Heavy-metal Jupiters by major mergers: Metallicity versus mass for giant planets

Sivan Ginzburg*, Eugene Chiang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Some Jupiter-mass exoplanets contain of metals, well above the typically needed in a solid core to trigger giant planet formation by runaway gas accretion. We demonstrate that such 'heavy-metal Jupiters' can result from planetary mergers near ∼10 au. Multiple cores accreting gas at runaway rates gravitationally perturb one another on to crossing orbits such that the average merger rate equals the gas accretion rate. Concurrent mergers and gas accretion implies the core mass scales with the total planet mass as Mcore M1/5 - heavier planets harbour heavier cores, in agreement with the observed relation between total mass and metal mass. While the average gas giant merges about once to double its core, others may merge multiple times, as merger trees grow chaotically. We show that the dispersion of outcomes inherent in mergers can reproduce the large scatter in observed planet metallicities, assuming pre-runaway cores. Mergers potentially correlate metallicity, eccentricity, and spin.

Original languageAmerican English
Pages (from-to)680-688
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - 1 Oct 2020
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.


  • planets and satellites: composition
  • planets and satellites: dynamical evolution and stability
  • planets and satellites: formation
  • planets and satellites: gaseous planets


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