How did solar system abundances arise

The solar system abundances of the elements are the result of the Big Bang, which produced hydrogen and helium, 7.5 billion years of stellar nucleosynthesis, which produced most of the rest of the elements, and the physical processes that mixed the materials together to form the Sun s parent molecular cloud. The unique features of the solar system composition may also reflect the stochastic events that occurred in the region where the Sun formed just prior to solar system formation. 

Differences between solar system and cosmic abundances 

Solar system Outer galaxy Galactic center 

160/170 in solar system material is -2630, whereas 1 /180 is -490. The 160 line often saturates, resulting in spurious results. However, 170/180 is -0.19 and thus is relatively easy to measure. Table 4.3 shows isotopic data for carbon, nitrogen, and oxygen for molecular clouds in the galactic center and the outer galaxy compared to the solar system ratios. 

Another possible way to reconcile some of the chemical and isotopic differences between the solar system and the solar neighborhood is to postulate that the solar system formed in a 

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