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A planetesimal is a solid object arising during the accumulation of orbiting bodies whose internal strength is dominated by self-gravity and whose orbital dynamics is not significantly affected by gas drag. This corresponds to objects larger than approximately 1 km in the solar nebula.
The Chamberlin–Moulton planetesimal hypothesis was proposed in 1905 by geologist Thomas Chrowder Chamberlin and astronomer Forest Ray Moulton to describe the formation of the Solar System. It was proposed as a replacement for the Laplacian version of the nebular hypothesis that had prevailed since the 19th century.
A planetesimal is an object formed from dust, rock, and other materials, measuring from meters to hundreds of kilometers in size. According to the Chamberlin–Moulton planetesimal hypothesis and the theories of Viktor Safronov, a protoplanetary disk of materials such as gas and dust would orbit a star early in the formation of a planetary system.
Chamberlin–Moulton planetesimal hypothesis: Children: Rollin Thomas Chamberlin (1881–1948), geologist and skeptic of Wegener's continental drift hypothesis: Awards: Hayden Memorial Geological Award (1920) Penrose Gold Medal (1924) Penrose Medal (1927) Scientific career: Fields: Geology: Institutions: Columbian University University of ...
Nonetheless, formation via planetesimal collisions can be accomplished within the typical lifetime of a protoplanetary disc. [ 14 ] [ 15 ] The largest planetesimals can grow much faster via pebble accretion, [ 10 ] but if the formation or delivery of pebbles is rapid numerous Earth-mass planets form instead of a few giant planet cores. [ 16 ]
Planetesimal-driven migration is the result of the accumulation of the transfers of angular momentum during encounters between the planetesimals and a planet. For individual encounters the amount of angular momentum exchanged and the direction of the change in the planet's orbit depends on the geometry of the encounter.
Eventually, friction within the planetesimal disc made the orbits of Uranus and Neptune near-circular again. [47] [71] In contrast to the outer planets, the inner planets are not thought to have migrated significantly over the age of the Solar System, because their orbits have remained stable following the period of giant impacts. [38]
SDSS J1228+1040 b is a disputed [4] extrasolar planetesimal orbiting the white dwarf SDSS J1228+1040. It was discovered in 2019 using the variable calcium Ca II emission line. [2] Unlike other planetesimals around white dwarfs, the planetesimal SDSS J1228+1040 b needs high internal strength and a high density to not be tidally disrupted.