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The 1944 accretion model by Otto Schmidt was further developed in a quantitative way in 1969 by Viktor Safronov. [4] He calculated, in detail, the different stages of terrestrial planet formation. [5] [6] Since then, the model has been further developed using intensive numerical simulations to study planetesimal accumulation.
This process increases the cross section over which the large bodies can accrete material, accelerating their growth. The rapid growth of the planetesimals via pebble accretion allows for the formation of giant planet cores in the outer Solar System before the dispersal of the gas disk.
The disk eventually disappears due to accretion onto the central star, planet formation, ejection by jets and photoevaporation by UV-radiation from the central star and nearby stars. [48] As a result, the young star becomes a weakly lined T Tauri star, which slowly, over hundreds of millions of years, evolves into an ordinary Sun-like star. [38]
The process of accretion, therefore, is not complete, and may still pose a threat to life on Earth. [ 82 ] [ 83 ] Over the course of the Solar System's evolution, comets were ejected out of the inner Solar System by the gravity of the giant planets and sent thousands of AU outward to form the Oort cloud , a spherical outer swarm of cometary ...
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A group of the world's leading planet formation experts decided at a conference in 2006 [8] on the following definition of a planetesimal: 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 ...
Observations suggest that gas in protoplanetary disks orbiting young stars have lifetimes of a few to several million years. [1] If planets with masses of around an Earth mass or greater form while the gas is still present, the planets can exchange angular momentum with the surrounding gas in the protoplanetary disk so that their orbits change gradually.
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.