Astronomy Practice Exam 2025 – Complete Preparation Guide

The main premise of the rotating nebula theory is that a rotating cloud of gas and dust, often referred to as a nebula, collapsed under its own gravity, leading to the formation of the solar system. This idea suggests that as the nebula contracted, it began to spin and flatten out into a disk shape, where most of the material concentrated in the center to form the Sun, while the remaining material within the disk gradually coalesced into the planets.

This process was driven by gravitational forces and allowed the planetesimals to collide and stick together, forming larger bodies that would become the planets. The theory provides a comprehensive explanation for the observed structure of our solar system, including the orbits of the planets and their formation from a common protostellar material. Hence, the theory helps to understand not just the origin of the solar system, but also the processes by which celestial bodies form in general.