Creating Extreme Solar Systems through stellar flybys

It is now well established that stellar flybys occur within stellar cradles. Therefore, the process of planet formation around young stellar objects does not occur in isolation. More specifically, this kind of encounters dramatically affect the protoplanetary discs where planets born. Here we show in detail the dynamical and observational signatures of flybys: warps, spirals, shadows & misalignments. These results allow us to interpret several very recent (unpublished) ALMA and VLT observations of discs exhibiting mysterious asymmetries (e.g. FU Ori, AS 205, UX Tau, SR 24). We have strong reasons to believe that we are currently witnessing interacting discs. This very fact raises others fundamental questions: What is the effect of the environment on planet formation? How frequent are these encounters? Did the Solar System experience such a flyby? To conclude, we discuss the importance of flybys in producing Extreme Solar Systems.