetary cannibalism provides a key to understanding how many systems are doomed to destruction long before we notice them. Upcoming ultra-stable spectrographs like ESPRESSO will turn the reading of stellar palimpsests into a routine tool for planetary scientists. And consider this: atoms born in stellar interiors and ejected during planetary ingestion ultimately end up in the interstellar medium, becoming part of new worlds — including our own.
🎯 If the Sun swallowed Earth, the iron content in its photosphere would increase by just 0.004% — almost imperceptible to most methods, but high-precision spectroscopy can catch such traces in other stars where the events were more massive.
🎬 In Stanisław Lem's 'Solaris,' the sentient ocean consumes people, but on a cosmic scale, entire planets become food for their suns, leaving behind only spectral shadows — chemical memories of perished worlds.