Stars and Stellar Evolution

m i j N k F> 1.15 M ) . . ... .. .. ... .. .. 133init 9.3 Whyandhowdoesastarbecomeredgiant?. ... .. .. ... .. .. ... .. .. 134 9.3.1 A “gedankenexperiment”: the gravothermal hysteresis cycle . . . . . . . . . 134 9.3.2 Thehysteresiscycleandrealstars . . ... .. .. ... .. .. ... .. .. 136 9.3.3 Asecondredgiantphase ... .. .. ... .. .. ... .. .. ... .. .. 137 9.4 The overall stellar thermal equilibrium (STE) . . . . . . . . . . . . . . . . . . . . . 137 9.5 Isothermal He core and Sch¨onberg-Chandrasekharlimit . ... .. .. ... .. .. 139 9.6 Luminosityevolutionofredgiants . . . . . . ... .. .. ... .. .. ... .. .. 139 9.6.1 Red giant luminosity depends on M ... .. .. ... .. .. ... .. .. 139init 9.6.2 Effects of metallicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 9.7 Thecoredrivestheevolution,theenvelopefollows .. .. ... .. .. ... .. .. 140 9.8 Durationofthemain-sequencephase . . . . . ... .. .. ... .. .. ... .. .. 140 10 Stellar evolution: Stars in the lower mass range 141 10.1 Definingthelowmassrange. .. ... .. .. ... .. .. ... .. .. ... .. .. 141 10.1.1 The MS-mass limit of 1.15 M . . . ... .. .. ... .. .. ... .. .. 141 10.1.2 The MS-mass limit of 0.5M . . . ... .. .. ... .. .. ... .. .. 143 10.2 Hshellburning: theredgiantphase . . . . . ... .. .. ... .. .. ... .. .. 143 10.2.1 Evolution of the RG core and of the H-burning shell . . . . . . . . . . . . . 144 10.2.2 The RG surface: spectral lines, mass loss and dust . . . . . . . . . . . . . .