After the star enters the main sequence stage , energy comes from nuclear fusion , the combination of several small nuclei into a large nucleus . in contrast , the nuclear plants on earth generate energy by nuclear fission , the splitting of a large nucleus to several smaller ones 只要星体进入主序星阶段，能量转为来自核聚变相反地地球上的核电厂使用的是核裂变，即大原子核分裂为众多小原子核，过程中释放能量的机制。
Particles in the star move around rapidly due to high temperature creating a high gas pressure . together with the radiation pressure generated by the photons , they exert pressure pushing outward to balance gravity s inward pull . then , a star becomes stable and now enters the main sequence phase 恒星内部所产生的高温，会令粒子急剧运动，产生向外的气体压力，再加上光子的辐射压力抵消掉向内的引力，令恒星保持稳定，进入主序星阶段。
For a - early f type ms stars , stellar chromospheric activity decrease with stellar rotation period , but increase with rossby number ; for m type ms stars , stellar chromospheric activity increase with stellar rotation period and rossby number , and stellar chromospheric activity reach saturation at large color index ; for the ms stars between mid - f to m type , stellar chromospheric activity decrease with stellar rotation period and rossby number A ?早f型主序恒星的自转周期和恒星对流区的随色指数的分布明显地影响着这些恒星的色球活动行为。而m型主序星的色球活动水平基本上随自转参量的增大呈上升趋势，并且m型主序星的色球活动水平在色指数较大时趋于饱和。
