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Related to planetesimals: Planetesimal theory


(plan-ĕ-tess -ă-mălz) Bodies, ranging in size from less than a millimeter to many kilometers, that are thought to have formed the planets of the Solar System by a process of accretion.



the tiny solid particles that were the material for the formation of the planets according to the cosmogonical hypothesis advanced at the turn of the century by the American scientists F. Moulton and T. Chamberlin. The hypothesis attributed the formation of planetesimals to the cooling and condensation of matter ejected by the sun. This assumption, however, is not valid, since it is incapable of explaining the large distances and specific angular momenta of the planets. The term “planetesimal” is sometimes used in modern cosmogonical hypotheses and theories that consider the formation of the planets from solid particles.

References in periodicals archive ?
So the fact that we can still see these disks around a 10- to 20-million-year-old star means that the dust is being replenished by collisions between planetesimals.
It is though Earth was likely formed from a collection of planetesimals that had already lost their atmospheres.
Whether the four inner planets or a migrating Jupiter nudged the planetesimal toward the asteroid belt is unclear, the team reports.
Welsh summarized the current theory of planet formation as "interstellar dust under the influence of gravity becomes blobs, and the blobs grow into rocks, the rocks coalesce and become bigger things - planetesimals and comets - and finally, you get planets.
Ozernoy and Ipatov have estimated the number of planetesimals that were flung at the early Earth from reservoirs of such bodies following orbits inside Jupiter's path or crossing it.
Johnson and Li found that the formation of planetesimals can only take place once a minimum metallicity is reached in a protostellar disk.
New observations by Aki Roberge of Johns Hopkins University in Baltimore and her colleagues suggest that a mere stripling of a star, which might be as young as 300,000 years, already has planetesimals.
But if the fraction of pebbles is increased slightly, the clumping increases dramatically and quickly results in the accretion of sufficient material to make larger-scale planetesimals.
They propose that bits of dust within the disk of material that surrounded the infant sun assembled "into planetesimals many kilometers across over a time interval of order 1 million years or less," says Jack J.
Renu Malhotra of the Lunar and Planetary Institute in Houston and Norman Murray of the Canadian Institute for Theoretical Astrophysics in Toronto and their colleagues propose that migration begins well after the gas in the protoplanetary disk has dispersed, leaving behind fully fledged planets and a debris field of boulder-size remnants called planetesimals.
The results come from new simulations using a theory called the Nice model, which suggests the solar system's giant planets were born closer together and were surrounded by a vast disc of leftovers from the planets' formation called planetesimals.
This finding--the first accurate measurement of the density of a carbonaceous asteroid--could prompt a reassessment of the geophysical history of these wandering planetesimals.