What is the primary composition of a molecular cloud before stellar birth?
Answer
Hydrogen and Helium
Molecular clouds, which astronomers also term nebulae, serve as the raw material for star formation. Their composition closely mirrors the early universe, consisting overwhelmingly of the two lightest elements. Specifically, these clouds in the Milky Way today are about 71% hydrogen and 27% helium by mass. All elements heavier than helium, which are the products of previous stellar generations, collectively make up only a small fraction and are generally grouped under the astronomical term 'metals'.
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