 The time a star spends on the main sequence depends primarily on the amount of fuel it has and the rate at which it fuses it . The Sun 's is expected to live 10 billion ( <unk> ) years . Massive stars consume their fuel very rapidly and are short @-@ lived . Low mass stars consume their fuel very slowly . Stars less massive than 0 @.@ 25 M ☉ , called red dwarfs , are able to fuse nearly all of their mass while stars of about 1 M ☉ can only fuse about 10 % of their mass . The combination of their slow fuel @-@ consumption and relatively large usable fuel supply allows low mass stars to last about one trillion ( 1012 ) years ; the most extreme of 0 @.@ 08 M ☉ ) will last for about 12 trillion years . Red dwarfs become <unk> and more luminous as they accumulate helium . When they eventually run out of hydrogen , they contract into a white dwarf and decline in temperature . However , since the lifespan of such stars is greater than the current age of the universe ( 13 @.@ 8 billion years ) , no stars under about 0 @.@ 85 M ☉ are expected to have moved off the main sequence . 
