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Image: A. Angelich (NRAO/AUI/NSF)/ALMA (ESO/NAOJ/NRAO)
Thebehaviourofpebblesaroundthesnowlineinprotoplanetarydisks
University of AmsterdamDjoekeSchoonenberg
SPF2, Biosphere, 15 March 2018
withChrisOrmel,BeibeiLiu,SebastiaanKrijt
Water snowline around V883 Ori
Cieza et al., Nature, 535, 2016 Schoonenberg, Okuzumi, & Ormel, A&A, 605, L2 (2017)
Outline• Planetesimalformationbystreaminginstabilityaroundthesnowline
• FormationoftheTRAPPIST-1planets
Streaminginstability• Mechanismtodirectlyformplanetesimalsfrompebbles
• Requireslocalsolids-to-gasratiooforderunity
Johansen,Youdin,&MacLow2009(seealsoYoudin&Goodman2005;Johansen,Henning,&Klahr2006;
Johansen&Youdin2007;Simonetal.2016;Yangetal.2017)
Krijtetal.2016(seealsoBirnstieletal.2012,Lambrechts&Johansen2014)
Schoonenberg&Ormel,A&A,602,A21(2017)
Planetesimalformationoutsidethesnowline:alocaltransportmodel
constantmassfluxoficypebbles
snowline
↵ = 3 · 10�3
⌧ = 3 · 10�2
Mgas = 10�8M�yr�1
Mpeb/Mgas = 0.8
e-foldingtimescale≈(rpeak-rsnow)/vgas
Schoonenberg&Ormel,A&A,602,A21(2017)
↵ = 3 · 10�3
⌧ = 3 · 10�2
Mgas = 10�8M�yr�1
Mpeb/Mgas = 0.8
Schoonenberg&Ormel,A&A,602,A21(2017)‘dirt’‘freesilicates’
Many-seedsmodelenhances‘bump’andleadstoplanetesimalicefractionof~0.5
WaterfractionofTRAPPIST-1planetsdictatedbyratiooficypebbleaccretiontowater-poorpebbleaccretion
Ormel,Liu,andSchoonenberg,A&A,604,A1(2017)
�18
Planetesimalmergersandmigration
UsingMERCURY(Chambers1999)
firstplanetaryembryohascrossedsnowline
• PlanetesimalformationinourTRAPPIST-1modelstartsafterafew10^3years
• Firstplanetembryomigratesacrossthesnowlineafterafew10^4years
• Withoutmigration,planetesimalformationisaself-limitingprocess(becausepebblefluxgoesdownduetopebbleaccretionasplanetesimalmassgrows)
• Icypebbleaccretionversusrockypebbleaccretionaftericeline-crossingdeterminesbulkcompositionofTRAPPIST-1planets
• PRELIMINARY:waterfractionsofafewpercentseemtobefeasible
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