solarnebula

The solar nebula, or solarnebula, is the giant rotating cloud of gas and dust from which the Solar System formed. The concept is central to the solar nebula theory, also called the nebular hypothesis, developed from ideas by Kant and Laplace and refined by later astronomers. Observations of star-forming regions and young planetary systems support the idea of disks around nascent stars.

In the model, the solar nebula originated from a larger molecular cloud enriched by previous generations of stars. Gravitational collapse, aided by loss of angular momentum, caused the cloud to flatten into a protoplanetary disk with a central protosun. Material in the disk condensed to form planetesimals and eventually planets.

The nebula was primarily hydrogen and helium with heavier elements. Temperature within the disk decreased with distance from the Sun, creating zones where ices could form (the snow line). This led to rocky planets inside and gas giants beyond as solid cores accreted gas from the disk.

Over a few million years, gas dissipated as planets formed and the Sun ignited. Evidence includes isotopic compositions of meteorites, cratering records, and direct observations of young disks around other stars. The solar nebula model remains a foundational framework for studying planetary formation and the history of the Solar System.