  Quantum excitations in lattice systems always propagate at a finite maximum
velocity. We probe this mechanism by considering a defect travelling at a
constant velocity in the quantum Ising spin chain in transverse field.
Independently of the microscopic details of the defect, we characterize the
expectation value of local observables at large times and large distances from
the impurity, where a Local Quasi Stationary State (LQSS) emerges. The LQSS is
strongly affected by the defect velocity: for superluminal defects, it exhibits
a growing region where translational invariance is spontaneously restored. We
also analyze the behavior of the friction force exerted by the many-body system
on the moving defect, which reflects the energy required by the LQSS formation.
Exact results are provided in the two limits of extremely narrow and very
smooth impurity. Possible extensions to more general free-fermion models and
interacting systems are discussed
