Single migrating planet forms multi-ring dust structures to 150 au at α≤10^{-4}

The team ran locally isothermal 2D hydro models varying aspect ratio, α from 10^{-3} to 10^{-5}, and planet mass. The planet opens a primary gap, stalls near 50 au, and at low viscosity launches secondary spirals that carve inner gaps while type-III episodes deposit partial outer gaps whose pressure maxima trap dust into rings or vortices.

These structures match ALMA multi-ring systems only when α≤10^{-4}; at α=10^{-3} the type-III rings dissipate in <100 kyr. The work shows migration need not erase outer rings because stalling plus secondary and remnant gaps together populate the observed radial range.

Earlier analytic migration studies assumed steady type-II drift without type-III bursts or secondary spiral gaps; the new parameter sweep reveals that vortex lifetimes and ring persistence both lengthen sharply below α=10^{-4}, a threshold rarely reached in 3D stratified models. This implies current ALMA ring statistics may undercount low-viscosity discs.

Longer 3D runs including dust coagulation and radiative cooling are required before ring-to-vortex ratios can be compared directly with DSHARP and AGE-PRO surveys.