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Before the Solar System existed, there was an even larger cloud of gas and dust. Most of the elements in the present Solar System were present in that cloud, such as hydrogen, helium, carbon, oxygen, copper, gold and iron.

Hydrogen is a primordial element, but from where did the heavier elements come? There is some primordial helium, and further helium is a result of stellar fusion from stars that existed before the Sun. Oxygen and carbon also formed from past stellar fusion. Iron is the end product of stellar fusion. Elements heavier than iron require more extreme processes to form, such as the explosion of stars into supernovae.

The pre-Solar cloud began to contract due to the force of gravity. Eventually it formed into a giant disk. Most of the mass aggregated at the center of the disk and began to heat up.

 

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