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On the origin of the solar system and the exceptional position of the Sun in the Galaxy
Authors:L S Marochnik
Institution:1. Space Research Institute of U.S.S.R., Academy of Sciences, Moscow, USSR
Abstract:The solar system's position in the Galaxy is an exclusive one, since the Sun is close to the corotation circle, which is the place where the angular velocity of the galactic differential rotation is equal to that of density waves displaying as spiral arms. Each galaxy contains only one corotation circle; therefore, it is an exceptional place. In the Galaxy, the deviation of the Sun from the corotation is very small — it is equal to ΔR/R ≈0.03, where ΔR=R c ?R ,R c is the corotation distance from the galactic center andR is the Sun's distance from the galactic center. The special conditions of the Sun's position in the Galaxy explain the origin of the fundamental cosmogony timescalesT 1≈4.6×109 yr,T 2?108 yr,T 3?106 yr detected by the radioactive decay of various nuclides. The timescaleT 1 (the solar system's ‘lifetime’) is the protosolar cloud lifetime in a space between the galactic spiral arms. The timescaleT 2 is the presolar cloud lifetime in a spiral arm.T 3 is a timescale of hydrodynamical processes of a cloud-wave interaction. The possibility of the natural explanation of the cosmogony timescales by the unified process (on condition that the Sun is near the state of corotation) can become an argument in favour of the fact that the nearness to the corotation is necessary for the formation of systems similar to the Solar system. If the special position of the Sun is not incidental, then the corotation circles of our Galaxy, as well as those of other galaxies, are just regions where situations similar to ours are likely to be found.
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