Four and a half billion years ago the solar system was born. A vast cloud of cold gas and dust was disturbed and compressed forming the raw material of stars and planets. The cloud fragmented into smaller, denser pockets of matter and collapsed inward due to gravity.
Over 100 000 years one of the pockets (a nebula) condensed to the volume of today's solar system. In the dense center of the nebula a star formed (the sun). The rest of the nebula spread into a thin disk due to its slow spinning. Atoms and molecules within the nebula began form larger particles, and the sun determind which particles could exist.
Close to the sun, solar heat evaporated ices and prevented light weight elements from existing and the inner planets formed. These were dominated by rock and metal clumped together. Far from the sun, the ices remained intact and merged to form the core of the planets. As the planets grew, they swept up hydrogen and helium and grew further.
Most planets moons formed at the same time, but Earth's moon formed later, when a large body hit the planet, and blasted hot gas and molten rock into orbit. This later cooled and coalesced and became the Earth's moon.
Website by:
Bethany Jones
University of Bristol
email: bj0751@bristol.ac.uk