OUTCOME
By the end of the lesson you will be able to recognise and use the Hertzsprung Russell diagram
The Hertzsprung Russell diagram plots star luminosity vs temperature and is used to illustrate the life cycle of stars
A stars life starts in a nebula, continues through fusion and ends in one of several ways depending on its mass.
LEARNING TASKS
Explore
HR diagrams
1. Why is the HR diagram the most important diagram in Astrophysics?
2. What information can an astronomer gain from the location of a star on the diagram?
3. What is the main sequence?
4. What kind of stars are on the main sequence?
5. What is the relationship between luminosity and diameter?
Life a of a star
Explain and elaborate
Complete HR activity from CSIRO Australian National Telescope
Evaluate
Try Qs 26 - 32
1. What is the relationship between star mass and stellar lifespan?
2. Can you explain why?
3. Explain why a star expands when it runs out of hydrogen?
4. Why does the surface temperature drop?
5. Describe what ends may await a star and why one might happen rather than another.