Physics 172
Spring 2026

Stellar Astronomy & Cosmology 

Course Materials:

• Week 0: 1/21-23                  Intro to Astronomy [Ch. 1, 2]
  Physics 172 syllabus
  Wednesday, January 21: Lecture 1: Course structure, science & astronomy, units & notation.
  Wednesday, January 21: Lecture Notes: SI units, speed of light, light year.
  
  Friday, January 23: Lecture 2: Distances with c, scientific notation, length scales, Erastosthenes.
  Friday, January 23: Lecture Notes: Light years, exponents, and trigonometry.
  
  Problem Set #1, due Friday, January 30, 2026 (hard copy, due in-class)
  
  
  
• Week 1: 1/26-30                  Basic Physics I: Motion and Orbits [Ch. 2, 3]
  Monday, January 26: Class cancelled due to winter weather.
  
  Wednesday, January 28: Lecture 3: Orbital basics, seasons, parallax, Kepler's laws.
  
  Friday, January 30: Lecture 4: Constellations, Kepler's laws.
  Friday, January 30: Lecture Notes: Kepler's 2nd law and aphelion and perihelion.
  
  Problem Set #2 is due Friday, February 6 by 9:00 AM on ExpertTA.
  
  
  
• Week 2: 2/2-6                  Basic Physics II: Newton and Gravity [Ch. 3]
  Monday, February 2: Lecture 5: Galileo, gravity, Galilean relativity, and Newton's laws.
  Monday, February 2: Lecture Notes: Orbital speed vs orbital radius.
  Monday, February 2: Participation Exercise: Kepler's orbits and orbital capture.
  
  Wednesday, February 4: Lecture 6: Galilean relativity, Newton's laws, momentum and energy, gravity by Newton.
  Wednesday, February 4: Lecture Notes: Conservation of momentum, rifle recoil.
  
  Friday, February 6: Lecture 7: Newton's laws, circular motion, center of mass, angular momentum.
  Friday, February 6: Lecture Notes: Acceleration due to Earth's gravity.
  
  Problem Set #3 part 1 is due Friday, February 13 by 9:00 AM on ExpertTA.
  Problem Set #3 part 2 is due Friday, February 13 in class.
  
  
  
• Week 3: 2/9-13                  Basic Physics III: Light and Matter [Ch. 5, 16.1-2]
  Monday, February 9: Lecture 8: Potential energy, escape velocity, tidal forces, electromagnetic waves.
  Monday, February 9: Lecture Notes: Newton's version of Kepler's 3rd law for mass determination.
  
  Wednesday, February 11: Lecture 9: Electromagnetic spectrum, blackbody radiation, light pressure.
  Wednesday, February 11: Lecture Notes: Blackbody radiation of a hot star.
  
  Friday, February 13: Lecture 10: Blue sky, photons, atomic structure, spectroscopy, Doppler effect, nuclear particles.
  
  Problem Set #4 is due Wednesday, February 18 by 9:00 AM on ExpertTA.
  Extra practice problems for week 3 topics (ungraded)
  
  
  
• Week 4: 2/16-20                  Nuclear Physics & Astronomy Instruments [Ch. 5, 16.1-2, 6]
  Monday, February 16: Lecture 11: Doppler effect, Nuclear particles, P-P chain solar fusion, charged (anti-)particles.
  PowerPoint slides with videos [PPTX file, 75 MB]
  Monday, February 16: Lecture Notes: Doppler shift.
  
  Wednesday, February 18: Lecture 12: Nuclear particles, neutrinos, astrolabe, refracting and reflecting telescopes.
  Wednesday, February 18: Lecture Notes: Different types of ionizing radiation.
  
  MIDTERM #1 is scheduled for Friday, February 20, 2026 (in-class)
  Formula sheet for midterm #1
  
  
  
• Week 5: 2/23-27                  Astronomy Instruments [Ch. 16.1-2, 6]
  Monday, February 23: Lecture 13: Reflecting telescopes, angular resolution, adaptive optics.
  Monday, February 23: Lecture Notes: Angular resolution of the Gemini telescope.
  
  Wednesday, February 25: Lecture 14: Interlude 1, interferometry, CCD cameras, telescopes by wavelength.
  
  Friday, February 27: Lecture 15: CCD cameras, telescopes, The Sun (visual tour, surface, internal structure, fusion).
  Friday, February 27: Lecture Notes: Size of Betelgeuse.
  Optional: Ring of fire eclipse photo on APOD: LINK
  Optional: Ring of fire eclipse video on APOD: LINK
  
  Problem Set #5 part 1 is due Friday, March 6 by 9:00 AM on ExpertTA.
  Problem Set #5 part 2 is due Friday, March 6 in class.
  
  Interlude 1: Essay topics and instructions (due on Monday, March 23)
  Tentative Title Form (due on Monday, March 2)
  The Interlude 1 essay should be submitted as a PDF on Gradescope: PHYS 172 course on Gradescope
  
  
  
• Week 6: 3/2-6                  Our Sun & Main Sequence Stars [Ch. 15, 16, 17]
  Monday, March 2: Lecture 16: Surface of Sun, internal structure, solar fusion, Interlude 1 activity.
  
  Wednesday, March 4: Lecture 17: Star brightness, star color, star luminosity, stellar statistics, luminosity vs mass.
  Wednesday, March 4: Lecture Notes: Apparent brightness of Sirius versus Betelgeuse.
  Optional: Extremely zoomable center of the Milky Way galaxy (ESO, IR and near-IR): LINK
  
  Friday, March 6: Lecture 18: Luminosity vs mass, H-R diagram, stellar evolution, helium fusion, red giants.
  
  Problem Set #6 is due Wednesday, March 18 by 9:00 AM on ExpertTA.
  
  
  
• Week 7: 3/16-20                  White Dwarfs and Type II Supernovae [Ch. 22, 23]
  No class on Monday, March 16, due to inclement weather.
  
  Wednesday, March 18: Lecture 19: Sun-like stars: main sequence to red giant, planetary nebula, white dwarf.
  Wednesday, March 18: Lecture Notes: Pauli exclusion principle.
  Optional: Zoomable Helix nebula: Hubble and Kitt Peak (Noir Lab, very high resolution)
  
  Friday, March 20: Lecture 20: Evolution of massive stars, type-II supernovae (images & physics).
  Friday, March 20: Lecture Notes: Wavelength and luminosity of a just-born white dwarf.
  
  Problem Set #7 is due Monday, March 30 by 9:00 AM on ExpertTA.
  
  
  
• Week 8: 3/23-27                  Type II Supernovae, Neutron Stars, and Einstein's Relativity [22, 23, 24]
  Monday, March 23: Lecture 21: Type II supernova physics, supernovae remnants, origin of elements, neutron stars.
  Monday, March 23: Lecture Notes: Neutrino flux from supernova SN 1987A.
  Optional: Origin of the elements: Article in SCIENCE magazine (by J. A. Johnson, 2019)
  
  Wednesday, March 25: Lecture 22: Neutron stars, pulsars, special relativity, length contraction.
  Wednesday, March 25: Lecture Notes: Rotation frequency of a Sun-based white dwarf ... "neutron star".
  
  Friday, March 27: Lecture 23: Einstein, special relativity, length contraction, time dilation, general relativity.
  Optional: What if c=20 km/h ? Video simulation at captaineinstein.org, or on youtube.com
  
  Problem Set #8 is due Friday, April 3 by 9:00 AM on ExpertTA.
  
  MIDTERM #2 is scheduled for Monday, April 6, 2026 (in-class)
  Formula sheet for midterm #2
  
  
  
• Week 9: 3/30-3/4                  General Relativity, Black holes, and Exoplanets [24, 21]
  Monday, March 30: Lecture 24: General relativity, gravitational waves, and black holes.
  Monday, March 30: Lecture Notes: Time dilation for cosmic ray-generated muons.
  
  Wednesday, April 1: Lecture 25: Midterm #2 topics, gravitational waves, black holes, Roche limit.
  Wednesday, April 1: Lecture Notes: Size of the black hole at the center of the Milky Way galaxy.
  
  Friday, April 3: Lecture 26: Edge of a black hole, formation of a solar system, proto-planetary systems, exoplanets.
  Friday, April 3: Lecture Notes: Time dilation near a black hole.
  
  Extra practice problems on midterm #2 topics (ungraded)