Gravity

In the Fall Semester, we look at the physics of gravitational motion and apply what we learn to a succession of gravitating systems with increasing numbers of bodies, at increasing distances from Earth: planets, binary stars, open and globular clusters of stars, galaxies, clusters of galaxies, and the Universe as a whole. We also look at the astronomer's tools: telescopes and their detectors.

Planetary Motion

5 lectures.

• Ancient perspectives. Kepler's empirical laws.
• Newtonian dynamics. Universal Law of Gravitation.
• Kepler problem. Planetary dynamics of the Solar System. Extrasolar planets.
• Tidal forces. Orbital resonances. Planetary rings. Asteroids. Comets.
• Special relativity. General relativity.
• Precession of perihelion of Mercury. Gravitational bending of light. Hulse-Taylor binary pulsar.

Binary Stars

2 lectures.

• Classification of binaries.
• Two-body Kepler problem. Tidal locking.
• Three-body Roche problem. Lagrange points. Mass transfer in binaries.

Star Clusters

3 lectures.

• Open clusters. Globular clusters.
• Virial theorem. Gravothermal catastrophe.
• Stellar collisions. Three-body interactions.
• Evolution of globular clusters. Dynamical friction. Evaporation. Core collapse.

Galactic Dynamics

7 lectures.

• Morphological classification of galaxies. Anatomy of the Milky Way. Stellar populations.
• Stellar orbits. Observation of proper motions in the Milky Way.
• Rotation curve. Central black hole.
• Mass-to-light ratio. Dark matter. MACHO experiment.
• Spiral galaxies. Winding problem. Density waves. Orbital resonances. Bars.
• Elliptical galaxies. Faber-Jackson Law and fundamental plane.
• Galaxy clusters. Mergers. Tidal stripping. Hot gas and cooling flows. Dark matter.

Expansion of the Universe

5 lectures.

• Cosmological redshifts. Hubble's Law. Ladder of distance scales.
• Measurement of Hubble's constant. HST Key Project. Gravitational lensing and quasar time delays. Water masers in NGC 4258. Peculiar motions and The Great Attractor.
• Newtonian cosmology. Relativistic cosmology. Age of the Universe. Fate of the Universe.
• Formation of large-scale structure. Filaments and voids. Galaxy-galaxy correlation function. Cold dark matter. Neutrinos.

Telescopes

3 lectures.

• Reflection. Refraction. Geometric optics. Classical telescope design.
• Diffraction. Interference. Telescope figures of merit.
• Modern optical telescopes. CCD detectors. Spectrographs. Adaptive optics.
• X-ray mirrors. X-ray detectors. X-ray satellites.
• Radio and optical interferometers. Very-long-baseline interferometry.

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