EVOLUTION OF PLANETARY SYSTEMS
Alessandro Morbidelli
CNRS/Obs. De la Cote d’Azur, Nice, France
With inputs from: B. Bitsch, C. Cossou, A. Izidoro, A. Johansen, M. Lambrechts, S. Raymond
The Big Questions
•
Dichotomy of the Solar System
(Mars-size planetary embryos in the inner
system, multi-Earth-mass cores in the outer system within ~ 3 My)
•
Hot Super –Earth: the most abundant category of planets
•
Why not here?
•
Why there are typically no giant planets in these Super-Earth systems?
•
Can we place the Solar System evolution in the broad context?
Bitsch et al., 2014
Migration vs. planetary mass in a realistic disk
Migr
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snowlinee dM/dt=10-8M sun/ySee Bitsch’s presentation on Thursday for H/r as a function of disk properties and time
Bitsch et al., 2014
Migration vs. planetary mass in a realistic disk
Migr
ation
ra
te
In
w
ar
d
O
utw
ar
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snowlinee dM/dt=10-8M sun/yBitsch et al., 2014
Migration vs. planetary mass in a realistic disk
Migr
ation
ra
te
In
w
ar
d
O
utw
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snowlinee dM/dt=10-8M sun/yHydro-dynamical simulations of a system of proto-planets, the innermost of which is retained on a non-migrating orbit Morbidelli et al., 2008 No-migration radius 8Me
The impact of Super-Earth migration on the local formation of terrestrial planets
(Izidoro, Morbidelli and Raymond, in press) Depends strongly on migration timescale
The impact of Super-Earth migration on the local formation of terrestrial planets
(Izidoro, Morbidelli and Raymond, in press) Depends strongly on migration timescale
The impact of Super-Earth migration on the local formation of terrestrial planets
(Izidoro, Morbidelli and Raymond, in press) Depends strongly on migration timescale
The impact of Super-Earth migration on the local formation of terrestrial planets
(Izidoro, Morbidelli and Raymond, in press) Depends strongly on migration timescale
Bitsch et al., 2014
Migration vs. planetary mass in a realistic disk
Migr
ation
ra
te
In
w
ar
d
O
utw
ar
d
snowlinee dM/dt=10-8M sun/yGiant planet in Type II regime
Observed radial distribution of giant planets (more massive than Saturn)
Courtesy of A. Crida It tacks!
Another possible solution valid for the Solar System (Jupiter + Saturn): The Grand Tack Masset and Snellgrove, 2001; Morbidelli and Crida, 2007; Pierens and Nelson, 2008; Walsh et al., 2011
Giant planets are extremely effective in retaining Super-Earths behind them
Giant planets are extremely effective in retaining Super-Earths behind them
The Big Questions
•
Dichotomy of the Solar System
(Mars-size planetary embryos in the inner
system, multi-Earth-mass cores in the outer system within ~ 3 My)
•
Hot Super –Earth: the most abundant category of planets
•
Why not here?
•
Why there are typically no giant planets in these Super-Earth systems?
The “egg” of outward migration is key to hold a core until it becomes massive
enough to form a giant planet.
If this happens to the innermost core, and the giant planet is retained from
migrating into the inner system (e.g. grand tack) in most cases all ice-giant
planets remain in the outer disk as in our Solar System.
Without Jupiter and Saturn, Uranus and Neptune would have migrated into the
inner Solar System
The density of solid material beyond the snowline is only a factor of 2 larger, insufficient to explain the difference
The Key is pebble accretion (Ormel and Klahr, 2010; Lambrechts and Johansen, 2012) Beyond the snowline, pebbles can be dm-size objects of ice and silicates (Ros and Johansen, 2013) Once pebbles drift inside the snowline, the ice sublimates and much smaller
(chondrule-sized?) silicate grains are released
Pebble accretion is thus much less efficient in the inner System
Dichotomy of the Solar System
(Mars-size planetary embryos in the inner system, multi-Earth-mass cores in the outer system within ~ 3 My). Why?Also, when proto-Jupiter reached a mass of ~ 20 Earth masses, it cut off the flow of pebbles towards the inner solar system
Lambrechts, Johansen and Morbidelli, submitted; Morbidelli and Nesvorny, 2012
If the growth of planetary embryos and cores occurs by pebble accretion (Lambrechts and Johansen, 2012), this explains why the inner Solar System starved in mass and could form only small planets.