Astronomy

Astronomy is the scientific study of celestial objects, space, and the universe as a whole. Astrophysics is a branch of astronomy that applies the principles of physics and chemistry to understand how stars, galaxies, and the universe evolve.

Virtually all of the concepts we have learned in relativity and quantum field theory can be applied to astrophysics. Newtonian mechanics describes the motion of planets and other celestial objects. Studies of particle physics and high-energy physics are essential for understanding phenomena such as cosmic rays, black holes, and the early universe. Condensed matter physics is crucial for understanding the properties of matter in extreme environments, such as neutron stars and white dwarfs. Nuclear physics tells us about the processes that power stars and the synthesis of elements in the universe. Thermodynamics and statistical mechanics are universally applicable, as they describe the behavior of matter and energy in various astrophysical systems. Even chemistry is important for understanding the composition of stars and planets, as well as the formation of molecules in space. Recently, for example, astrochemistry has become instrumental in the studies of abiogenesis.

For this section, we will follow Carroll and Ostlie's "An Introduction to Modern Astrophysics" as a reference. I will obviously include other sources as well, but this is a great general textbook that covers a wide range of topics in astrophysics.

Assumed knowledge includes classical (Newtonian, perhaps some Lagrangian and Hamiltonian) mechanics, electromagnetism, special and general relativity, as well as quantum mechanics. These are all topics I have written notes on, which is why I do not plan to cover them in detail here. Some knowledge of statistical mechanics, thermodynamics, and nuclear physics is also helpful, but as these are not topics I have written notes on, I will try to include some background information as needed.

The Structure of the Notes

This is just a plan as it is written prior to writing the actual notes. I will likely adjust the structure as I go along.

1. History of Astronomy: A brief overview of the history of astronomy, from ancient times to modern day.
   • Ancient Greek astronomy (Ptolemy, Copernicus et al.)
   • The scientific revolution (Galileo, Kepler, Newton et al.)
   • Spectroscopy and the birth of astrophysics (Herschel, Fraunhofer, Huggins, Planck et al.)
   • Birth of quantum mechanics and relativity (Einstein, Bohr, Heisenberg, Schrödinger et al.)
   • Modern astronomy (Hubble, Hawking, etc.)
2. Introduction fo Stars: Basic properties of stars, including their formation, structure, and evolution.
   • Binary star systems
   • Classification of stars (Hertzsprung-Russell diagram)
   • Hydrostatic equilibrium within stars
   • Stellar evolution (interstellar medium, protostars, main sequence, red giants, white dwarfs, supernovae, neutron stars, black holes)
   • Stellar pulsations and variable stars
3. Planetary Systems: An overview of planetary systems.
   • Formation of planetary systems (protoplanetary disks, accretion)
   • Types of planets (terrestrial, gas giants, ice giants)
   • Other minor bodies (asteroids, comets, Kuiper belt, Oort cloud)
   • Exoplanets and methods of detection (transit method, radial velocity method, direct imaging)
4. Galaxies: An overview of galaxies, including their types, structure, and evolution.
   • Classification of galaxies (Hubble sequence)
   • Galactic evolution (mergers, interactions)
   • Active galactic nuclei and quasars
   • Dark matter and dark energy
5. Cosmology: An overview of the universe as a whole, including its origin, structure, and evolution.
   • General relativity (differential geometry, field equations, the various metric solutions)
   • The expanding universe (Hubble's law, redshift, cosmic microwave background)
   • Observational cosmology (large scale structure, galaxy surveys, galaxy clusters)
   • The early universe (Big Bang, nucleosynthesis, inflation)