5: Theory of Stellar Evolution
- Page ID
- 141621
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 5.1: Introduction
- This page covers stellar evolution, noting that over 90% of a star's life is well understood, despite challenges in the early and late phases due to limited data. It emphasizes the study of "normal stars" and the use of polytropic models to illustrate their evolution. Calculations are key to uncovering details such as lifetimes, with the Hertzsprung-Russell diagram serving as a tool to explore stellar internal structure.
- 5.2: The Ranges of Stellar Masses, Radii, and Luminosity
- This page explores the dynamics of stellar mass, radiation pressure, and stability in stars. It highlights that higher mass stars (above 100M⊙) struggle with instabilities and mass loss due to radiation pressure, while stars require a minimum mass of around 0.1M⊙ for nuclear fusion.
- 5.3: Evolution onto the Main Sequence
- This page explores the intricacies of star formation, highlighting opposing forces to gravitational contraction and the Jeans length concept for gas cloud instability. It details protostar evolution, emphasizing gravitational density and collapse dynamics. The connection between effective temperature, radiative opacity, and stellar evolution on the Hertzsprung-Russell diagram is discussed, along with the Virial theorem's impact on luminosity as stars contract towards the main sequence.
- 5.4: The Structure and Evolution of Main Sequence Stars
- This page covers the life stages of stars, emphasizing their main sequence phase where stars achieve stability through hydrogen fusion. Lower mass stars use the proton-proton cycle, while those over 2 solar masses utilize the CNO cycle, leading to distinct structural characteristics. As hydrogen fuel diminishes, slight temperature increases and changes help compensate until significant transformations occur after most mass converts to helium, marking the star's transition from the main sequence.
- 5.5: Post Main Sequence Evolution
- This page covers the evolution of stars after the main sequence, focusing on low and high-mass stars. It details how lower main sequence stars develop helium cores and transition to red giants, culminating in white dwarfs after a helium flash. Massive stars undergo significant changes, potentially leading to supernovae, influenced by mass loss from stellar winds.
- 5.6: Summary and Recapitulation
- This page details the lifecycle of normal stars, covering their evolution from formation to eventual fate, and highlights key areas of stellar evolution such as nucleosynthesis, binary star evolution, and effects of mass loss. It discusses the evolutionary path of a 5M⊙ star, focusing on hydrogen and carbon burning stages while connecting theoretical models to observable clusters on the H-R diagram.
- 5.7: Problems
- This page explores stellar evolution, highlighting energy generation in sun-like stars and their behaviors. It details methods for determining mass fractions affecting energy production and compares fusion cycle contributions across various star masses.
- 5.8: References and Supplemental Reading
- This page provides a comprehensive overview of key literature and reviews on stellar evolution, centering on protostars, stellar structure, and white dwarf theories. It features influential authors like Hayashi and Iben Jr. and discusses traditional and modern viewpoints on protostar collapse, hydrodynamic challenges in stellar contraction, and empirical findings on star masses and evolution.