 Besides mass , the elements heavier than helium can play a significant role in the evolution of stars . Astronomers label all elements heavier than helium " metals " , and call the chemical concentration of these elements in a star , its metallicity . A star 's metallicity can influence the time the star takes to burn its fuel , and controls the formation of its magnetic fields , which affects the strength of its stellar wind . 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 . Over time , such clouds become increasingly enriched in heavier elements as older stars die and shed portions of their atmospheres . 
 Besides mass , the elements heavier than helium can play a significant role in the evolution of stars . Astronomers label all elements heavier than helium " metals " , and call the chemical concentration of these elements in a star , its metallicity . A star <a href='null_genetive' title='1'><mark>'s</mark></a>metallicity can influence the time the star <a href='uninflect' title='2'><mark>takes</mark></a> to burn its fuel , and <a href='uninflect' title='3'><mark>controls</mark></a> the formation of its magnetic fields , which <a href='uninflect' title='4'><mark>affects</mark></a> the strength of its stellar wind . Older , population II stars <a href='got' title='5'><mark>have</mark></a> substantially less metallicity than the younger , population I <a href='uninflect' title='6'><mark>stars</mark></a> due to the composition of the molecular clouds from which they formed . Over time , such clouds become increasingly enriched in heavier elements as older stars die and shed portions of their atmospheres . 
Besides mass , the elements heavier than helium can play a significant role in da evolution of stars . Astronomers label all elements heavier den helium " metals " , and call tdachemical concentration of these elements in a star , its metallicity . A star  metallicity can influence the time thdatar take to burn its fuel , and control the formation of its magnetic fields , which affect the strength of its stellar wind . Older , population II stars got substantially less metallicity tdenthe younger , population I star due to thedamposition of the daecular clouds from which they formed . Over time , such clouds become increasingly enriched in heavier elements as older stars die and shed portions of their atmospheres .