Encyclopedia of Astrobiology

2015 Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James (Jim) CleavesII, Daniele L. Pinti, José Cernicharo Quintanilla, Daniel Rouan, Tilman Spohn, Stéphane Tirard, Michel Viso

Runaway Growth

  • Sean N. RaymondEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-3-662-44185-5_1397


Runaway growth is an accelerated phase in planetary growth during which the growth rate scales with the planet mass (dM/dt ∼ M4/3) such that the largest bodies get larger at a rapid and increasing rate. Runaway growth occurs in cases for which  gravitational focusing of small bodies (planetesimals) is very strong. The runaway growth phase is thought to be quite short in most situations and to be stopped when random velocities of the planetesimals are increased to the point where gravitational focusing is stopped and accretion returns to the geometrical regime (where the collision rate is simply proportional to a body’s surface area). However, in situations with very strong damping of planetesimal eccentricities (e.g., via  gas drag), runaway growth of  planetary embryos can be extended all the way to the point at which a growing planet becomes dynamically isolated from its neighbors by accreting all of the mass in its local neighborhood.

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© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  1. 1.Laboratoire d’Astrophysique de BordeauxCNRS, Universite de BordeauxBordeauxFrance