= Gas recycling through a planetary envelope
<Gas recycling through a planetary envelope> is exchange between gas near an embedded <planetary embryo> and the surrounding <protoplanetary disk>. Gas can enter and leave the embryo's gravitational neighbourhood instead of remaining in a permanently closed atmosphere. A geometrical region influenced by the embryo therefore need not contain a fixed collection of captured material.
The relevant comparison is between replacement and cooling. If new disk gas replenishes a region faster than it can lose energy, recycling can interfere with <cooling-controlled planetary envelope growth>. Three-dimensional hydrodynamic simulations demonstrated such connected inflow and outflow around low-mass embedded bodies.<Hydrodynamics of embedded planets first atmospheres II: A rapid recycling of atmospheric gas by Chris W. Ormel and others>[Abstract and discussion of replenishment versus Kelvin-Helmholtz cooling times]{ref} The outcome depends on thermal structure and flow geometry; it is not a universal prohibition on gas capture by every core.
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