Formation and composition of super-Earthspeople.virginia.edu/~jct6e/FSTPII/talks/bitsch_b.pdf · (Bitsch et al. 2019b) Outward migration connected to the water ice line (e.g. Bitsch

Formation and composition ofsuper-Earths

Bertram Bitsch

Bertram Bitsch (MPIA) Architecture and composition of planetary systems 1 / 9

Formation of planetary systems by pebble accretion

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Observational constraints

super Earths

cold Jupitershot Jupiters

(Winn & Fabrycky, 2015)

Super-Earth: Size: 1− 4RE (1ME

Observational constraints

super Earths

cold Jupitershot Jupiters

(Winn & Fabrycky, 2015)

Super-Earth: Size: 1− 4RE (1ME

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)

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Super-Earth systems

(Izidoro, Bitsch, et al., 2019)

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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

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)

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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

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

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)

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