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Planetesimal

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Planetesimals
Planetesimals are small bodies of rock and/or ice that form by accretion in the protoplanetary disks of protostellar systems. These small objects continue to accrete and merge until finally a planetary system is formed.


Theory
Related Category: Astronomy: General
(pln´´ts´ml): see solar system.
More on Theory ...

Definition: planetesimals: Primordial bodies of intermediate size that accreted into planets or asteroids.
Space Tragedies9 Planets in Nine DaysAstronomy 101
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s are solid objects thought to exist in protoplanetary disks and in debris disks.

Planetesimal Compositions in Exoplanet Systems
Aug. 17, 2012 JOHNSON T., MOUSIS O., LUNINE J. & MADHUSUDHAN N.
ApJ, accepted
arxiv ...

Term given to objects in the early solar system that had reached the size of small moons, at which point their gravitational fields were strong enough to begin to influence their neighbors.

PLANETESIMAL HYPOTHESIS
The planetesimal hypothesis is a theory about the formation of the Solar System. It was proposed by Thomas Chrowder Chamberlain (Sept. 25, 1843 - Nov. 15, 1928), an American geologist and teacher.

S - Hypothetical solid celestial body that accumulated during the last stages of accretion.

planetesimal
A small body of primordial dust and ice from which the planets were formed.
plasma
A hot ionized gas.


a rocky and/or icy body, a few to several tens of kilometers in size, that was produced in the solar nebula.
Precambrian
a geological term denoting the time in Earth history prior to 570 million years ago.

Planetesimals: Bodies ranging in size from meters up to hundreds of kilometers in diameter that formed during the process that formed the planets by accretion. Most planetesimals accreted to form the planets.

: One of the small bodies that formed from the solar nebula and eventually grew into protoplanets.
plastic: A material with the properties of a solid but capable of flowing under pressure.

Planetesimals
Asteroid-sized solid bodies that are hypothesized to form when the protosolar nebula collapsed into a disk and fragmented. Most of the planetesimals subsequently accumulated into planets.
Planetocentric Coordinates ...

- A primordial solar system body of intermediate size that accreted with other s to form planets and satellites
Planetology - The comparative study of the properties of planets ...

Planetesimals that became modest in size but did not merge to form larger bodies became asteroids and comets.


A small body of rock and/or ice - under 10 kilometers (6 miles) across - formed during the early stages of the solar system. s are the building blocks of planets, but many never combined to form large bodies.

Planetesimals within the region which would become the asteroid belt were too strongly perturbed by Jupiter's gravity to form a planet. Instead they continued to orbit the Sun as before, while occasionally colliding.


A is a small object that orbits the Sun. s are thought to have formed when the Solar System itself formed, and they were perhaps the building blocks from which the planets were built.

planetesimal - (n.)
A small (diameter up to several hundred kilometers) solar-system body of the type that first condensed from the solar nebula. Planetesimals are thought to have been the principal bodies that combined to form the planets.


A solid object that is believed to exist in protoplanetary disks and in debris disks.

The planetesimals in the Oort Cloud and Kuiper Belt probably consist of chunks of rock mixed with frozen water and gases. Astronomer Fred Whipple once described them as "dirty snowballs.

Icy s formed in the outer solar system.
Composition Mainly ice and dust Orbits Highly elliptical, taking them very close to the Sun and back out into deep space, often far beyond the orbit of Pluto.

Large planetesimals were created as the new Sun's heat acted on nearby metal grains and chunks of rock during formation of the Solar System.

The Colliding s Theory: The interaction of earth-orbiting and Sun-orbiting s (very large chunks of rocks like asteroids) early in the history of the Solar System led to their breakup. The Moon condensed from this debris.

Comets are icy planetesimals usually from 1 to 50 km across and containing bits of fragile dust resembling carbonaceous chondrite material.

s small solid bodies believed to have formed during the condensing stage of the solar nebula. plasma hot ionized gas that is electrically conductive.

Within these disks, planetesimals collide and agglomerate into larger protoplanetary bodies that eventually form planets.

The theory by which s are assumed to collide with one another and coalesce, eventually sweeping up enough material to form the planets. [Silk90]
Achernar ...

Some of the initial planetesimals get ejected out beyond the orbit of Pluto to form the nuclei of the comets. The young sun continues to heat things up, and blows excess gas and dust out of the solar system.

The gravity of the s tended to divide the solar nebula into ring-shaped zones. This process explains item (i) above. F. More massive s had stronger gravity and could pull in more of the surrounding solar nebula material.

In regions where the average velocity of the collisions was too high, the shattering of planetesimals tends to dominate over accretion, preventing the formation of planet-sized bodies.

Comets also are cosmic debris, probably s that originally resided in the vicinity of the orbits of Uranus and Neptune rather than in the warmer regions of the asteroid belt.

Rocky planets are thought to have formed from the accretion of dust into 'planetesimals,' the planetesimals into proto-planets and finally the proto-planets into planets.

See also: See also: Planet, Astro, Solar, Orbit, Planetesimals

Astronomy  Planetary system  Planetesimals

 
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