S. Jin, P. Mollière Max Planck Institut for Astronomy, Heidelberg, Germany Y. Alibert & W. Benz University of Bern, Switzerland Christoph Mordasini PLATO meeting Taormina 3.12.2014 Time: a new dimension of constraints for planet formation and evolution theory
Adding the temporal dimension with PLATO Rauer et al. 2013 Stellar masses and ages will be tightly constrained by the systematic use of asteroseismology. Ages will be known to % for solar-like stars. For the first time with PLATO: population-wide and accurate planet evolution in time as a measurable quantity on the observational side On the theoretical side: temporal evolution: a fundamental and omnipresent concept
Radius evolution and formation Radius evolution in time depends on Implication for planet formation initial thermodynamic state (how hot initially / entropy) Bulk composition (H/He, silicates, Fe, ices) Energy transport in the interior (convection) Atmosphere & opacity (Giant) planet formation mode, gas accretion shock structure Formation location, migration, opacity in the protoatmosphere, planetesimal / pebble accretion Accretion history, planetesimal size Enrichment, formation location Atmospheric escape/evaporation Efficiency of H/He accretion Bloating mechanisms Migration mechanism (Kozai, disk migration) New constraints to better understand planet formation
Temporal evolution: giant planets Fortney et al. 2011 Atmospheric model Inflation Guillot & Showman 2002 Leconte & Chabrier 2013 Energy transport Composition Init. cond. Mordasini 2013
Temporal evolution low-mass planet Mini-Neptune a=0.05 AU Mcore=4 MEarth Menv=0.1 MEarth Linit=0.1 LJ Earth-like core (0.33 iron, 0.66 silicate) X-rays & EUV evaporation Solar-composition opacity Radius [Earth radii] 7 6 5 4 3 2 total radius w/o evap total radius w/ evap core radius Envelope Mass [Earth masses] -1-2 -3-4 Venus atmosphere mass Envelope mass 1 0 2 4 6 8 12 Time Time since since disk formation dissipation [Myr] [Myr] -5 0 2 4 6 8 12 Time Time since since disk formation dissipation [Myr] [Myr] -fast decrease from ~2 REarth to R=Rcore when envelope totally lost All these R(time) curves are not directly observationally constrained
Mstar=1 Msun, isothermal type I migration rate x 0.1, cold accretion. 1 embryo/disk, no special inflation mechanisms. Temporal evolution of the a-m diagram Output of core accr. population synthesis Only thermodynamic evolution Not dynamics Thermodynamic evolution (cooling & contraction) in time w. atmos. escape Close-in, low-mass loose the envelope. Most of the action early on. Jin et al. 2013 Black: Bare rocky cores a-m does not change much. (a>0.06 AU)
Mstar=1 Msun Isothermal Type I rate x 0.1. Cold accretion. 1 embryo/disk, no special inflation mechanisms. Temporal evolution of the a-r diagram Artifact of using Mmin=1 MEarth a-r does change! -Contraction -Evaporation -Empty valley below 1-2 REarth Black: Bare rocky cores
Radius distribution as a function of time 0.1 Gyr 1 Gyr Gyr Radius distribution as function of time: Key constraint for planet formation and evolution theory and Observed version by PLATO come back in 2030 :-) Have this in 2030 not from theory, but from PLATO data! 2 Radius alone sufficient No mass needed
Transition solid - gas rich planets Kepler: numerous close-in small planets: 49% of stars (P<0 d, R<4 R Earth ) Many are low-density planets (likely with a few percent of H/He) Important for formation theory, but also habitability At which mass and orbital distance is the transition? In principle simple solution with time dimension: Solid planets: mean density ~constant in time Not only giants planets Gaseous planets: mean density increases: contraction, evaporation Comparison with spectroscopy and dynamics of multiple planet systems
Transition solid - gas rich planets 0.1 0.1 2500 Equilibrium temperature 3 2000 1500 0.1 11 1200 00 Search for the 900 transition in the 800 M-rho-t space 700 1 1 exoplanets.org cf. Rauer et al. 2013 ce i re u P 1300 1 Gyr 0.1 Gyr Gyr 10 00 11 rth a E like 500 Mean density [g/cm 3] 3 Mean density [g/cm ] 3 Planetary Density [Grams/Centimeters ] exoplanets.org 11/1/2013 0 33 0[Earth Mass]00 Msin(i) 0 00 Mass [Earth masses] Mass [Earth masses] 1 Msun star. Initial conditions from population synthesis. 44 000 000 600 Giants: hotter less 500 dense: bloating 400 300 Low mass: hotter 200 denser: evaporation
Origin of close-in low-mass planets Essential open question for planet formation theory Rapid migration from beyond the iceline: ice-rich interior In situ formation or slower migration: rocky interior Mass-radius relation degenerate: iron/silicate/ice/h-he If we can rule out (observationally) that a subpopulation of planets can have a significant H/He atmosphere, break degeneracy
Origin of close-in low-mass planets Synthetic Observation Marcy et al. 2014 Planets with density of 2-3 g/cm 3 in the static part of the a-r (no time evolution i.e. no H/He envelope) must be icy
Conclusions -PLATO s ability to accurately determine the ages of the host stars adds a new class of constraints for formation theory -With the time dimension, it should become possible to observationally see -the transition from solid to gas-rich planets -the composition of close-in low-mass planets -This constrains several key concepts of planet formation theory like -efficiency of H/He accretion -orbital migration -The mass is sometimes not necessary for these new constrains: the radius and the age are sufficient