Explanation: Formation of Planets

The following are considered to be the stages in the development of planets:

• The stars are localised lumps of gas within a nebula. The gravitational force within the lumps leads to the formation of a core to the gas cloud and a huge rotating disc of gas and dust develops around the gas core.
• In the next stage, the gas cloud starts getting condensed and the matter around the core develops into small-rounded objects.
• These small-rounded objects by the process of cohesion develop into what is called planetesimals. Larger bodies start forming by collision, and gravitational attraction causes the material to stick together. Planetesimals are a large number of smaller bodies.
• In the final stage, these large number of small planetesimals accrete to form a fewer large bodies in the form of planets.

Source: NCERT Class 11