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Separating gas-giant and ice-giant planets by halting pebble accretion

Lambrechts, Michiel LU ; Johansen, Anders LU and Morbidelli, A. (2014) In Astronomy & Astrophysics 572.
Abstract
In the solar system giant planets come in two flavours: gas giants (Jupiter and Saturn) with massive gas envelopes, and ice giants (Uranus and Neptune) with much thinner envelopes around their cores. It is poorly understood how these two classes of planets formed. High solid accretion rates, necessary to form the cores of giant planets within the life-time of protoplanetary discs, heat the envelope and prevent rapid gas contraction onto the core, unless accretion is halted. We find that, in fact, accretion of pebbles (similar to cm sized particles) is self-limiting: when a core becomes massive enough it carves a gap in the pebble disc. This halt in pebble accretion subsequently triggers the rapid collapse of the super-critical gas... (More)
In the solar system giant planets come in two flavours: gas giants (Jupiter and Saturn) with massive gas envelopes, and ice giants (Uranus and Neptune) with much thinner envelopes around their cores. It is poorly understood how these two classes of planets formed. High solid accretion rates, necessary to form the cores of giant planets within the life-time of protoplanetary discs, heat the envelope and prevent rapid gas contraction onto the core, unless accretion is halted. We find that, in fact, accretion of pebbles (similar to cm sized particles) is self-limiting: when a core becomes massive enough it carves a gap in the pebble disc. This halt in pebble accretion subsequently triggers the rapid collapse of the super-critical gas envelope. Unlike gas giants, ice giants do not reach this threshold mass and can only bind low-mass envelopes that are highly enriched by water vapour from sublimated icy pebbles. This offers an explanation for the compositional difference between gas giants and ice giants in the solar system. Furthermore, unlike planetesimal-driven accretion scenarios, our model allows core formation and envelope attraction within disc life-times, provided that solids in protoplanetary discs are predominantly made up of pebbles. Our results imply that the outer regions of planetary systems, where the mass required to halt pebble accretion is large, are dominated by ice giants and that gas-giant exoplanets in wide orbits are enriched by more than 50 Earth masses of solids. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
planets and satellites: formation, planets and satellites: gaseous, planets, planets and satellites: composition, planets and satellites:, interiors, protoplanetary disks
in
Astronomy & Astrophysics
volume
572
publisher
EDP Sciences
external identifiers
  • wos:000346101700051
  • scopus:84912114725
ISSN
0004-6361
DOI
10.1051/0004-6361/201423814
language
English
LU publication?
yes
id
48dceee3-0ca1-46e1-bc13-3c8963753113 (old id 4944619)
date added to LUP
2015-01-28 11:52:57
date last changed
2017-11-12 03:41:03
@article{48dceee3-0ca1-46e1-bc13-3c8963753113,
  abstract     = {In the solar system giant planets come in two flavours: gas giants (Jupiter and Saturn) with massive gas envelopes, and ice giants (Uranus and Neptune) with much thinner envelopes around their cores. It is poorly understood how these two classes of planets formed. High solid accretion rates, necessary to form the cores of giant planets within the life-time of protoplanetary discs, heat the envelope and prevent rapid gas contraction onto the core, unless accretion is halted. We find that, in fact, accretion of pebbles (similar to cm sized particles) is self-limiting: when a core becomes massive enough it carves a gap in the pebble disc. This halt in pebble accretion subsequently triggers the rapid collapse of the super-critical gas envelope. Unlike gas giants, ice giants do not reach this threshold mass and can only bind low-mass envelopes that are highly enriched by water vapour from sublimated icy pebbles. This offers an explanation for the compositional difference between gas giants and ice giants in the solar system. Furthermore, unlike planetesimal-driven accretion scenarios, our model allows core formation and envelope attraction within disc life-times, provided that solids in protoplanetary discs are predominantly made up of pebbles. Our results imply that the outer regions of planetary systems, where the mass required to halt pebble accretion is large, are dominated by ice giants and that gas-giant exoplanets in wide orbits are enriched by more than 50 Earth masses of solids.},
  articleno    = {A35},
  author       = {Lambrechts, Michiel and Johansen, Anders and Morbidelli, A.},
  issn         = {0004-6361},
  keyword      = {planets and satellites: formation,planets and satellites: gaseous,planets,planets and satellites: composition,planets and satellites:,interiors,protoplanetary disks},
  language     = {eng},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {Separating gas-giant and ice-giant planets by halting pebble accretion},
  url          = {http://dx.doi.org/10.1051/0004-6361/201423814},
  volume       = {572},
  year         = {2014},
}