Chemical composition of giant exoplanets due to pebble, planetesimal and gas accretion: origin of the heavy elements


Recommended citation: Schneider & Bitsch (in prep)

Upcoming studies of extrasolar gas giants will give precise insights into the composition of planetary atmospheres. Previous research adopted either pebble- or planetesimal accretion for the growth of these planets to gain insights into the compositions of these planets.

We investigate in the final composition of planets formed in disks with different viscosities and solid fractions by pebble and planetesimal accretion to understand mechanisms that are responsible for the final composition of these planets.

To achieve this goal, we perform semi analytical 1D models of protoplanetary disks including the treatment of viscous evolution and heating, pebble drift and simple chemistry to simulate the growth of planets from planetary embryos to Jupiter mass objects by accretion of pebbles, planetesimals and gas while they migrate through the disk.

The gas phase of the protoplanetary disk is enriched due to the evaporation of evaporation line crossing pebbles. The accretion of planetesimals and the accretion of polluted gas enriches the planetary envelope with refractories and volatiles respectively. It is therefore possible to gain hints about the formation path of planets by comparing refractories and volatiles in the atmosphere.

We conclude that planetesimal accretion and pebble evaporation leave distinct signatures in planetary atmospheres which enable the tracing of possible formation pathways.