Photoevaporative gap opening
= Photoevaporative gap opening
When a <protoplanetary disk>'s inward viscous supply approaches its wind-loss rate, <photoevaporation> can prevent replenishment of the inner disk. That region drains on a <viscous timescale>, leaving a gap or hole. A negative density in a formal <steady state> calculation signals the breakdown of that approximation, not a physical continuation. An exposed outer edge can subsequently disperse rapidly.