Particle clumping and planetesimal formation depend strongly on metallicity

Anders Johansen, Andrew Youdin, Mordecai Mark Mac Low

Research output: Contribution to journalArticlepeer-review

295 Scopus citations


We present three-dimensional numerical simulations of particle clumping and planetesimal formation in protoplanetary disks with varying amounts of solid material. As centimeter-size pebbles settle to the mid-plane, turbulence develops through vertical shearing and streaming instabilities. We find that when the pebble-to-gas column density ratio is 0.01, corresponding roughly to solar metallicity, clumping is weak, so the pebble density rarely exceeds the gas density. Doubling the column density ratio leads to a dramatic increase in clumping, with characteristic particle densities more than 10 times the gas density and maximum densities reaching several thousand times the gas density. This is consistent with unstratified simulations of the streaming instability that show strong clumping in particle-dominated flows. The clumps readily contract gravitationally into interacting planetesimals on the order of 100km in radius. Our results suggest that the correlation between host star metallicity and exoplanets may reflect the early stages of planet formation. We further speculate that initially low-metallicity disks can be particle enriched during the gas dispersal phase, leading to a late burst of planetesimal formation.

Original languageEnglish (US)
Pages (from-to)L75-L79
JournalAstrophysical Journal
Issue number2 PART 2
StatePublished - 2009
Externally publishedYes


  • Diffusion
  • Hydrodynamics
  • Instabilities
  • Planetary systems: protoplanetary disks
  • Solar system: formation
  • Turbulence

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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