Planetary formation. Artwork of protoplanets being formed by the process of accretion in the early solar system. It is thought that the Sun and the planets formed from a cloud of gas and dust around 4. 6 billion years ago. Gravitational condensation of this cloud (or nebula) formed a protostar (upper left) which has ignited under its own weight. The remaining material forms a rotating disc around this newly-formed Sun. Accretion (slow gravitational attraction) of the disc material forms the planets. Four planets (white) are seen forming in the solar disc. A gas giant (centre right) has cleared the gas from its orbit (darker band) and is now attracting gas from either side.