ASTRONOMY 2    Spring 2007 Review Topics

 

I History.

            A. Greek astronomy.

                        1. Concepts of the celestial sphere- poles and equator - rotates once per day.

                        2. SunÕs motion defines ecliptic.

                        3. Wandering stars called planets. Problem of retrograde motion.

                        4. Geocentric model of solar system, epicycles.

                        5. Arguments for a spherical earth.

                        6. Explanations for moonÕs phases, eclipses.

                        7. Size of earth measured.

                        8. Precession.

            B. Copernicus and later.

                        1. Copernicus.

                                    a. Proposed heliocentric system.

                                    b. Siderial periods, distances of the planets from sun..

2. Tycho Brahe.

                                    a. Obtained many observations of positions of planets.

                                    b. Attempted to measure parallaxes of a Ōnew starĶ, comet.

                        3.Kepler.

                                    a. Three laws of planetary motion.

                                    b. Properties of ellipses- major axis, focus, eccentricity.

                        4. Galileo.

                                    a. Mechanics: law of falling bodies, uniform acceleration, inertia.

                                    b. Astronomical observations: moons of Jupiter, phases of Venus, rough surface of the

                                        moon, sunspots, many faint stars invisible to naked eye.

                        5. Huygens: acceleration in circular motion, scalars, vectors.

                        6. Newton.

                                    a. Concepts of mass, force.

                                    b. Three laws of motion.

                                    c. Law of gravity.

                                    d. Improved KeplerÕs Third Law.

                                    e. Tides.

                        7. Neptune discovered because of its gravitational effects.

                        8. First stellar parallax measured in 1838.

 

II. Physics of light and atoms.

            A. Light: Propagates in straight lines, speed a constant in vacuum, inverse square law, wave

                           properties- wavelength and frequency- diffraction, reflection, refraction, Doppler effect,

                           full electromagnetic spectrum, photons, energy per photon.

            B. Spectroscopy: KirchoffÕs three laws, black body spectrum, WienÕs law, Stephan-Boltzmann law.

            C. Atomic spectra: atomic structure, nucleus of protons, electrons, concept of charge and electric

                                          force, atomic mass and number, isotopes, electron orbits, energy levels,

                                          excitation, various types of transitions, production and absorption of photons,

                                          ionization, recombination.

 

III. Stars.

            A. Hertzsprung-Russell diagram: magnitudes- apparent and absolute- trigonometric parallaxes,

                 parsec, spectral types, colors of stars, temperatures of stars, luminosity classification,

                 main sequence, dwarfs, red giants, supergiants, white dwarfs, method of spectroscopic distances.

            B. Properties of stars: luminosity depends on temperature and radius, masses from binary stars,

                                                abundances of the elements from absorption lines, mass-luminosity relationship.

            C. Clusters of stars: use to calibrate H-R diagram.

            D. Internal structure of stars.

                        1. Basic physics: gas pressure law, equations of thermal equilibrium, modes of

                              of energy transport, energy generation mechanisms.

                                    a. Hydrostatic equilibrium.

                                    b. Energy transport usually by radiation or convection.

                                    c. Energy generation by nuclear reactions most of time, by gravitational contraction

                                        in transition phases (Kelvin-Helmholtz mechanism).

                        2. Basic equation to solve for structure: equations of hydrostatic equilibrium, energy

                              transport, energy generation, and density distribution as  functions of radius.

            E. Results of interior calculations: Upper main sequence stars, lower main sequence stars, hydrogen

                  burning

            F. Stellar evolution.

                        1. Main sequence lifetime depends on mass, luminosity.

                        2. Giants, supergiants, transition phases understood.

                        3. He, C, O, etc. burning.

                        4.Endpoints (depends on mass): supernovae (leave behind black hole, neutron star),

                            planetary nebula, white dwarfs, chemical enrichment of interstellar medium.

                        5. Variable stars: Cepheid variables.

            G. Star formation: result of gravitational collapse, fragmentation, collapse leading to nuclear burning.

            H. H-R diagrams for clusters, age dating of clusters.

 

IV. Our galaxy.

            A. Basic contents and structure: stars, star clusters, interstellar gas and dust, older stars in halo,

                 young stars and gas, dust in flattened disk.

            B. Rotation, persistence of spiral arms, mass.

            C. History: collapse, chemical enrichment.

 

V. External galaxies.

            A. Curtis-Shapley debate.

            B. Distance determinations to nearby galaxies.

            C. Distance determinations to more distant galaxies.

            D. Types of galaxies, formation of galaxies.

            E. Radio galaxies, quasars.

            F. Clusters of galaxies.

            G. Evidence for an expanding universe.

 

VI. Cosmology.

            A. The velocity -distance relationship, the Hubble constant and its determination.

            B. The cosmological principle.

            C. Big-bang and steady state theories.

            D. The cosmic microwave background.

            E. The early universe, galaxy formation.

            F. The fate of the universe: deceleration parameter, mean density, dark matter, dark energy.