Physics 172
Spring 2025

Stellar Astronomy & Cosmology 

Course Materials:

• Week 0: 1/22-24                  Intro to Astronomy [Ch. 1, 2]
  Physics 172 syllabus
  Wednesday, January 22: Class cancelled due to winter weather.
  Friday, January 24: Lecture 1: Course structure, science & astronomy, units & notation.
  Friday, January 24: Lecture Notes: SI units, speed of light, light year.
  
  Problem Set #1, due Friday, January 31, 2025 (hard copy, due in-class)
  
  
  
• Week 1: 1/27-31                  Basic Physics I: Motion and Orbits [Ch. 2, 3]
  Monday, January 27: Lecture 2: Distances with c, scientific notation, length scales, Erastostenes.
  Monday, January 27: Lecture Notes: Light years, exponents, and trigonometry review.
  
  Wednesday, January 29: Lecture 3: Orbital basics, seasons, parallax, Kepler's laws.
  
  Friday, January 31: Lecture 4: Constellations, Kepler's laws.
  Friday, January 31: Lecture Notes: Kepler's 2nd law at aphelion and perihelion.
  
  Problem Set #2 is due Friday, February 7 by 9:00 AM on ExpertTA.
  
  
  
• Week 2: 2/3-7                  Basic Physics II: Newton and Gravity [Ch. 3]
  Monday, February 3: Lecture 5: Galileo, gravity, Galilean relativity, and Newton's laws.
  Monday, February 3: Lecture Notes, Problem #1: Kepler's 2nd law at aphelion and perihelion (continued).
  Monday, February 3: Lecture Notes, Problem #2: Orbital speed vs orbital radius.
  
  Wednesday, February 5: Lecture 6: Galilean relativity, Newton's laws, momentum and energy, gravity by Newton.
  Wednesday, February 5: Lecture Notes: Conservation of momentum, rifle recoil.
  
  Friday, February 7: Lecture 7: Newton's laws, circular motion, center of mass, angular momentum.
  Friday, February 7: Lecture Notes: Acceleration due to Earth's gravity.
  
  Problem Set #3 is due Friday, February 14 by 9:00 AM on ExpertTA.
  Extra practice problems for week 2 topics (ungraded)
  
  
  
• Week 3: 2/10-14                  Basic Physics III: Light and Matter [Ch. 5, 16.1-2]
  Monday, February 10: Lecture 8: Escape velocity, tidal forces, electromagnetic waves.
  Monday, February 10: Lecture Notes: Newton's version of Kepler's 3rd law for mass determination.
  
  Wednesday, February 12: Lecture 9: Electromagnetic spectrum, blackbody radiation, light pressure.
  Wednesday, February 12: Lecture Notes: Blackbody radiation of a hot star.
  
  Friday, February 14: Lecture 10: Photons, atomic structure, spectroscopy, Doppler effect, nuclear particles.
  
  Problem Set #4 is due Wednesday, February 19 by 9:00 AM on ExpertTA.
  Extra practice problems for week 3 topics (ungraded)
  
  
  
• Week 4: 2/17-21                  Nuclear Physics & Astronomy Instruments [Ch. 5, 16.1-2, 6]
  Monday, February 17: Lecture 11: Doppler effect, Nuclear particles, P-P chain solar fusion, charged (anti-)particles.
  Monday, February 17: Lecture Notes: Doppler shift.
  
  Wednesday, February 19: class cancelled due to winter weather.
  
  Friday, February 21: class cancelled due to winter weather.
  
  MIDTERM #1 (originally on Friday, Feb. 21) is scheduled for Monday, February 24, 2025 (in-class)
  Formula sheet for midterm #1
  
  
  
• Week 5: 2/24-28                  Astronomy Instruments [16.1-2, 6]
  MIDTERM #1 on Monday, February 24 (in-class)
  Formula sheet for midterm #1
  
  Wednesday, February 26: Lecture 12: nuclear particles vs photons, astrolabe, refracting and reflecting telescopes.
  
  Friday, February 28: Lecture 13: Reflecting telescopes, angular resolution, adaptive optics.
  Friday, February 28: Lecture Notes: Angular resolution of the Gemini telescope.
  
  Problem Set #5 is due Friday, March 7 by 9:00 AM on ExpertTA.
  
  
  
• Week 6: 3/3-7                  Our Sun & Main Sequence Stars [6, 15, 16, 17]
  Monday, March 3: Lecture 14: Angular resolution, interferometry, CCD cameras, telescopes by wavelength.
  Monday, March 3: Lecture Notes: Size of Betelgeuse.
  
  Wednesday, March 5: Lecture 15: The Sun (visual tour, surface, internal structure, solar fusion).
  Optional: Ring of fire eclipse photo on APOD: LINK
  Optional: Ring of fire eclipse video on APOD: LINK
  
  Friday, March 7: Lecture 16: Interlude 1 instructions, star brightness, star color, star luminosity.
  Friday, March 7: Lecture Notes: Apparent brightness of Sirius versus Betelgeuse.
  
  Problem Set #6 is due Friday, March 21 by 9:00 AM on ExpertTA.
  
  Interlude 1: Essay topics and instructions (due on Friday, March 28)
  Tentative Title Form (due on Monday, March 17)
  The Interlude 1 essay should be submitted as a PDF on Gradescope: PHYS 172 course on Gradescope
  
  
  
• Week 7: 3/17-21                  Main Sequence Stars [18, 19, 22, 23]
  Monday, March 17: Lecture 17: Stellar statistics, luminosity vs mass, H-R diagram, stellar evolution.
  Optional: Extremely zoomable center of the Milky Way galaxy (ESO, IR and near-IR): LINK
  
  Wednesday, March 19: Lecture 18: Sun-like stars: main sequence to red giant, planetary nebula, white dwarf.
  Wednesday, March 19: Lecture Notes: Pauli exclusion principle.
  Optional: Zoomable Helix nebula: Hubble and Kitt Peak (Noir Lab, very high resolution)
  
  Friday, March 21: Lecture 19: Evolution of massive stars, type-II supernovae (images & physics).
  Friday, March 21: Lecture Notes: Wavelength and luminosity of a just-born white dwarf.
  
  
  
• Week 8: 3/24-28                  Type II Supernovae and Einstein's Relativity [22, 23, 24]
  Monday, March 24: Lecture 20: Type II supernova physics, supernovae remnants, neutron stars, pulsars.
  Monday, March 24: Lecture Notes: Neutrino flux from supernova SN 1987A.
  
  Wednesday, March 26: Lecture 21: Neutron stars, pulsars, special relativity, length contraction.
  Wednesday, March 26: Lecture Notes: Rotation frequency of a Sun-based white dwarf ... "neutron star".
  
  Friday, March 26: Lecture 22: 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 #7 is due Friday, April 4 by 9:00 AM on ExpertTA.
  
  MIDTERM #2 is scheduled for Monday, April 7, 2025 (in-class)
  Formula sheet for midterm #2
  
  
  
• Week 9: 3/31-4/4                  General Relativity, Black holes, and Exoplanets [24, 21]
  Monday, March 31: Lecture 23: General relativity, gravitational waves, and black holes.
  Monday, March 31: Lecture Notes: Time dilation for cosmic ray-generated muons.
  
  Wednesday, April 2: Lecture 24: Midterm #2 topics, gravitational waves, black holes, Roche limit.
  Wednesday, April 2: Lecture Notes: Size of the black hole at the center of the Milky Way galaxy.
  Optional: What do you see as you fall into a black hole ? Explainer and a shorter virtual reality version
  
  Friday, April 4: Lecture 25: Formation of a solar system, proto-planetary systems, exoplanets.
  Friday, April 4: Lecture Notes: Time dilation near a black hole.
  
  Extra practice problems (ungraded)
  
  Problem Set #8 is due Friday, April 11 by 9:00 AM on ExpertTA.
  
  
  
• Week 10: 4/7-11                  Exoplanets and the Milky Way Galaxy [7, 14.3-4, 30.1-3, 25]
  MIDTERM #2 on Monday, April 7 (in-class)
  Formula sheet for midterm #2
  
  Wednesday, April 9: Lecture 26: Protoplanetary systems, exoplanets, exolife possibilities.
  
  Friday, April 11: Lecture 27: Milky Way galaxy, galaxy structure, galaxy formation.
  Friday, April 11: Lecture Notes: Detecting human radiowaves on Alpha-Centauri.
  
  Problem Set #9 is due Friday, April 18 by 9:00 AM on ExpertTA.
  
  
  
• Week 11: 4/14-18                  Galaxy Types and Structures [25, 26, 27]
  Monday, April 14: Lecture 28: Interlude 2 instructions, "Great Debate", rotation curve, spiral galaxy formation.
  Monday, April 14: Lecture Notes: Estimating the mass of the Milky Way galaxy inside the Sun's orbit.
  
  Interlude 2: Essay topics and instructions (due on Monday, April 28)
  The Interlude 1 essay should be submitted as a PDF on Gradescope: PHYS 172 course on Gradescope
  The readings for this "Great Debate" interlude are located on the Blackboard course site.
  
  Wednesday, April 16: Lecture 29: Dark matter, formation of the Milky Way galaxy.
  Wednesday, April 16: Lecture Notes: Estimating the mass of the Milky Way galaxy using its rotation curve.
  
  Friday, April 18: Lecture 30: Stellar population types, formation of Milky Way, barred galaxies, distance ladder.
  
  Problem Set #10 is due Friday, April 25 by 9:00 AM on ExpertTA.
  
  
  
• Week 12: 4/21-25                  Hubble's Law, Galaxy Types, and Galaxy Clusters [19.3-4, 26, 27]
  Monday, April 21: Lecture 31: Distance ladder, Tully-Fisher relation, Hubble's law.
  Monday, April 21: Lecture Notes: Determining distance with a Cepheid variable star.
  
  Wednesday, April 23: Lecture 32: Red shift, galaxy types.
  Wednesday, April 23: Lecture Notes: Determining distance with a type 1a supernova.
  
  Friday, April 25: Lecture 33: Galaxy types, quasars, active galactic nuclei.
  Friday, April 25: Lecture Notes: Determining the velocity of a high redshift quasar.