Module 2: Stars & Stellar Evolution
Weeks 7–13 | How stars work and how they die
Why this module matters
Stars are not static points of light — they are dynamic nuclear furnaces held in delicate balance by gravity and pressure. This module takes you inside stars to understand how they generate energy, how we measure their properties, and how they evolve over billions of years.
Module 2 is where many of astronomy’s most important hidden quantities finally come into focus. We use the Sun as a nearby physics lab, learn how distance and luminosity can be inferred from light, organize stars on the H-R diagram, and then follow stellar lives from birth to death. By the end of the module, the night sky should feel less like a collection of points and more like a population with structure, history, and fate.
Learning objectives
By the end of this module, you will be able to:
- Explain how the Sun generates energy through nuclear fusion
- Distinguish apparent brightness, luminosity, and distance, and use parallax as the first rung of the distance ladder
- Interpret the H-R diagram as an organizing map of stellar properties and evolutionary state
- Describe how binary stars reveal stellar masses
- Explain how stars form from interstellar clouds and why stellar mass determines lifetime and fate
- Trace stellar evolution from birth to death for different mass stars
Lecture Readings
These 8 lecture readings are the primary required materials for Module 2.
Lecture 14: Our Star: The Sun
March 9, 2026The Sun is our nearest star and the Rosetta Stone for understanding all stars. We decode its structure, energy generation, and activity.
Lecture 15: Measuring the Stars
March 11, 2026How we infer stellar distances and intrinsic brightness from parallax angles and flux measurements.
Lecture 16: The H-R Diagram
March 16, 2026When temperature and luminosity are plotted against each other, thousands of stars reveal hidden patterns that unlock the physics of stellar structure and evolution.
Lecture 17: Binary Stars & Stellar Masses
March 18, 2026How we measure stellar masses using binary systems and gravity.
Lecture 18: From Gas to Stars
March 23, 2026How gas and dust clouds collapse to form protostars, disks, and the next generation of stars.
Lecture 19: Stellar Evolution
March 25, 2026A star’s life is a battle between gravity pulling in and pressure pushing out. When the fuel runs out, the balance changes, and what happens next depends primarily on mass.
Lecture 20: How Stars Die
April 6, 2026How stellar mass determines whether a star ends as a white dwarf, a neutron star, or a black hole.
Lecture 21: Neutron Stars and Black Holes
April 8, 2026How compact stellar remnants reveal extreme gravity, dense matter, and gravitational waves.
Solutions
Lecture 14-21 solutions are now posted on the student site:
Lecture Slides (Optional Archive / In Progress)
Slide decks for Module 2 are optional archive materials and may be posted as they are finalized.
Optional Reference (OpenStax Astronomy 2e)
Lecture readings are provided on this website. For additional depth, see the free OpenStax Astronomy 2e:
- Chapter 15: The Sun
- Chapters 17–18: Analyzing Starlight; The Stars
- Chapters 20–23: Star Formation through Black Holes
- What triggers core-collapse supernovae? We know massive stars explode, but the exact mechanism is still debated.
- What is the maximum neutron star mass? Above ~2-3 M☉ they collapse to black holes, but the exact limit depends on unknown nuclear physics.
- Why do some massive stars collapse directly to black holes? The “island of explodability” is not fully understood.