The Formation of Planetesimals

Journal Article · Wed Aug 01 04:00:00 EDT 1973 · Astrophysical Journal

DOI:https://doi.org/10.1086/152291· OSTI ID:4304993

Goldreich, Peter; Ward, William R.

Four stages in the accretion of planetesimals are described. The initial stage is the condensation of dust particles from the gaseous solar nebula as it cools. These dust particles settle into a thin disk which is gravitationally unstable. A first generation of planetesimals, whose radii range up to approximates 10^-1 km, form from the dust disk by direct gravitational collapse to solid densities on a time scale of the order of 1 year. The resulting disk, composed of first-generation planetesimals, is still gravitationally unstable, and the planetesimals are grouped into clusters containing approximately 10⁴ members. The contraction of these clusters is controlled by the rate at which gas drag damps their internal rotational and random kinetic energies. On a time scale of a few thousand years, the clusters contract to form a second generation of planetesimals having radii of the order of 5 km. Further coalescence of planetesimals proceeds by direct collisions which seem capable of producing growth at a rate of the order of 15 cm per year at 1 AU. The final stage of accretion during which planet-sized objects form is not considered here.

• Research Organization: California Inst. of Tech., Pasadena
• Sponsoring Organization: USDOE
• NSA Number: NSA-29-024979
• OSTI ID: 4304993
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Vol. 183; ISSN 0004-637X
• Publisher: Institute of Physics (IOP)
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

*PLANET-SYSTEM ACCRETION-- TIME DEPENDENCE
*SOLAR SYSTEM-- PLANET- SYSTEM ACCRETION
COLLISIONS
GRAVITATION
N56400* --Physics (Astrophysics & Cosmology)--Solar Phenomena
SIZE