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Chemical evidence for planetary ingestion in a quarter of Sun-like stars


Stellar members of binary systems are formed from the same material, and therefore they should be chemically identical. However, recent studies have unveiled chemical differences between the two members of binary pairs composed of Sun-like stars. These chemically inhomogeneous binaries represent one of the most contradictory examples in stellar astrophysics and a source of tension between theory and observations. It is still unclear whether the abundance variations are the result of inhomogeneities in the protostellar gas clouds or are due to planet engulfment events that occurred after the stellar formation. The former scenario undermines the general belief that the chemical makeup of stars provides the fossil information of the environment in which they formed, whereas the second scenario would shed light on the possible evolutionary paths of planetary systems. Our study provides compelling evidence in favour of the planet engulfment scenario. We also establish that planet engulfment events occur in Sun-like stars with a 20–35% probability. Therefore, an important fraction of planetary systems undergo very dynamical evolutionary paths that critically modify their architectures, unlike our calm Solar System. This study opens the possibility of using chemical abundances of stars to identify which ones are the most likely to host Solar System analogues.

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Fig. 1: The frequency of chemically anomalous pairs.
Fig. 2: The [Fe/C] percentile ranks.
Fig. 3: The ΔFe–ΔLi diagram.

Data availability

All data generated or analysed during this study are included in this published article as Supplementary Data files.


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This work has made use of observations collected at the ESO (programmes 188.C-0265, 0103.C-0785 and 0101.C-0275) and of data from the European Space Agency mission Gaia. We are grateful to K. Hawkins, and F. Liu for having shared with us tabular and spectroscopic data. L.S. thanks A. I. Karakas for her support and advice. L.S. also acknowledges financial support from the Australian Research Council (Discovery Project 170100521) and continuing support from the Italian Space Agency through contract 2018-24-HH.0 to the National Institute for Astrophysics (INAF). J.M. thanks FAPESP (2018/04055-8). A.R.C. is supported in part by the Australian Research Council through a Discovery Early Career Researcher Award (DE190100656). M.C. is supported by MIUR under PRIN programme 2017Z2HSMF. Parts of this research were supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013.

Author information




All authors assisted in the development, analysis and writing of the paper. L.S. led and played a part in all aspects of the analysis, and wrote the manuscript. P.S. carried out the spectroscopic analysis of the HARPS sample. J.M. and M.B. contributed in designing this study and in the interpretations of the results. A.R.C. identified the binary pairs with HARPS spectra in the ESO archive and provided the cross-match to the Gaia data set. M.C. and E.F. derived the Li abundances. A.V. contributed to the discussion of the results.

Corresponding author

Correspondence to Lorenzo Spina.

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The authors declare no competing interests.

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Peer review information Nature Astronomy thanks Melinda Soares-Furtado and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary information

Supplementary Figs. 1 and 2, Tables 1–3 and references.

Supplementary Data 1

Full sample of binary pairs. Columns: • Star1 and Star2: name of the two stellar components of the binary system. • teff_ave: average of the Teff derived for the two stars of the binary pair. Unit: Kelvin. • diff_feh: [Fe/H] difference within the pair. • err_diff_feh: uncertainty associated with diff_feh. • Source: reference from which data have been taken.

Supplementary Data 2

HARPS sample. Atmospheric and astrometric parameters. Columns: • Star: name of the star. • RA, DEC: J2000 right ascension and declination. Unit: degrees. • teff, err_teff: Teff and its uncertainty. Unit: Kelvin. • logg, err_logg: logarithm of the surface gravity and its uncertainty. • feh, err_feh: [Fe/H] and its uncertainty. • vt, err_vt: microturbulence and its uncertainty. Unit: km s−1. • Gaia ID, plx, err_plx, pmra, err_pmra, pmdec, err_pmdec: Gaia source_id, astrometric solution and their uncertainties taken from Gaia DR2. Units: parallax is in mas, proper motions in mas yr−1.

Supplementary Data 3

HARPS sample. Chemical abundances relative to the Sun. Columns: • id: name of the star. • [X], err_X, n_[X]: abundance [X/H] relative to the X element, its uncertainty, and number of absorption lines used for the analysis.

Supplementary Data 4

HARPS sample. Differential abundances within the pair. Columns: • star1, star2: name of the two binary components. • [X], err_X, n_[X]: differential abundance [X/H] relative to the X element within the pair, its uncertainty, and number of absorption lines used for the analysis.

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Spina, L., Sharma, P., Meléndez, J. et al. Chemical evidence for planetary ingestion in a quarter of Sun-like stars. Nat Astron (2021).

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