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 (far right) which has ignited under its own weight. The remaining gas and dust form a rotating disc around this newly-born Sun. Accretion (slow gravitational attraction) of the disc material leads to the slow formation of the planets. Three gas giants (seen from above) are forming in the disc. One (centre left) has cleared the gas from its orbit (darker band) and is now attracting gas from either side.