Final review study guide. ------------------------ *** Look at "Key Ideas" and "Key Equations" from every Lecture *** ---------------------------------------------------------------------- Light: Light as Waves and Photons Speed of Light Electromagnetic Spectrum Doppler Effect Spectroscopy: Kirchoff's Laws of Spectroscopy Blackbody Spectra Stefan-Boltzmann & Wien Laws Emission-Line Spectra Absorption-Line Spectra Matter and Gravity: Structure of Atoms Elements and Isotopes 4 Fundamental Forces (Strong & Weak Nuclear Forces Electromagnetic, & Gravitational Forces) Gravity: Inverse Square Law Newton's Version of Kepler's 3rd Law Circular and Escape Speeds Gravitational Binding Energy The Observed Properties of Stars -------------------------------- Stellar Distances: Trigonometric Parallaxes Units of distance: Parsec & Light Year Stellar Motions: Proper motions Radial velocity True Space Motion How these are measured and depend on distance Stellar Brightnesses: Luminosity Apparent Brightness Inverse Square Law of Brightness Stellar Spectra: Colors of stars and relation to Temperature Spectral Classification Spectral Sequence is a Temperature Sequence Main Spectral Types: O B A F G K M L T Stellar Masses & Radii: Types of Binary Stars (Visual, Spectroscopic, & Eclipsing) Use of binary stars for measuring masses Which types of binaries give the best masses How are stellar radii measured The Hertzsprung-Russell Diagram: Plot of Luminosity vs. Temperature for stars. Main Sequence Stars Giant Stars Supergiant Stars White Dwarfs Luminosity-Radius-Temperature Relation Luminosity Classification through spectral line widths Luminosity Classes Ia Ib II III IV and V Stellar Structure & Evolution ----------------------------- The Internal Structure of Stars: Mass-Luminosity Relationship Hydrostatic Equilibrium Core-Envelope Structure of Stars Energy Generation in the Sun: The Kelvin-Helmholtz Mechanism Nuclear Fusion Energy Proton-Proton Chain Lifetime of the Sun Solar Neutrinos The Main Sequence Burn Hydrogen into Helium in their cores. In Hydrostatic & Thermal Equilibrium Mass-Luminosity Relationship for M-S stars The Main Sequence is a Mass Sequence Lower M-S: M < 1.2 Msun Radiative cores & Convective envelopes Burn H via p-p chain Upper M-S: M > 1.2 Msun Convective cores & Radiative envelopes Burn H via CNO cycle Red Dwarfs: lowest mass M-S stars Fully convective Burn H via p-p chain Dependence of M-S Lifetime on stellar Mass. Larger Mass = Shorter Life. Typical lifetimes of O-stars, M-stars, & the Sun Minimum and Maximum masses of stars Brown Dwarfs (M < 0.08 Msun) The Evolution of Low Mass stars (M < 4 Msun) Main Sequence phase through H exhaustion in core He core formation & H shell burning Ascent of the Red Giant Branch Helium Flash & the Triple-Alpha Process Descent to the Horizontal Branch He core burning & H shell burning C-O core formation Asymptotic Giant Branch star He and H burning Shells Onset of instability Envelope Ejection & Formation of a Planetary Nebula Core evolves into a White Dwarf star What are the timescales for these phases? Stages of Evolution of High Mass O & B Stars (M > 4 Msun) Stars with 4 < M < 8 Msun Burn Hydrogen, then Helium, then Carbon Blow off their envelope after exhaustion of Carbin Burning Core becomes an O-Ne-Mg White Dwarf Stars with M > 8 Msun Burn Hydrogen up through Carbon, Neon, Oxygen & Silicon What are the timescales for these burning phases? Iron Core Formation & burning shells Catastrophic collapse of Iron Core leading to Iron core bounce & supernova explosion ejecting envelope core collapses to a neutron star or black hole Supernovae Nucleosynthesis in Supernovae (main source of heavy elements) Role of supernovae in seeding interstellar space with heavy elements Role of supernovae in producing neutron stars White Dwarfs: Remnant cores of low-mass stars (M < 8 Msun) Held up by Electron Degeneracy Pressure Different from the Ideal Gas Law Equation of State Maximum Mass ~1.4 Msun (Chandrasehkar Mass) White dwarf evolution into a "Black Dwarf" But, this takes a very long time. Neutron Stars: Remnant cores of massive stars (M > 8 Msun) Held up by Neutron Degeneracy Pressure Pulsar = rapidly spinning neutron star Model for a pulsar Pulsar evolution Neutron stars cannot support themselves above 2-3 Msun. Neutron degeneracy pressure fails. Gravity wins. Black Holes: Black Holes are totally collapsed objects gravity so strong not even light can escape predicted by General Relativity theory remnant cores of very massive stars (M > 25 Msun?) Schwarzschild Radius & Event Horizon: R_S = 2GM/c^2 Find them by their Gravity X-ray Binary Stars & Black Hole Candidates Hawking Radiation & Black Hole Evaporation Tests of Stellar Evolution: H-R Diagrams of Star Clusters Why clusters are good for testing stellar evolution Changes in the H-R diagram of a star cluster as it ages Estimating cluster ages from the Main-Sequence Turn-off Open Clusters Young clusters of few 100s - 1000s of stars Blue Main-Sequence stars & few giants Shapes of their H-R diagrams Range of ages from Few million to few billion years Globular Clusters Old clusters of a few 100,000 stars No blue Main-Sequence stars & many giants Shapes of their H-R diagrams 10-13 Billion years old The Milky Way Galaxy -------------------- The Milky Way is our Galaxy Diffuse band of light crossing the sky Galileo: Milky Way consists of many faint stars The Nature of the Milky Way Philosophical Speculations: Wright & Kant What is the geometry of the Milky Way? A spherical shell, or a disk? Size of the MW from Star Counts: Herschels Star Gauges Kapteyn Model Globular Cluster Distribution: Shapley, RR Lyrae stars First to locate the Sun outside the center of the Galaxy. The importance of dust obscuration in calculating the luminosity distance. Nature of the "Spiral Nebulae" ------------------------------ Two hypotheses: spiral nebulae are external, or internal to Milky Way? Island Universe Hypothesis (Kant & Humboldt) Nebular Hypothesis (Laplace) Role of finding distances in resolving the debate Leavitt: Cepheid Period-Luminosity Relation, distances Shapley-Curtis Debate (1920) Hubble: Cepheids in Andromeda The Milky Way & Andromeda ------------------------- Common Properties of the Milky Way & Andromeda Galaxies Disk & Spheroid Structure of the Galaxy Pop I Stars: Young, metal-rich, disk stars Ordered, nearly circular orbits in the disk Pop II Stars: Old, metal-poor, spheroid stars Disordered, elliptical orbits in all directions Chemical Evolution, connection to stellar populations Supermassive Blackholes Spiral Galaxies --------------- Disk & Spheroid Components Thick disk of stars, thin disk of dust, spiral arms Spheroid: bright central Bulge and faint extended Halo Rotation of the Disk Differential Rotation Pattern Orbital period of the Sun in the Galaxy Measurement of Galaxy Masses from Rotation Curve Spiral Arms: Outlined by O&B Stars, HII Regions, Gas & Dust clouds Spiral Density Waves in the Disk Sites of recent star formation. Why O&B stars don't move very far from their birthplaces. HI, HII, and H_2 gas. Types of Galaxies ----------------- Three basic types of Galaxies: Spirals Ellipticals Irregulars Dwarf Galaxies Differences between the types of galaxies in terms of Relative Gas content Star Formation History Internal Motions How galaxies evolve over time, collisions Groups & Clusters of Galaxies ----------------------------- Galaxies tend to group into Clusters The Milky Way is part of the Local Group Hierarchy of Structure: Groups: < 30 bright galaxies, many dwarfs Clusters: 30 - 100's of bright galaxies, many dwarfs Where Ellipticals & Spirals are found in Rich Clusters Superclusters: Clusters of Clusters Voids, Filaments, & Walls, porous structure of the universe Interacting Galaxies -------------------- Tidal Interactions occur between Galaxies Frequency of occurence Cause of most of the "peculiar" galaxies observed Tidal distortion in encounters Types of interactions Close Tidal Encounters Galaxy-Galaxy Collisions Splash encounters (Ring Galaxies) Starbursts induced by interactions Drive metal-rich super-winds into the Intergalactic medium Mergers & Galactic Cannibalism Active Galaxies & Quasars ------------------------- Found in a small fraction of all galaxies Compact source of energy in the nucleus Include the most luminous objects known Variability implies a limit on size. Types: Quasars: Quasi-stellar Radio Sources Radio Galaxies Power source: Supermassive Black Holes Accretion Disks Radio Jets Special Relativity: ------------------ First Postulate (uniformly moving observers) Second Postulate (speed of light) Newton's conception of absolute space & absolute time Einstein's conception of space & time as relative How time appears to different observers (the photon clock experiment) Special Relativity: ------------------ First Postulate (uniformly moving observers) Second Postulate (speed of light) Newton's conception of absolute space & absolute time Einstein's conception of space & time as relative How time appears to different observers (the photon clock experiment) General Relativity: ------------------ Shortest paths in curved spacetime Explanation of gravity as curved spacetime Matter tells spacetime how to curve, Curved spacetime tells matter how to move. Experimental verification of GR: Perihelion shift of Mercury Bending of Starlight near the Sun Strong gravitational lensing of galaxies by clusters Einstein's Cosmology: -------------------- Cosmological Principle: Universe is Homogeneous and Isotropic on Large Scales Cosmological Constant Evidence of large-scale homogeneity & isotropy Observational Cosmology: ----------------------- Hubble's Law Hubble Parameter, H0 How it is measured Uncertainties in measuring H0 Current rate of expansion of the Universe We are not at the center: raisins in expanding cake, points on expanding balloon, etc. Redshift distances Redshift maps Big Bang Theory: --------------- Basic features of the theory Expansion of the Universe (Hubble's Law) Density Parameter (Omega0) Critical Density Omega0 determines the geometry of the Universe Age of the Universe (Hubble Time) Primordial (Big Bang) Nucleosynthesis Production of Deuterium, Helium, and light metals (Li,Be,B) Predictions for observed abundances Comparison with predictions Cosmic Background Radiation Blackbody Spectrum & Temperature Observed properties Conditions at the Epoch of Recombination Earliest phases of the Universe Connection to particle physics Inflation Epoch - explains flatness & smoothness of the present Universe Predictions for observed properties in the present Universe Fate of the Universe The role of the density parameter in determining the expansion history of the Universe. How we measure the matter density: starlight, dark matter Evidence for an accelerating Universe (non-zero Cosmological Constant) Type Ia supernova results Future Evolution of an Open, Accelerating Universe Dark Matter ----------- Observational evidence for dark matter Rotation curves of galaxies Cluster lensing Galaxy dark matter halos Candidates for dark matter Contribution to budget of universe Dark Energy ----------- Vaccum energy of universe Role in accelerating expansion Dark energy types Contribution to budget of universe Time travel, General relativity, Wormholes ------------------------------------------ Wormholes: basic idea Granfather paradox Chronology Protection Conjecture Life in the Universe --------------------- Requirements for (intelligent?) life Drake Equation Fermi Paradox