From Dust To Planetesimal: The Snowball Phase ?

Abstract

The standard model of planet formation considers an initial phase in which planetesimals form from a dust disk, followed by a phase of mutual planetesimal-planetesimal collisions, leading eventually to the formation of planetary embryos. However, there is a potential transition phase (which we call the "snowball phase"), between the formation of the first planetesimals and the onset of mutual collisions amongst them, which has often been either ignored or underestimated in previous studies. In this snowball phase, isolated planetesimals move on Keplerian orbits and grow solely via the direct accretion of sub-cm sized dust entrained with the gas in the protoplanetary disk. Using a simplified model in which planetesimals are progressively produced from the dust, we consider the expected sizes to which the planetesimals can grow before mutual collisions commence and derive the dependence of this size on a number of critical parameters, including the degree of disk turbulence, the planetesimal size at birth and the rate of planetesimal creation. For systems in which turbulence is weak and the planetesimals are created at a low rate and with relatively small birth size, we show that the snowball growth phase can be very important, allowing planetesimals to grow by a factor of 10^6 in mass before mutual collisions take over. In such cases, the snowball growth phase can be the dominant mode to transfer mass from the dust to planetesimals. Moreover, such growth can take place within the typical lifetime of a protoplanetary gas disk. A noteworthy result is that ... ...(see the paper). For the specific case of close binaries such as Alpha Centauri ... ... (see the paper). From a more general perspective, these preliminary results suggest that an efficient snowball growth phase provides a large amount of "room at the bottom" for theories of planet formation.

Accepted for publication in the Astrophysical Journal. 15 pages, 4 figures, 1 table

References in corpus (12)

• Towards planetesimals: dense chondrule clumps in the protoplanetary nebula
• Planetesimal formation around the snow line in MRI-driven turbulent protoplanetary disks
• Towards Initial Mass Functions for Asteroids and Kuiper Belt Objects
• Relative velocities among accreting planetesimals in binary systems: the circumprimary case
• High Velocity Dust Collisions: Forming Planetesimals in a Fragmentation Cascade with Final Accretion
• Planetesimal and gas dynamics in binaries
• iVINE - Ionization in the parallel tree/SPH code VINE: First results on the observed age-spread around O-stars
• Planet formation in Alpha Centauri A revisited: not so accretion-friendly after all
• Planetesimal Accretion in Binary Systems: Could Planets Form Around Alpha Centauri B ?
• Planetesimal collisions in binary systems
• A coagulation-fragmentation model for the turbulent growth and destruction of preplanetesimals
• Planetesimal Accretion in Binary Systems: The Effects of Gas Dissipation

Cited by in corpus (21)

• A Major Asymmetric Dust Trap in a Transition Disk
• Planetesimal formation by sweep-up: How the bouncing barrier can be beneficial to growth
• How not to build Tatooine: the difficulty of in situ formation of circumbinary planets Kepler 16b, Kepler 34b and Kepler 35b
• Against all odds? Forming the planet of the HD196885 binary
• Understanding how planets become massive. I. Description and validation of a new toy model
• The fate of planetesimals in turbulent disks with dead zones. II. Limits on the viability of runaway accretion
• The Heavy Element Composition of Disk Instability Planets Can Range From Sub- to Super-Nebular
• Planetesimal formation via sweep-up growth at the inner edge of dead zones
• A Tale of Planet Formation: From Dust to Planets
• Planet formation in Binaries
• Influence of the circumbinary disk gravity on planetesimal accumulation in the Kepler 16 system
• Planets in Binaries: Formation and Dynamical Evolution
• Planet Formation In Highly Inclined Binary Systems I. Planetesimals Jump Inwards And Pile Up
• On dust evolution in planet-forming discs in binary systems. I -- Theoretical and numerical modelling: radial drift is faster in binary discs
• On the dynamics and collisional growth of planetesimals in misaligned binary systems
• Planetesimal Dynamics in Inclined Binary Systems: The Role of Gas-Disk Gravity
• Planet seeding through gas-assisted capture of interstellar objects
• Forming Different Planetary Systems
• Interstellar planetesimals: potential seeds for planet formation?
• Planet Formation in Highly Inclined Binary Systems. II. Orbital Alignment or Anti-alignment and Planet Growth Boost in Intermediate Separation Binaries
• A quantification of hydrodynamical effects on protoplanetary dust growth