In Search of Traces of Planet Engulfment: Bayesian Analysis of Chemical Composition of Solar Analogues ✛ ✦
Context
Planets can fall into their stars due to tidal effects or dynamical instability, and if the accreted material mixes into the convective zone, it leaves a measurable chemical fingerprint in the photosphere. Previous searches for such signatures focused on co-natal binary systems, where one star serves as a control, but most stars lack suitable twins. Solar analogues and twins, which allow high-precision differential analysis relative to the Sun, open up the possibility of searching in single stars. This is critically important for understanding the evolution of exoplanetary systems and the frequency of catastrophic engulfment events.
Methods
For each of the 113 stars (79 from the Bedell catalog and 42 from the PASTA survey), differential abundances of 19 elements (from C to Zn) were obtained via high-precision spectroscopy with the HARPS and MIKE instruments. The researchers developed a Bayesian framework comparing three families of models: a flat pattern (purely random scatter), two models of Galactic chemical evolution (GCE), and a planet engulfment model assuming instantaneous mixing of accreted material in the star's convective zone. For the accreted material, two reference compositions were considered: the bulk Earth composition and CM chondrites. Using the nested sampling algorithm dynesty, Bayesian factors were computed, and significance thresholds were calibrated on synthetic data (parametric bootstrap) to control false positives.
Results
Under strict selection criteria in the configuration with a solar baseline and using [X/Fe] (which suppresses atomic diffusion effects), three robust candidates were identified: TOI-3342, HIP 101905, and TOI-2426. Their abundance patterns are best described by the engulfment model: TOI-3342 and HIP 101905 show an excess of elements characteristic of Earth composition (accreted masses of 16±4 and 7.5±1.0 Earth masses, respectively), while TOI-2426 matches CM chondrites (33+9/−7 Earth masses). Another 14 stars are flagged as optimistic candidates under less conservative conditions. None of the candidates had an accreted mass exceeding 35 M⊕, significantly below the total solid mass in the minimum solar nebula. The overall detection rate of robust engulfment signatures was about 2.7% (1–3% considering subsamples), consistent with previous estimates for binary systems.
Implications
The results prove that chemical fingerprints of planet engulfment can be detected not only in binary systems but also among single stars, provided alternative processes such as Galactic chemical evolution are carefully modeled. This paves the way for statistical studies of engulfment frequency in a broad population, including stars with known planets. The work also shows that the traditional method based on the slope of abundance versus condensation temperature (Tc slope) is insufficient for identifying engulfment, as it collapses a multidimensional pattern into a single number, losing information. The proposed Bayesian approach preserves the full abundance picture and can distinguish between scenarios.
Future development
Future research should focus on expanding the sample with uniform high-precision measurements to refine the event frequency and its dependence on planet presence. Improved models of stellar evolution and atomic diffusion, which can mimic or mask engulfment signals, are needed. Developing more detailed composition templates (e.g., accounting for planet differentiation) and joint analysis with system dynamics data will help distinguish engulfment from planet formation effects. Direct confirmation of candidates with additional observations on ultra-stable spectrographs like ESPRESSO, and searching for associated markers (lithium anomalies, rotation), will strengthen the method's reliability.
Impact
The method will impact exoplanetology by providing a new way to assess the fate of planetary systems, and stellar evolution theories by refining mixing processes in convective zones. The results are also important for cosmochemistry and Galactic archaeology, helping to separate planetary signals from nucleosynthesis effects.
Next steps
A key step is conducting a homogeneous spectroscopic survey of a large sample of solar analogues with and without known planets, using instruments like ESPRESSO at the VLT, to reduce systematic errors and boost statistical significance.
Key open problems
The study touches on the problem of formation and evolution of planetary systems, specifically the question of what fraction of planets ultimately fall into their stars. It also relates to the mystery of the anomalous chemical composition of the Sun (refractory element deficiency) and the search for explanations within nucleosynthesis and the dynamical history of our system.
The knowledge machine's view
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
This study examines chemical traces of planet ingestion in 113 solar analogs using Bayesian model comparison, including a well-mixed model. Three robust candidates are identified with ingested masses ranging from 7.5 to 33 Earth masses, yielding an event frequency of about 2.7%.
Where its strength is
The strength of the work lies in its rigorous Bayesian approach, which preserves multidimensional information about abundance patterns and allows the ingestion signal to be separated from the effects of galactic chemical evolution.
Where it could go next
- It might be interesting to compare the derived frequencies with predictions from dynamical evolution models of planetary systems, for example, with work on the galactic ancestry of planets, to understand which system architectures more often lead to ingestion.based on: The Stellar Family Tree of Planets arXiv:2608.07331v1
- A related avenue is using chemical data to reconstruct star formation history; one could adapt this approach to account for the contribution of ingested planets to the chemical evolution of the galaxy and check whether this changes nucleosynthesis estimates.based on: Galactic Recipe: How the Sun Stopped Being Special arXiv:2607.01699v1
- It may be worth expanding the sample to stars with known planets to directly link ingestion frequency with system parameters, using approaches from the work on the galactic family tree.based on: The Galactic Family Tree: How Star Chemistry Tells the Story arXiv:2604.11974
Worth trying
- Apply the Bayesian framework to stars with confirmed planets and look for a correlation between the presence of hot Jupiters and ingestion signatures.
- Test how the choice of reference composition for the ingested material (Earth vs. CM chondrites) affects mass estimates, and develop models for intermediate compositions.
- Use lithium and beryllium data as additional indicators of mixing depth and event timing.
Why this may matter
This could help link the observed ingestion frequency to theories of planet formation and migration, clarifying how common catastrophic events are in planetary systems like our own.
Nearby works in our archive
- Galactic Recipe: How the Sun Stopped Being Specialsimilarity 0.69
- The Galactic Family Tree: How Star Chemistry Tells the Storysimilarity 0.60
- Tiny Twin Stars: When Ultradense Matter Breaks the Moldsimilarity 0.59
- Dance of the Invisible Giants: Gaia Finds a 'Desert' of Brown Dwarfssimilarity 0.59
- Interstellar Visitor Slims Down Before Our Eyessimilarity 0.59
- How Scars on the Disk Reveal a Galaxy's Pastsimilarity 0.59
- The Stellar Family Tree of Planetssimilarity 0.59
The closest work in the archive sits at 0.69 by meaning — the usual level for our corpus.
Original abstract
as written by the authors arXiv:2607.03504
We present a systematic Bayesian search for chemical fingerprints of planet engulfment in 113 solar twins and analogs with high-precision abundance measurements, 45 of which host known or candidate planets or brown-dwarf companions. We constructed a Bayesian framework with three sets of abundance models: random scatter, Galactic chemical evolution, and planet engulfment with bulk Earth or CM chondrite compositions. Through model comparisons, we identified three candidates whose abundance patterns strongly favor planet engulfment over the alternatives, with inferred engulfed masses of about 7.5-33 Earth masses. Our findings correspond to a nominal detection rate of 1-3% for planet-engulfment signatures among solar analogs. This work extends abundance-based engulfment searches beyond the binary-star context and provides a framework for probing star-planet co-evolution with solar analogs, which goes beyond the commonly used abundance-condensation-temperature correlation (Tc slope).
If the Sun swallowed the 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 events were more massive.
In Stanisław Lem's novel 'Solaris,' a sentient ocean consumes humans, but on a cosmic scale, entire planets become meals for their suns, leaving behind only spectral fingerprints — chemical memories of perished worlds.
Key numbers
- number of stars in the sample: 113
- number of stars with planets or candidates: 45
- number of robust engulfment candidates: 3
- masses of accreted material (M⊕): 7.5, 16, 33
- raw detection rate of signatures: 1–3%