Protoplanet

Common card · No. 364949

A protoplanet or planetary embryo is an astronomical body originated within a protoplanetary disk that has undergone internal melting to produce a differentiated interior. Protoplanets are thought to form out of kilometre-sized planetesimals that gravitationally perturb each other's orbits and collide, gradually coalescing into larger bodies through a process known as "runaway growth". Once accumulated enough mass, protoplanets will begin to assume a spherical shape due to hydrostatic equilibrium and become dwarf planets, those of which that subsequently succeed in dominating their own orbit will become planets proper. An alternative formation pathway of protoplanets is a process called disk fragmentation. Formation by this process, also called gravitational (disk) instability, is favoured for giant planets on wide orbits.

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