Physics Ladder · College

Astrophysics

The physics of the cosmos with calculus: magnitudes and spectra, binary stars and exoplanets, how stars shine and die, compact objects, galaxies, dark matter and cosmology.

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45 topics in 5 units. Builds on Astronomy and Waves, Optics and Modern Physics. Not sure this is the right course? Find your rung.

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Unit 1 Starlight

8 topics

Magnitudes and distances, dust, colors, the Planck function, and what spectral lines say about temperature.

  1. Magnitude Arithmetic
  2. Absolute Magnitude and the Distance Modulus
  3. Interstellar Dust: Extinction and Reddening
  4. Color Index and Temperature
  5. The Planck Function
  6. Effective Temperature and Stellar Radii
  7. Excitation and the Strength of Spectral Lines
  8. Ionization and the Spectral Sequence

Unit 2 Binary Stars and Exoplanets

6 topics

Masses from orbits, radial-velocity curves, eclipses and transits, and planet temperatures.

  1. Masses from Visual Binaries
  2. Spectroscopic Binaries
  3. Eclipsing Binaries
  4. Exoplanet Transits
  5. Exoplanet Masses from Wobbles
  6. Planet Temperatures and the Habitable Zone

Unit 3 How Stars Work

10 topics

Hydrostatic equilibrium, the virial theorem, fusion and tunneling, energy transport and the limits on stellar luminosity.

  1. Hydrostatic Equilibrium
  2. Estimating a Star's Center
  3. The Virial Theorem
  4. Gravity as a Power Source
  5. The Proton–Proton Chain and the CNO Cycle
  6. Why Fusion Needs Tunneling
  7. Radiation and Convection Inside Stars
  8. The Mass–Luminosity Relation
  9. The Eddington Luminosity
  10. Solar Neutrinos

Unit 4 Stellar Evolution and Compact Objects

12 topics

Evolutionary tracks, degenerate matter, white dwarfs and neutron stars, black holes, tides, accretion and gravitational waves.

  1. Evolutionary Tracks
  2. Electron Degeneracy Pressure
  3. The White Dwarf Mass–Radius Relation
  4. The Chandrasekhar Limit
  5. Core-Collapse Supernovae
  6. Neutron Stars
  7. Pulsar Spin-Down
  8. The Schwarzschild Radius
  9. Gravitational Redshift and Time Dilation
  10. Tidal Forces and the Roche Limit
  11. Accretion Power
  12. Gravitational Waves

Unit 5 Galaxies and Cosmology

9 topics

Rotation curves and dark matter, supermassive black holes, redshift and the scale factor, the Friedmann equation, the CMB and the first elements.

  1. Rotation Curves and Dark Matter
  2. Supermassive Black Holes
  3. The Cosmic Distance Ladder
  4. Redshift and the Scale Factor
  5. Hubble's Law in Practice
  6. The Friedmann Equation and Critical Density
  7. Matter, Radiation and Dark Energy Through Time
  8. The Cosmic Microwave Background
  9. Big Bang Nucleosynthesis
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