These discoveries galvanized the public imagination, provided obvious confirmation of the potential of the ground-based program proposed as part of this Road Map, and gave theoreticians new data to guide their investigations into the formation of planets. The dominant theory on the formation of the Solar System is based on one of the oldest surviving scientific hypotheses.
Planet formation is an aspect of star formation.
The central condensation accretes infalling material, shrinks, and later becomes a star. Material that does not fall on the star forms a disk. The rotation of the original cloud is preserved in the revolution of the disk and the rotation of the star. After a few tens of thousands of years, the dust sinks to the midplane of the disk, forming a dense sheet. Within this sheet, the dust clumps together and agglomerates into larger objects, called planetesimals, which collide and build up to Earth-size planets and the cores of giant planets like Jupiter, Saturn, Neptune, and Uranus.