 For at least a portion of its life , a star shines due to thermonuclear fusion of hydrogen into helium in its core , releasing energy that traverses the star 's interior and then radiates into outer space . Almost all naturally occurring elements heavier than helium are created by stellar nucleosynthesis during the star 's lifetime , and for some stars by supernova nucleosynthesis when it explodes . Near the end of its life , a star can also contain degenerate matter . Astronomers can determine the mass , age , metallicity ( chemical composition ) , and many other properties of a star by observing its motion through space , its luminosity , and spectrum respectively . The total mass of a star is the main factor that determines its evolution and eventual fate . Other characteristics of a star , including diameter and temperature , change over its life , while the star 's environment affects its rotation and movement . A plot of the temperature of many stars against their luminosities produces a plot known as a Hertzsprung – Russell diagram ( H – R diagram ) . Plotting a particular star on that diagram allows the age and evolutionary state of that star to be determined . 
 For at least a portion of its life , a star <a href='uninflect' title='1'><mark>shines</mark></a> due to thermonuclear fusion of hydrogen into helium in its core , releasing energy <a href='null_relcl' title='2'><mark>that</mark></a><a href='uninflect' title='3'><mark>traverses</mark></a> the star <a href='null_genetive' title='4'><mark>'s</mark></a>interior and then <a href='uninflect' title='5'><mark>radiates</mark></a> into outer space . Almost all naturally occurring elements heavier than helium are created by stellar nucleosynthesis during the star <a href='null_genetive' title='6'><mark>'s</mark></a>lifetime , and for some stars by supernova nucleosynthesis when it <a href='uninflect' title='7'><mark>explodes</mark></a> . Near the end of its life , a star can also contain degenerate matter . Astronomers can determine the mass , age , metallicity ( chemical composition ) , and many other properties of a star by observing its motion through space , its luminosity , and spectrum respectively . The total mass of a star <a href='drop_aux' title='8'><mark>is</mark></a>the main factor <a href='null_relcl' title='9'><mark>that</mark></a><a href='uninflect' title='10'><mark>determines</mark></a> its evolution and eventual fate . Other characteristics of a star , including diameter and temperature , change over its life , while the star <a href='null_genetive' title='11'><mark>'s</mark></a>environment <a href='uninflect' title='12'><mark>affects</mark></a> its rotation and movement . A plot of the temperature of many stars against their luminosities <a href='uninflect' title='13'><mark>produces</mark></a> a plot known as a Hertzsprung – Russell diagram ( H – R diagram ) . Plotting a particular star on that diagram <a href='uninflect' title='14'><mark>allows</mark></a> the age and evolutionary state of that star to be determined . 
For at least a portion of its life , a star shine due to thermonuclear fusion of hydrogen into helium in its core , releasing energy traverse da star  interior and then radiate into outer space . Almost alll naturally occurring elements heavier than helium are created by stellar nucleosynthesis durin tdastar  lifetime , and for some stars by supernova nucleosynthesis when it explode . Near the end of its life , a star can also contain degenerate matter . Astronomers can determine the mass , age , metallicity ( chemical composition ) , and many other properties of a star by observing its motion thru space , its luminosity , and spectrum respectively . The total mass of a star the main factor determine its evolution and eventual fate . Other characteristics of a star , including diameter and temperature , change over its life , while the star  environment affect its rotation and movement . A plot of the temperature of many stars against their luminosities produce a plot known as a Hertzsprung – Russell diagram ( H – R diagram ) . Plotting a particular star on that diagram allow the age and evolutionary state of that star to b determined .