A solar nebula is a large cloud of gas and dust in space that is believed to be the birthplace of stars and planetary systems. This cloud, primarily composed of hydrogen and helium, collapses under its own gravity, leading to the formation of a dense core. As the core contracts, it heats up, eventually igniting nuclear fusion and creating a new star, such as our own Sun. Surrounding the newly formed star, the remaining material in the solar nebula can clump together to form planets, moons, and other celestial bodies. This process is essential for understanding the formation of our Solar System and the origins of various planetary bodies.