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A protoplanet is a large planetary embryo that originated within a protoplanetary disk and has undergone internal melting to produce a differentiated interior. Protoplanets are thought to form out of kilometer-sized planetesimals that gravitationally perturb each other's orbits and collide, gradually coalescing into the dominant planets .
Atacama Large Millimeter Array image of HL Tauri [1] [2]. A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star.
Protoplanet: A large planetary embryo that originates within protoplanetary discs and has undergone internal melting to produce differentiated interiors. Protoplanets are believed to form out of kilometer-sized planetesimals that attract each other gravitationally and collide. PDS 70 b and c, AB Aurigae b: Puffy planet
The huge indent, called the 'imbrue basin,' stretches across 750 miles.
The dividing line between a planetesimal and protoplanet is typically framed in terms of the size and the stages of development that the potential planet has already gone through: planetesimals combine to form a protoplanet, and protoplanets continue to grow (faster than planetesimals). [13] [14] [15]
Vesta is the only known remaining rocky protoplanet (with a differentiated interior) of the kind that formed the terrestrial planets. [24] [25] [26] Numerous fragments of Vesta were ejected by collisions one and two billion years ago that left two enormous craters occupying much of Vesta's southern hemisphere.
The accretion model that Earth and the other terrestrial planets formed from meteoric material was proposed in 1944 by Otto Schmidt, followed by the protoplanet theory of William McCrea (1960) and finally the capture theory of Michael Woolfson. [3]
In 1944, German chemist and physicist Arnold Eucken considered the thermodynamics of Earth condensing and raining-out within a giant protoplanet at pressures of 100–1000 atm. In the 1950s and early 1960s, discussion of planetary formation at such pressures took place, but Cameron's 1963 low-pressure (c. 4–10 atm.) model largely supplanted ...