COLLOQUIUM Marcus Brüggen, Universität Hamburg

Resonant chains architectures and exoplanetary archaeology: the case of TRAPPIST-1

 Resonant multi-planet systems occupy a privileged role at the interface of observation and theory of exoplanetary science. Observationally, (near-)resonance pairs produce large, coherent transit-timing variations that allow precise mass and dynamical constraints. Theoretically, they pose a puzzle: while protoplanetary-disc-driven convergent migration readily produces compact resonant chains in models, many appear fragile to post-gas instabilities. Thus, the few remaining resonant chains are the ones that encode a system's migration and damping history and thus act as fossils of its protoplanetary environment. TRAPPIST-1, a ~7 Gyr-old red dwarf, is a particularly exciting example. It hosts a 7-planet resonant chain, the longest known so far, with period ratios of neighbouring pairs close to 8:5, 5:3, 3:2, 3:2, 4:3, and 3:2 in increasing distance from the star. This compact, resonant configuration is a manifest sign of disc-driven migration; however, the preferred outcome of such evolution is the establishment of first-order resonances, not the high-order resonances observed in the inner system. We explain the observed orbital configuration in a model with two key elements: i) the inner, magnetically-truncated edge of the protoplanetary disc receded in time; and ii) the system was initially separated in two sub-systems. This allows us to probe deeper into the assembly of planetary systems as well as the currently unobserved physical conditions at the inner edge of the disc.

Talk in presence and via Zoom:

https://uni-hamburg.zoom.us/j/66006535328?pwd=aGkrSjJIYmZjK0VpYlpGL0ZrdHg2UT09