Formation of TRAPPIST-1 and other low-mass planetary systems

Astronomy Unit Seminars
Chris Ormel
Sijme-Jan Paardekooper
September 29th, 2017 at 14:30
GO Jones Room 610

TRAPPIST-1 is a tiny, 0.08 solar-mass, M-star. Yet it hosts a planetary system comprising at least 7 (sub-)Earth planets, all residing within 0.1 au. I present a scenario for the formation of TRAPPIST-1 and other similar planetary systems.  In our scenario we envision that planet formation commenced at the H2O iceline by streaming instabilities. Further growth proceeded by efficient accretion of mm to cm-size particles (pebbles) that drifted from the outer disk. This scenario has several advantages: it connects to the observation that disks are filled with pebble-size particles, it is efficient, it explains why the TRAPPIST-1 planets are ~Earth mass, and it provides a rationale for the system’s architecture. I will discuss new insights developed by our group on key processes that enter the model -- e.g., the physics of the H2O ice line or pebble accretion efficiencies. I end with a discussion on how universal the ensuing planet formation paradigm could be.