Chapter​ ​16​ ​–​ ​Star​ ​Birth Stellar​ ​Evolution ● Stars​ ​are​ ​like​ ​ppl​ ​in​ ​that​ ​they​ ​are​ ​born,​ ​grow​ ​up,​ ​mature​ ​&​ ​die ● Star’s​ ​​mass​​ ​determines​ ​what​ ​life​ ​path​ i​ t​ ​will​ ​take ● We​ ​divide​ ​all​ ​stars​ ​into​ ​3​ ​groups: o Low​ ​mass​ ( ​ .08​​ ​ ​of​ ​sun​ ​​ ​ ​M) ● H-R​ ​diagram​ ​makes​ u ​ seful​ ​ ap ● Life​ o ​ f​ ny​ ​star​ ​​ ​ ​battle​ f​ ​2​ ​forces: o Gravity​ ​vs.​ ​“something​ ​else” ● Gravity​ ​always​ ​wants​ t ​ o​ ​collapse​ tar o The​ “ ​ something​ ​else”​ ​holds​ ​up​ ​ tar o Type​ i ​ s​ ​st​ s​ ​defined​​ y​ ​“something​ e​ lse” ● Remember:​ ​Newton’s​ ​law​ ​of​ ​gravity o Amnt.​ ​Of​ ​gravitational​ ​force​ ​depends​ o ​ n​ ​mass o Gravitational​ ​potential​ ​energy​ ​into​ ​heat​ ​as​ ​star​ ​collapses The​ ​ tellar​ ​Womb ● Stars​ ​born​ d ​ eep​ ​in​​ olecular​ ​clouds o Cold​ ​(10​ ​–​ ​ 0​​ )​ ​dense​ ​nebulae o So​ ​cold​ ​that​ ​H2​​ ​can​ ​exist ● Cold​ ​cloud​ c ​ an​​ ragment Stellar​ ​Gestation ● Something​ ​happens​ ​to​ ​perturb​ ​a​ ​molecular​ ​cloud​ ​&​ ​make​ ​it​ ​begin​ ​to​ ​fragment ● As​ ​core​ ​of​ ​ as​ ​collapses,​​ t​ ​heats​ ​up o Radiates​ ​infrared​ ​from​ ​its​ ​surface o Protostar ● Protostar​ ​collapses​ ​until​ ​its​ ​core​ ​reaches​ ​10​ ​ ​K​ ​