Advanced

The role of pebble fragmentation in planetesimal formation II. Numerical simulations

Jansson, Karl Wahlberg LU ; Johansen, Anders LU ; Syed, Mohtashim Bukhari and Blum, Jürgen (2017) In Astrophysical Journal 835(1).
Abstract

Some scenarios for planetesimal formation go through a phase of collapse of gravitationally bound clouds of millimeter- to centimeter-size pebbles. Such clouds can form, for example, through the streaming instability in protoplanetary disks. We model the collapse process with a statistical model to obtain the internal structure of planetesimals with solid radii between 10 and 1000 km. During the collapse, pebbles collide, and depending on their relative speeds, collisions have different outcomes. A mixture of particle sizes inside a planetesimal leads to better packing capabilities and higher densities. In this paper we apply results from new laboratory experiments of dust aggregate collisions (presented in a companion paper) to model... (More)

Some scenarios for planetesimal formation go through a phase of collapse of gravitationally bound clouds of millimeter- to centimeter-size pebbles. Such clouds can form, for example, through the streaming instability in protoplanetary disks. We model the collapse process with a statistical model to obtain the internal structure of planetesimals with solid radii between 10 and 1000 km. During the collapse, pebbles collide, and depending on their relative speeds, collisions have different outcomes. A mixture of particle sizes inside a planetesimal leads to better packing capabilities and higher densities. In this paper we apply results from new laboratory experiments of dust aggregate collisions (presented in a companion paper) to model collision outcomes. We find that the internal structure of a planetesimal is strongly dependent on both its mass and the applied fragmentation model. Low-mass planetesimals have no/few fragmenting pebble collisions in the collapse phase and end up as porous pebble piles. The number of fragmenting collisions increases with increasing cloud mass, resulting in wider particle size distributions and higher density. The collapse is nevertheless "cold" in the sense that collision speeds are damped by the high collision frequency. This ensures that a significant fraction of large pebbles survive the collapse in all but the most massive clouds. Our results are in broad agreement with the observed increase in density of Kuiper Belt objects with increasing size, as exemplified by the recent characterization of the highly porous comet 67P/Churyumov-Gerasimenko.

(Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
methods: analytical, methods: numerical, planets and satellites: formation
in
Astrophysical Journal
volume
835
issue
1
publisher
University of Chicago Press
external identifiers
  • scopus:85011277265
  • wos:000393455400109
ISSN
0004-637X
DOI
10.3847/1538-4357/835/1/109
language
English
LU publication?
yes
id
f30244e9-4d90-4a9c-a4fb-ca9afda5c5c9
date added to LUP
2017-02-15 08:20:53
date last changed
2018-03-25 04:34:08
@article{f30244e9-4d90-4a9c-a4fb-ca9afda5c5c9,
  abstract     = {<p>Some scenarios for planetesimal formation go through a phase of collapse of gravitationally bound clouds of millimeter- to centimeter-size pebbles. Such clouds can form, for example, through the streaming instability in protoplanetary disks. We model the collapse process with a statistical model to obtain the internal structure of planetesimals with solid radii between 10 and 1000 km. During the collapse, pebbles collide, and depending on their relative speeds, collisions have different outcomes. A mixture of particle sizes inside a planetesimal leads to better packing capabilities and higher densities. In this paper we apply results from new laboratory experiments of dust aggregate collisions (presented in a companion paper) to model collision outcomes. We find that the internal structure of a planetesimal is strongly dependent on both its mass and the applied fragmentation model. Low-mass planetesimals have no/few fragmenting pebble collisions in the collapse phase and end up as porous pebble piles. The number of fragmenting collisions increases with increasing cloud mass, resulting in wider particle size distributions and higher density. The collapse is nevertheless "cold" in the sense that collision speeds are damped by the high collision frequency. This ensures that a significant fraction of large pebbles survive the collapse in all but the most massive clouds. Our results are in broad agreement with the observed increase in density of Kuiper Belt objects with increasing size, as exemplified by the recent characterization of the highly porous comet 67P/Churyumov-Gerasimenko.</p>},
  articleno    = {109},
  author       = {Jansson, Karl Wahlberg and Johansen, Anders and Syed, Mohtashim Bukhari and Blum, Jürgen},
  issn         = {0004-637X},
  keyword      = {methods: analytical,methods: numerical,planets and satellites: formation},
  language     = {eng},
  month        = {01},
  number       = {1},
  publisher    = {University of Chicago Press},
  series       = {Astrophysical Journal},
  title        = {The role of pebble fragmentation in planetesimal formation II. Numerical simulations},
  url          = {http://dx.doi.org/10.3847/1538-4357/835/1/109},
  volume       = {835},
  year         = {2017},
}