Our solar system is believed to have formed from a cloud of gas and dust, the so-called solar nebula, which began to condense on itself gravitationally ~ 4.6 billion years ago. As this cloud contracted, it began to spin and shaped itself into a disk revolving about the highest gravity mass at its center, which would become our sun. Our solar system inherited all of its chemical composition from an earlier star or stars which exploded as supernovae. Our sun scavenged a general sample of this material as it formed, but the residual material in the disk began to migrate based on its propensity to freeze at a given temperature.