What explains the metallicity difference between population I and population II stars?
A. Population I stars formed in regions of the MWG where heavy elements were plentiful. Population II stars formed in regions of the MWG where heavy elements were scarce. As a result of their location of formation, the two populations have differing metallicities.
B. Population II stars are older than population II star and have therefore had a much longer time to produced heavy elements.
C. Population II stars formed when the abundance of elements heavier than hydrogen and helium was low. Population I stars formed later, after mass lost by dying members of the first generations of stars had enriched the interstellar medium with elements heavier than hydrogen and helium.
D. Population I stars are of a spectral type like our Sun or possibly cooler. Population II stars are of a spectral type that is hotter than our Sun. Heavier elements form in the hotter, more massive stars, causing the metallicity difference between the two populations.
Answer: C. Population II stars formed when the abundance of elements heavier than hydrogen and helium was low. Population I stars formed later, after mass lost by dying members of the first generations of stars had enriched the interstellar medium with elements heavier than hydrogen and helium.
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?
?
a.
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