Definition
Planet formation is the process by which planetary bodies are formed from a disk of gas and dust around a protostar. Planets can form in two ways. In the regions far from the central star, where the disk can cool efficiently, giant gaseous planets might form as a result of the gravitational instability of the disk; alternatively, these planets may form from the protoplanetary cores discussed below. In the inner regions, planets are expected to form in a more complex, multistage process: first, the dust settles onto the disk’s midplane and coagulates to form asteroid- or comet-like bodies called planetesimals . Then, the planetesimals accrete with each other during low-velocity collisions to form planetary embryos or protoplanetary cores. The former are rocky bodies with masses of the order of the lunar to Martian mass, which form in the hottest region of the disk, where water is not in solid form. The protoplanetary cores, which form beyond the s...
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Morbidelli, A. (2014). Planet Formation. In: Amils, R., et al. Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-27833-4_1902-7
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DOI: https://doi.org/10.1007/978-3-642-27833-4_1902-7
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