致密星.pdf

第四章致密星 §4.1 白矮星 §4.2 中子星 §4.3 黑洞 What Are Compact Objects? Compact objects — white dwarfs, neutron stars, and black holes — are “born” when normal stars “die”, that is, when most of their nuclear fuel has been consumed. Since they do not burn nuclear fuel, the cannot support themselves against gravitational collapse by generating thermal pressure. The characteristic distinguishing compact objects from normal stars is their exceedingly small size. §4.1 白矮星(White Dwarfs) (20.3, 21.1, 21.3) 1. 发现 天狼星（Sirius ）双星，Porb= 50 yr m m 天狼A ：m = －1.45 ，M = 1.4 v v 天狼B：m = 8.68m ，M = 11.6m v v 4 轨道运动 Teff = 2.6 ×10 K 8 →M = 1.05 M →R ≈5 ×10 cm ⊙ 6 -3 ρ = 3.8 ×10 gcm Sirius in optical and X-ray Formation of white dwarfs A white dwarf is the product of a star with initial mass ~8-10 M . ⊙ After the star becomes a red giant, it will ejects its envelope as a planetary nebula, while the remains will shrink into a very compact core of carbon/oxygen, and that is white dwarf. V838 light echo 2. 白矮星基本特征 在H-R 图上白矮星位于主序带的左下方 球状星团M4 中的白矮星 光度与光谱： 绝对星等M ~ 8m-16m v 3 4 有效温度Teff ~ 5 ×10 - 4 ×10 K 光谱分类DC, DO, DB, DA, DF, DG, DM. Cooling of White Dwarfs There is no energy source in terms of fusion nor gravitational contraction, yet they shine. WD stars just continue to become coo