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Formation of rocky super-earths from a narrow ring of planetesimals

Batygin, Konstantin and Morbidelli, Alessandro (2023) Formation of rocky super-earths from a narrow ring of planetesimals. Nature Astronomy, 7 . pp. 330-338. ISSN 2397-3366. doi:10.1038/s41550-022-01850-5.

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The formation of super-Earths, the most abundant planets in the Galaxy, remains elusive. These planets have masses that typically exceed that of the Earth by a factor of a few, appear to be predominantly rocky, although often surrounded by H/He atmospheres, and frequently occur in multiples. Moreover, planets that encircle the same star tend to have similar masses and radii, whereas those belonging to different systems exhibit remarkable overall diversity. Here we advance a theoretical picture for rocky planet formation that satisfies the aforementioned constraints: building upon recent work, which has demonstrated that planetesimals can form rapidly at discrete locations in the disk, we propose that super-Earths originate inside rings of silicate-rich planetesimals at approximately ~1 au. Within the context of this picture, we show that planets grow primarily through pairwise collisions among rocky planetesimals until they achieve terminal masses that are regulated by isolation and orbital migration. We quantify our model with numerical simulations and demonstrate that our synthetic planetary systems bear a close resemblance to compact, multi-resonant progenitors of the observed population of short-period extrasolar planets.

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Batygin, Konstantin0000-0002-7094-7908
Morbidelli, Alessandro0000-0001-8476-7687
Additional Information:K.B. is grateful to Caltech, Observatoire de la Côte d’Azur, the David and Lucile Packard Foundation and the National Science Foundation (grant number: AST 2109276) for their generous support. A.M. is grateful for support from the ERC advanced grant HolyEarth N. 101019380. Contributions. K.B. and A.M. jointly conceived the project and collaborated on the interpretation of the results. K.B. carried out the N-body simulations and led the writing of the paper. A.M. ran particle-in-a-box simulations and contributed to writing the manuscript. Data availability. Ascii output files summarizing the time series of our reference simulation (with an output interval of 1,000 years, totalling 1,010 files) are provided at Code availability. This work utilizes the publicly available mercury6 code ( The subroutine detailing user-defined forces is available on request from the corresponding author (K.B.). The authors declare no competing interests.
Group:Division of Geological and Planetary Sciences
Funding AgencyGrant Number
Observatoire de la Côte d’AzurUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
European Research Council (ERC)101019380
Record Number:CaltechAUTHORS:20230215-641165000.1
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:119287
Deposited By: George Porter
Deposited On:15 Feb 2023 18:43
Last Modified:03 May 2023 01:01

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