So I heard a theory once that a planet, gaining mass through collisions, could over time become a feelble star (if it gained about 10x the mass of jupiter), through adding kinetic energy and pressure, etc., and that this would create nuclear ignition. My question is this: If somehow we could fabricate a way to add mass to a planet that was this size, would it be possible to instigate nuclear ignition over a relatively short period of time? (nevermind how we would add the mass). Also, would the fuel (hydrogen, etc.) be found naturally in the planet, or would it be scarce and immediately collapse, or what?