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Formation and composition ofsuper-Earths
Bertram Bitsch
Bertram Bitsch (MPIA) Architecture and composition of planetary
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Formation of planetary systems by pebble accretion
Bertram Bitsch (MPIA) Architecture and composition of planetary
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Observational constraints
super Earths
cold Jupitershot Jupiters
(Winn & Fabrycky, 2015)
Super-Earth: Size: 1− 4RE (1ME
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Observational constraints
super Earths
cold Jupitershot Jupiters
(Winn & Fabrycky, 2015)
Super-Earth: Size: 1− 4RE (1ME
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Formation ingredients: migration and pebble accretion
Planets interact gravitationally with the gas disc and
migrate
⇒ Outward migration close to the water ice line (high ν
needed!)(Bitsch et al. 2013, 2014, 2015a)
Planets can accrete pebbles very efficiently
⇒ Planet growth stops at the pebble isolation mass(Lambrechts et
al. 2014; Bitsch et al. 2018, Ataiee et al. 2018)
Bertram Bitsch (MPIA) Architecture and composition of planetary
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Super-Earth systems
(Izidoro, Bitsch, et al., 2019)
Bertram Bitsch (MPIA) Architecture and composition of planetary
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Matching observations of super-Earth systems
(Izidoro, Bitsch, et al. 2019)
Mixture between stable systems (5%) and unstable systems
(95%)
⇒ Matches observations very well! (see also Izidoro, et al.
2017)Bertram Bitsch (MPIA) Architecture and composition of
planetary systems 6 / 9
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Composition of planets in our simulations
(Izidoro, Bitsch, et al. 2019)
super-Earths are mostly wet in our simulations!
⇒ How to make them rocky? (without invoking other meachanisms,
see talk by T. Lichtenberg)
Bertram Bitsch (MPIA) Architecture and composition of planetary
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Planet migration to change the water content
0.01
0.1
1
10
0.1 1
M [M
E]
r [AU]
water ice lineoutward
only inward
0.01
0.1
1
10
0.1 1 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
wat
er ic
e fr
actio
n
(Bitsch et al. 2019b)
Outward migration connected to the water ice line (e.g. Bitsch
et al. 2013, 2015a)
Planets formed at the water ice line that experience
outwardmigration will accrete a larger water ice fraction
If planets instead migrate only inwards they can finish their
formationin the dry part and will have a lower water ice
fraction(see also Schoonenberg et al. 2019 for application to
Trappist-1)
⇒ Migration direction important for planetary composition,
especially ofplanets formed close to ice lines!
Bertram Bitsch (MPIA) Architecture and composition of planetary
systems 8 / 9
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Planet migration to change the water content
0.01
0.1
1
10
0.1 1
M [M
E]
r [AU]
water ice lineoutward
only inward
0.01
0.1
1
10
0.1 1 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
wat
er ic
e fr
actio
n
(Bitsch et al. 2019b)
Outward migration connected to the water ice line (e.g. Bitsch
et al. 2013, 2015a)
Planets formed at the water ice line that experience
outwardmigration will accrete a larger water ice fraction
If planets instead migrate only inwards they can finish their
formationin the dry part and will have a lower water ice
fraction(see also Schoonenberg et al. 2019 for application to
Trappist-1)
⇒ Migration direction important for planetary composition,
especially ofplanets formed close to ice lines!
Bertram Bitsch (MPIA) Architecture and composition of planetary
systems 8 / 9
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SummaryFormation of super-Earths:
Interplay between accretion, migration, disc evolution and
instabilities!
Capture in resonant chains through type-I migration at inner
disc edge
⇒ Breaking of resonant chains by instabilities(Izidoro et al.
2017, 2019; Lambrechts et al. 2019)
⇒ Mixture between stable and unstable systems leads to very
goodmatch to Kepler observations!
Water content of super-Earths:
Formation completed exterior to the water ice line: water
rich
Formation completed interior to the water ice line: water
poor
⇒ Direction of migration determines the water ice content
ofsuper-Earths formed close to the water ice line (Bitsch et al.
2019b)
Bertram Bitsch (MPIA) Architecture and composition of planetary
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