4.4 Formation of the Solar System
Nebular Theory of Formation
The most widely accepted theory of formation of the solar system is the nebular theory. This theory states that the solar system was formed during the gravitational collapse of a nebula (a cloud of dust and gas) about 4.5 billion years ago. The process involved in the theory is outlined below.
Gravitational Collapse
A nebula was disturbed in some way, possibly by the explosion, or supernova, of a nearby star. This disturbance caused the beginning of gravitational collapse, whereby the particles in the nebula are attracted to one another by gravity.
Spin
The cloud condensed further and further. As the cloud condensed, it began to spin. The more it condensed, the faster it spun. More massive particles were pulled to the centre of the nebula, while lighter particles remained in the dust clouds of the outer nebula.
Flattening
Due to multiple forces acting on the spinning nebula, it began to flatten out into a disc shape with a bulge at the centre. This is like when a chef takes a ball of pizza dough and twirls it in the air. The dough flattens out into a large disc.
