68973
Older , population II stars have substantially less metallicity than the younger , population I stars due to the composition of the molecular clouds from which they formed .
 population II
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 population II