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Pebble accretion may accelerate the formation of planets by a factor of 1000 compared to the accretion of planetesimals, allowing giant planets to form before the dissipation of the gas disk. [ 28 ] [ 29 ] However, core growth via pebble accretion appears incompatible with the final masses and compositions of Uranus and Neptune . [ 30 ]
In a protoplanetary disk, the probability of accretion of pebbles ranging in size from centimeters to a meter is ≤10% on planets up to about 20 Earth masses. [1] A protoplanetary disk is made up of a mix of gas and solids including dust, pebbles, planetesimals, and protoplanets. [2]
[22] [34] The latter scenario is thought to be the most promising one, because it can explain the formation of the giant planets in relatively low-mass disks (less than 0.1 M ☉). [34] In this model giant planet formation is divided into two stages: a) accretion of a core of approximately 10 M E and b) accretion of gas from the protoplanetary ...
The currently accepted method by which the planets formed is accretion, in which the planets began as dust grains in orbit around the central protostar. Through direct contact and self-organization , these grains formed into clumps up to 200 m (660 ft) in diameter, which in turn collided to form larger bodies ( planetesimals ) of ~10 km (6.2 mi ...
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The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a young protostar orbited by a protoplanetary disk. Planets grow in this disk by the gradual accumulation of material driven by gravity, a process called accretion.
A primary atmosphere is an atmosphere of a planet that forms by accretion of gaseous matter from the accretion disc of the planet's sun. Planets such as Jupiter and Saturn have primary atmospheres. Primary atmospheres are very thick compared to secondary atmospheres like the one found on Earth.
The objects formed by accretion are called planetesimals—they act as seeds for planet formation. Initially, planetesimals were closely packed. Initially, planetesimals were closely packed. They coalesced into larger objects, forming clumps up to a few kilometers across in a few million years, a small time in comparison to the age of the Solar ...