2005/08/30 by Andrew N. Youdin, Youdin, Andrew N.
Physics and Astronomy · #Astro and Planetary Science #Astrophysics (astro-ph) #Astrophysics and Star Formation Studies #FOS: Physical sciences #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0508662
9 pages, 8 figures, submitted to ApJ
arxiv created 2005/08/30 · openalex publication_date 2005/08/30 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We show that small solids in low mass, turbulent protoplanetary disks collect\ninto self-gravitating rings. Growth is faster than disk lifetimes and radial\ndrift times for moderately strong turbulence, characterized by dimensionless\ndiffusivities, \αg < 10-6 -- 10-3 when particles are mm-sized.\nThis range reflects a strong dependance on disk models. Growth is faster for\nhigher particle surface densities. Lower gas densities and larger solids also\ngive faster growth, as long as aerodynamic coupling is tight. In simple power\nlaw models, growth is slowest around ~0.3 AU, where drag coupling is strongest\nfor mm-sized solids. Growth is much faster close to the star where orbital\ntimes are short, with implications for in situ formation of short period\nextrasolar planets. Growth times also decrease toward the outer disk where\nlower gas densities allow greater particle settling. Beyond roughly Kuiper Belt\ndistances however, solids are sufficiently decoupled from gas that dissipative\ngravitational instabilities are less effective. Turbulence not only slows\ngrowth, but also increases radial wavelengths. The initial solid mass in an\nunstable ring can be ~0.01 MEarth or greater, huge compared to km-sized\nplanetesimals. Nonlinear fragmentation, which has not been studied in detail,\nwill lower the final planetesimal mass. We consider applications to the\nasteroid belt and discuss the alternate hypothesis of collisional\nagglomeration.\n