Runaway gas accretion

Rapid envelope growth after cooling and envelope self-gravity allow gas capture to accelerate. It requires an available disk gas supply; eventually disk transport, gap formation or protoplanetary disk dispersal can limit growth. It differs from solid-body runaway planetesimal growth.

The epoch when the gaseous envelope mass becomes comparable with the solid core mass. Envelope self-gravity then changes structure and can accelerate gas capture through cooling and contraction. Crossover is a useful stage in classical models, rather than a universal core mass independent of opacity and accretion history.