Planet formation in evolving protoplanetary discs

Bertram Bitsch, MPIA Heidelberg - 12.11.18

Abstract:

Observations of exoplanets have revealed a complex diversity in planetary systems regarding their masses, orbital configurations and number of planets. For example it has been shown that super-Earth planets are the most common planets in our galaxy even though we have no super-Earth in our own solar systems and that these planets are mostly in multiple systems. Hot Jupiters, on the other hand, are easy to detect, but are actually very rare objects. In addition new observations give indications about the chemical compositions of these planets. All these constraints have to be matched by theories of planet formation.

The formation of planetary cores of several Earth masses can be greatly accelerated by accreting objects of mm-cm size, so called pebbles. When the planetary cores have reached masses around 10 Earth masses, they can start to accrete gas from the protoplanetary disc and eventually form gas giants, like Jupiter and Saturn in our own solar system. During their formation, the planetary cores interact gravitationally with the disc and migrate through it. At the same time the protoplanetary disc evolves so that its temperature decreases, resulting in an inward movement of the water ice line. Previous simulations have also mostly followed the evolution of single planets, where multi-body dynamics have been ignored.

I will present here our new framework of planet formation that features a complex interplay between N-body dynamics, pebble accretion, planet migration, disc evolution and planetary instabilities after the gas disc phase. I will highlight the results of our new simulations and point to open questions that need to be answered in order to constrain planet formation theories even further.