1、2018/7/20,,1,第三章 恒星的形成与演化,恒星形成恒星结构元素合成恒星演化超 新 星密近双星,http:/ TRUE OR FALSE?,Stars evolve along the main sequence.Brown dwarfs take a long time to form but will eventually arrive as stars on the lower main sequence.In star formation, more G, K, and M stars form than O and B stars.,2018/7/20,,2,2018/7/2
2、0,,4,初始质量函数(Initial Mass Function),Generally more low-mass than high-mass stars form when an interstellar cloud fragments.The stellar initial mass function (IMF) describes the probability of a star forming with a particular mass.,For Salpeter IMF, x =1.35,SELF-TEST: TRUE OR FALSE?,All the red dwarf
3、stars that ever formed are still on the main sequence today.As a star evolves away from the main sequence it gets hotter. A planetary nebula is the disk of matter around a star that will eventually form a planetary system,2018/7/20,,5,SELF-TEST: TRUE OR FALSE?,For a high-mass star there is no helium
4、 flashThe spectrum of a Type II supernova shows the presence of lots of hydrogen.In a mass-transfer binary one of the stars has filled its Roche lobe.,2018/7/20,,6,2018/7/20,,7,中等质量恒星的演化:与低质量恒星演化的主要区别,恒星内部H燃烧通过CNO循环进行，内部温度更高主序寿命更短。演化到RGB时间也非常短。He核不再是简并的，C和更重元素的燃烧平稳进行 核心区核反应产生能量主要以对流的方式向外传递外层氢和氦电离区存在脉动，多次穿过造父脉动代演化最终产物可能是碳氧白矮星或发生超新星爆发,2018/7/20,,8,简并条件,温度一定，密度越高越容易简并密度一定，温度越低越容易简并温度、密度一定，粒子质量越小越容易简并,系统中粒子的德布罗意波长大于等于粒子之间的平均距离：,相对论,非相对论,2018/7/20,,9,双星中的物质传输,星风传输：不相接、半相接双星大质量恒星在演化过程中通常有强烈的星风。 洛希瓣渗溢 ：半相接、相接双星形成吸积盘,
