Enhanced collisional growth to a protoplanet that has an atmosphere

S. Inaba*, M. Ikoma

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

117 Citations (Scopus)


Once a protoplanet becomes larger than about lunar size, it accumulates a significant atmosphere that surrounds the solid core. When a planetesimal approaches the protoplanet, it interacts with the atmosphere. If enough energy of the planetesimal is lost by gas drag of the atmosphere, it is captured in the atmosphere even if its original trajectory would not lead to a direct collision with the solid core of the protoplanet. This increases the collision rate, resulting in faster growth of the protoplanet. We have derived the analytical calculations for the collision rate, and calculated the structure of the atmosphere and the trajectories of the planetesimals in the atmosphere. As a result of their large gas drag, small planetesimals are easily captured, resulting in a large rate of collision with the protoplanet. A collision rate of a protoplanet of Earth size with a planetesimal of 100 m radius is, for example, enhanced by a factor of ∼10. These effects play an essential role in the study of formation of solid cores of gas giant planets by the core accretion model.

Original languageEnglish
Pages (from-to)711-723
Number of pages13
JournalAstronomy and Astrophysics
Issue number2
Publication statusPublished - 2003 Nov
Externally publishedYes


  • Solar system: formation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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