Nebular Hypothesis

The nebular hypothesis is the widely accepted model for the formation of the Solar System, proposing that the Sun and planets condensed from a single, rotating cloud of gas and dust that collapsed under its own gravity, flattening into a disk from which the Sun formed at the center and the planets accreted from the remaining material. First proposed in versions by Emanuel Swedenborg, Immanuel Kant and Pierre-Simon Laplace in the eighteenth century, the modern form of the hypothesis is supported by direct observations of protoplanetary disks around other young stars. It explains why the planets orbit the Sun in roughly the same plane and direction, a pattern that a purely random formation process would not naturally produce.