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

Fromdusttoplanets

Nottoscale!(noteventolog-scale)

µm

km

dust

planetesimal

planet

1e3km

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)

Icypebbledesigns

‘single-seed’

‘many-seeds’

evaporationfront

Icypebbledesigns

MichaelHammer,Astrobites

‘single-seed’

‘many-seeds’

evaporationfront

↵ = 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

FormationscenariofortheTRAPPIST-1planets

Ormel,Liu,andSchoonenberg,A&A,604,A1(2017)

Grimmetal.,A&A,inpress

Jack Cook/WHOI/USGS

WaterfractionofTRAPPIST-1planetsdictatedbyratiooficypebbleaccretiontowater-poorpebbleaccretion

Ormel,Liu,andSchoonenberg,A&A,604,A1(2017)

planetesimalformation+pebbleaccretion (nomigration/planetesimalmergers)

�16

Planetesimalmergersandmigration

UsingMERCURY(Chambers1999)

�17

Planetesimalmergersandmigration

UsingMERCURY(Chambers1999)

�18

Planetesimalmergersandmigration

UsingMERCURY(Chambers1999)

firstplanetaryembryohascrossedsnowline

↵ = 10�3

Mgas = 10�10M� yr�1

Z = 0.02

b c d e f g h

• PlanetesimalformationinourTRAPPIST-1modelstartsafterafew10^3years

• Firstplanetembryomigratesacrossthesnowlineafterafew10^4years

• Withoutmigration,planetesimalformationisaself-limitingprocess(becausepebblefluxgoesdownduetopebbleaccretionasplanetesimalmassgrows)

• Icypebbleaccretionversusrockypebbleaccretionaftericeline-crossingdeterminesbulkcompositionofTRAPPIST-1planets

• PRELIMINARY:waterfractionsofafewpercentseemtobefeasible

Takehomemessages