Physics 016: The Course Notes, spring 2005. An important remark: the course notes are divided into sections and subsections, with titles as shown below. Please note that the division is meant to be logical, by topic. You should not necessarily assume that that one section of notes corresponds to exactly one lecture! The important thing is to read them sequentially, and to refer to the suggested readings in the textbook and elsewhere which are intended to parallel these discussions. Contents: 1. The Properties of the Sun 1.1: A Point-Form Summary 1.2: Associated Readings from the Text 1.3: The Sun's Luminosity 1.4: The Mass of the Sun 1.5: The Size and Density of the Sun 1.6: The Rotation of the Sun 1.7: The Interior Structure of the Sun 2. What Is The Sun Doing? 2.1: A Point-Form Summary 2.2: Associated Readings from the Text 2.3: The Sun's Behaviour: Two Possibilities 2.4: The Paradoxical Behaviour of the Sun 2.5: The Ultimate Fate 2.6: Is the Sun Slowly Shrinking? Kelvin Contraction 2.7: An Important Point About The Original Heat 2.8: Another Possible Heat Source: Chemical Reactions 3. An Introduction to Thermonuclear Fusion 3.1: A Point-Form Summary 3.2: Associated Readings from the Text 3.3: Energy from Mass 3.4: The Importance of Temperature 3.5: A Semantic Point 3.6: The Composition of the Sun 3.7: How Structurally Stable is the Sun? 3.8: A Mathematical Exercise 3.9: The Sun in Cross-Section 3.10: The States of Matter 3.11: A Brief Reminder of Atomic Structure 3.12: The Binding Energy Curve 3.13: The Sun: Not Exactly a Bomb 3.14: A Digression: The Atomic Bomb vs the Hydrogen Bomb 3.15: Back to Fusion in the Sun: The Proton-Proton Chain 3.16: How Do We Know All This? 3.17: The Positron and Its Uses 4. Probing the Deep Interior of the Sun 4.1: A Point-Form Summary 4.2: Associated Readings from the Text 4.3: Delayed at the Airport 4.4: Other PP Branches 4.5: The CNO Cycle 4.6: The Importance of Temperature, Revisited 4.7: Probing the Solar Interior: The Drunkard's Walk 4.8: Old News 4.9: Neutrinos Predicted: A Victory for Classical Physics 4.10: Neutrino Observatories: The First Attempts 4.11: Limitations on the Experiment 4.12: The Results 4.13: The Sudbury Neutrino Observatory: How It Works 5. The Sun in More Detail 5.1: A Point-Form Summary 5.2: Associated Readings from the Text 5.3: The Face of the Sun 5.4: Sunspots: Their Appearance and Phenomenology 5.5: Sunspots: Their Nature 5.6: Sunspots: The Patterns 5.7: Similar Behaviour in the Earth 5.8: The Earth-Sun Connection: A Scientific Case-Study 5.9: The Sunspot Connection: Some (Real?) Effects 5.10: Sunspots on Other Stars 5.11: GONG: Lessons from Seismology and Music 6. An Introduction to the Stars 6.1: A Point-Form Summary 6.2: Associated Readings from the Text 6.3: A Change of Scale 6.4: The Isolation of the Stars 6.5: What Would You Like to Know? 6.6: Even More Questions 6.7: In the Absence of... 6.8: Positions and Motions 6.9: The Motion of the Sun 6.10: The Apparent Brightnesses of the Stars 6.11: Colours, Temperatures - and Dust! 7. Stars and Their Distances 7.1: A Point-Form Summary 7.2: Associated Readings from the Text 7.3: Stellar Variability 7.4: Extrinsic Variables: Binary Stars 7.5: Intrinsic Variables 7.6: A Few Lines on a Chart 7.7: First Thoughts 7.8: Picking the Wrong Targets 7.9: Units of Distance Measurement 7.10: A Serendipitous Discovery 7.11: Increasing the Sample 7.12: What Can We Derive? 8. The HR Diagram 8.1: A Point-Form Summary 8.2: Associated Readings from the Text 8.3: A Search for Correlations 8.4: A Second Correlation 8.5: A Breakthrough in Understanding 9. Questions Arising from the HR Diagram 9.1: A Point-Form Summary 9.2: Associated Readings from the Text 9.3: Selection Effects: The Demographics of Stellar Populations 9.4: The Sun as a Representative Star 9.5: Telling Giants from Main Sequence Stars 9.6: Determining the Distances of Remote Stars by Spectroscopic Parallax 9.7: Do the Stars Change As Time Passes? 10. The Importance of Binary Stars 10.1: A Point-Form Summary 10.2: Associated Readings from the Text 10.3: Binary Stars Are Not Rare 10.4: Optical Doubles: Not Binaries! 10.5: Visual Binaries 10.6: Spectroscopic Binaries 10.7: Single-Lined Spectroscopic Binaries 10.8: Eclipsing Binaries 10.9: Astrometric Binaries 10.10: Final Remarks: Stellar Masses 11. Implications from Stellar Masses 11.1: A Point-Form Summary 11.2: Associated Readings from the Text 11.3: Stellar Masses 11.4: An Important Semantic Point 11.5: Do Stars Evolve Along the Main Sequence as They Age? 11.6: Why Should the Mass Matter So Much? 11.7: The Mass-Luminosity Law 11.8: The Main-Sequence Lifetimes of the Stars 12. Late in the Life of the Sun 12.1: A Point-Form Summary 12.2: Associated Readings from the Text 12.3: The Importance of Mass 12.4: Why These Lifetimes? 12.5: Slow Changes in the Core of the Star 12.6: The Behaviour of a Hypothetical Helium Star 12.7: Back to the Sun Itself 12.8: Defending the Fortress 12.9: What Does Helium Turn Into? The Triple-Alpha Process 12.10: How Will the Sun Look Late in Its Life? 12.11: How Do We Know This? The Difficulty 12.12: How Do We Know This? The Answer 13. The Importance of Star Clusters in Understanding Stellar Evolution 13.1: A Point-Form Summary 13.2: Associated Readings from the Text 13.3: The Use and Importance of Star Clusters 13.4: Are Star Clusters Real? 13.5: The Pace of Stellar Evolution 13.6: Remarks on Protostars 13.7: Imagine a Cluster in Formation 13.8: The Deaths of the Cluster Stars 13.9: Estimating Stellar Ages 13.10: The Turnoff Age 13.11: Not Only Red Giants! 13.12: The Practical Realities 13.13: Some Real Clusters 13.14: A Real Research Example 13.15: The Crowded Confines of a Star Cluster 13.16: Is the Sun in a Cluster at Present? 13.17: Was the Sun Ever in a Cluster? 13.18: The Kinds of Clusters 14. The Chandrasekhar Limit 14.1: A Point-Form Summary 14.2: Associated Readings from the Text 14.3: Your Expectations 14.4: The Importance of Quantum Mechanical Effects 14.5: Electron Degeneracy: The Exclusion Principle 14.6: In the Core of the Sun 14.7: The Story of Chandrasekhar 14.8: Chandra's Earliest Work: The Chandrasekhar Limit 14.9: Chandra's Later Contributions 14.10: Twinkle, Twinkle 14.11: The Diamond Exposed 14.12: Planetary Nebulae 14.13: Why Does the Star Shed Its Skin? 14.14: A White Dwarf Forever 15. Supernovae: The Deaths of Massive Stars 15.1: A Point-Form Summary 15.2: Associated Readings from the Text 15.3: A Quick Review of the Low-Mass Stars 15.4: More Massive Stars: Onion-Skin Models 15.5: The Odd-Even Effect Explained 15.6: Iron Stars: The End of It All 15.7: What Now? Some Thoughts 15.8: Neutron Degeneracy: Neutron Stars Predicted 15.9: Forming Neutron Stars 15.10: Perfect Billiard Balls 15.11: Supernovae: The Fireworks That Go With Neutron Star Birth 15.12: Other Components of the Supernova 15.13: Forming Even Heavier Elements; Enriching the ISM 15.14: A Case Study of a Supernova: 1987A 15.15: The Detectability of Neutron Stars 16. Pulsars 16.1: A Point-Form Summary 16.2: Associated Readings from the Text 16.3: The Discovery of Pulsars 16.4: A Sad Corollary 16.5: Pulsars as Lighthouses 16.6: Cyclotrons 16.7: A Complication: The Synchrotron 16.8: Synchrotron Radiation 16.9: The Oblique Rotator 16.10: Pulsars: The Beacon Observed 16.11: Pulsar Slowdown 16.12: Pulsar Spin-Up 16.13: The Crab Nebula: An Ancient Supernova 16.14: The Crab Nebula: The Connection Proven 17. Novae 17.1: A Point-Form Summary 17.2: Associated Readings from the Text 17.3: Back to Binary Stars 17.4: Degrees of Connectedness 17.5: Mass Exchange and Its Inevitability 17.6: The Details: Slow Accumulation 17.7: The Effect of the Infall on Ordinary Stars 17.8: Back and Forth 17.9: Fuel Onto the Fire 17.10: Novae Observed 17.11: But Not the Sun 17.12: One More Kind of Supernova 18. An Introduction to Black Holes 18.1: A Point-Form Summary 18.2: Associated Readings from the Text 18.3: The Inevitability of Black Holes: An Introduction to Relativity 18.4: What Relativity Means: The Strange Behaviour of Light 18.5: Why Einsteinian Relativity `Works' the Way It Does 18.6: Time Dilatation 18.7: A Helpful Visualisation 19. Gravity as Geometry 19.1: A Point-Form Summary 19.2: Associated Readings from the Text 19.3: A Fresh Look at Gravity 19.4: Light Itself 19.5: The Bending of Starlight by the Sun 19.6: The Anomalous Precession of Mercury's Orbit 19.7: Look at All Those Fish! Gravitational Lensing 19.8: Gravitational Redshift 19.9: Making a Strong Gravitational Field 19.10: Black Holes Foreseen 19.11: Are Black Holes Really Inevitable? 19.12: Light Near a Black Hole 19.13: The Schwarzschild Radius 19.14: Not Really Vanished 20. Finishing Off Black Holes 20.1: A Point-Form Summary 20.2: Associated Readings from the Text 20.3: Exploring a Black Hole 20.4: Searching for Black Holes 20.5: Not a General Inflow 20.6: Gravitational Focussing: MACHO 20.7: Black Hole Binaries 20.8: Supermassive Black Holes 20.9: The Fate of Black Holes 21. Star Formation 21.1: A Point-Form Summary 21.2: Associated Readings from the Text 21.3: Stellar Nurseries 21.4: Signposts of Star Formation 21.5: The Orion Nebula 21.6: Putting It All Together: The Full Cycle 22. Dust in the Interstellar Medium 22.1: A Point-Form Summary 22.2: Associated Readings from the Text 22.3: The General Interstellar Medium (ISM) 22.4: How Might Interstellar Material Make Its Presence Known? 22.5: Dust: The Dimming of the Stars 22.6: Why is the Sky Blue? 22.7: Expectations for the ISM - and the Reality 22.8: The Interstellar Reddening 22.9: Correcting for the Effects of Interstellar Dust 22.10: Dust in Dark Clouds 22.11: Dust in Reflection Nebulae 22.12: Direct Samples? No Way 22.13: Shapes and Orientations: The Polarization of Light 22.14: Controlling the Grains: What Doesn't Work 22.15: Controlling the Grains: What Does Work 22.16: The Composition of the Grains 23. Gas in the ISM 23.1: A Point-Form Summary 23.2: Associated Readings from the Text 23.3: So Much For Dust: How About the Gas? 23.4: Gas in Cool Clouds: Absorption 23.5: Gas in Hot Clouds: Emission 23.6: New Instruments Yield New Insights 23.7: Radio Telescopes: The 21-cm Radiation of Neutral Hydrogen 23.8: Infrared Detectors: Star Formation 23.9: Millimeter-wave Detectors: Interstellar Molecules Again 24. The Size and Shape of Our Galaxy 24.1: A Point-Form Summary 24.2: Associated Readings from the Text 24.3: Observable Features and Obvious Questions 24.4: Our Place in the Milky Way 24.5: A Serious Objection 24.6: Herschel's Star Counts 24.7: The Kapteyn Universe 24.8: Shapley and the Globulars 24.9: The Flattening of the Milky Way 24.10: The Structure of the Milky Way 24.11: When and How Did the Milky Way Form? 24.12: The Motions of the Globular Clusters 24.13: Summary 25. The Discovery of External Galaxies 25.1: A Point-Form Summary 25.2: Associated Readings from the Text 25.3: What Are They? 25.4: Cepheid Variables 25.5: What Are Cepheids Doing, and Why? 25.6: The Period-Luminosity Relationship 25.7: Determining Distances with Cepheids: Mixed Blessings 25.8: The Great Debate 25.9: Shapley versus Hubble 26. Galaxies of All Kinds 26.1: A Point-Form Summary 26.2: Associated Readings from the Text 26.3: Spreading the Net 26.4: Hubble's Tuning Fork 26.5: Evolution? What's the Evidence? 26.6: The Masses of Galaxies: Dark Matter 26.7: Galaxy Interactions 26.8: The Cross-Sections of Galaxies 26.9: Mergers 26.10: The Distribution of Galaxies: Conurbations 26.11: One Big Difference 26.12: The Local Group 26.13: Nearby Clusters 26.14: Larger-Scale Structure 27. The Expanding Universe 27.1: A Point-Form Summary 27.2: Associated Readings from the Text 27.3: Hubble's Discovery 27.4: The Cosmological Principle 27.5: Uniform Expansion 27.6: Opportunities Missed 27.7: Olbers' Paradox 27.8: Einstein's Missed Opportunity 27.9: Hubble Anticipated 27.10: Einstein's Solution 28. Quasars and Active Galaxies 28.1: A Point-Form Summary 28.2: Associated Readings from the Text 28.3: The Interpretation of Redshift 28.4: Radio Sources 28.5: Enter the Moon 28.6: Back to Astrophysics 28.7: Maarten Schmidt's Discovery 28.8: ...and the Problem 28.9: No Lack of Imagination 28.10: Some Simple Predictions 28.11: A Growing Understanding 29. The Hot Big Bang 29.1: A Point-Form Summary 29.2: Associated Readings from the Text 29.3: The `Expansion Age' of the Universe 29.4: Hubble's Answer 29.5: Why Not the Big Bang? 29.6: Gamow's Speculations 29.7: Interest Lost and Regained 29.8: Serendipity Again 29.9: Let There Be Light 30. The Geometry of the Universe 30.1: A Point-Form Summary 30.2: Associated Readings from the Text 30.3: No Centre 30.4: An Infinite Universe 30.5: A Finite Universe 30.6: Curvature in the Universe 30.7: Measuring the Curvature of a Globe 30.8: Measuring the Curvature of the Universe 30.9: How Mass Determines the Geometry and the Fate of the Universe 30.10: Measure the Local Density 30.11: Measure the Slowdown 30.12: The Likely Future 30.13: Why We Believe in the Big Bang 31. Closing Thoughts 31.1: A Point-Form Summary 31.2: Associated Readings from the Text 31.3: Motivation 31.4: The Present Structure 31.5: The Growth of Structure 31.6: Why So Uniform? 31.7: Inflation 31.8: Back to the Future 31.9: Supernovae 31.10: The Surprising Result 31.11: Absolutely Final Remarks

Textbook: General Remarks.

The textbook in this course is The Cosmic Perspective (Third edition), by Bennett, Donahue, Schneider and Voit. It is published by Pearson: Addison Wesley and is available in the Campus Bookstore. I would encourage you to buy a copy if you can, since it contains a couple of shrink-wrapped CDs which are very helpful. They have exercises, links to the publisher's website, self-test modules, beautiful and informative simulations and figures, and so on. As we progress, I will be advising you what you should be reading. One point I want to emphasise is that my course notes, which should also be read, do not parallel the discussion in the text, and I may from time to time be advising you to read a section in an unexpected location (like in a Chapter very near the end of the text). Such instructions are not mistakes! Finally, I should note that there are some topics which are covered very nicely in the text and which I will therefore not spend a lot of time rehashing in the lectures or in my course notes. The general rule is this: if I advise you to be familiar with a particular section of the text, you should take that not merely as a suggestion but rather as an assigned reading for which you are responsible. You may expect to be asked questions on that material on the tests and examinations. Next chapter

0: Physics 016: The Course Notes, spring 2005. 1: The Properties of the Sun: 2: What Is The Sun Doing? 3: An Introduction to Thermonuclear Fusion. 4: Probing the Deep Interior of the Sun. 5: The Sun in More Detail. 6: An Introduction to the Stars. 7: Stars and Their Distances: 8: The HR Diagram: 9: Questions Arising from the HR Diagram: 10: The Importance of Binary Stars: 11: Implications from Stellar Masses: 12: Late in the Life of the Sun: 13: The Importance of Star Clusters in Understanding Stellar Evolution: 14: The Chandrasekhar Limit: 15: Supernovae: The Deaths of Massive Stars, 16: Pulsars: 17: Novae: 18: An Introduction to Black Holes: 19: Gravity as Geometry: 20: Finishing Off Black Holes: 21: Star Formation: 22: Dust in the Interstellar Medium: 23: Gas in the ISM: 24: The Size and Shape of Our Galaxy: 25: The Discovery of External Galaxies: 26: Galaxies of All Kinds: 27: The Expanding Universe: 28: Quasars and Active Galaxies: 29: The Hot Big Bang: 30: The Geometry of the Universe: 31: Closing Thoughts:

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