We discuss the formation of a dusty accretion disk around an infant star and, from that, the planets. Telescopic observations of young stars suggest planet formation required only a few tens of millions of years, in agreement with a Solar System timescale based on measurements of radioactive isotopes in meteorites. The age of the Solar System, 4.567 billion years, is determined from calcium–aluminum inclusions (CAIs), the first-formed solids. Numerical simulations of planetary accretion further support this timescale and constrain the widths of feeding zones. The compositions of the terrestrial planets are broadly chondritic, but depletions in volatile elements suggest their assembly from already differentiated planetesimals. The ice giants have rocky cores that directly accreted nebular ices, and the even more massive gas giants have ice giant-like cores that swept up nebular gas. Leftover planetary building blocks – asteroids and comets – provide more detailed insights into planet formation processes. We complete this story by discussing the origin of the Moon by a giant impact, and the related topic of orbital perturbations possibly caused by migrations of the giant planets.
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