1. Stellar evolution describes how stars change over their lifetime. Stars are born from clouds of gas and dust in space, like the Orion Nebula. 2. Young stars called protostars form at the centers of gas clouds through gravitational collapse. Stars spend most of their lives fusing hydrogen into helium in their cores through nuclear fusion, staying in hydrostatic equilibrium. 3. Massive stars over 8 solar masses die dramatically in supernova explosions, forging heavy elements. Less massive stars end as white dwarfs or neutron stars.

1. Astronomy: A Self-Teaching Guide
Ch. 05: Stellar Evolution
1. Define: Stellar Evolution
2. Where do stars form? Where is a famous example?
3. What is a protostar?
4. Define: Hydrostatic Equilibrium
5. Describe the sun’s evolutionary track on the H-R Diagram. Where do stars spend most of their
time on the H-R Diagram?
6. Describe nuclear fusion.
7. Which stars live shortest? Longest? What dictates a star’s life span?
8. Describe the changes in a star when it becomes a red giant. What are some “good examples” of
red giant stars visible in the night sky?

2. 9. Astronomers believe that elements like carbon and oxygen, which we need for life, are made
where?
10. What are variable stars? What are Cepheid variable stars useful for?
11. Describe the following types of stars:
RR Lyrae variables
Mira variables
12. What characteristic of a star determines the way that it dies?
13. Describe the death of the following stars:
Small stars (≤ 8 solar masses) Large stars (> 8 solar masses)
14. What is a famous planetary nebula?
15. What is a white dwarf? A nova?

3. 16. Place the following stages in the life of the sun in order of occurrence:
_____ Dead, black dwarf in space
_____ Evolution to red giant when helium core forms
_____ Planetary nebula, enriched hydrogen envelope ejected into space
_____ Protostar, gravitational contraction of gas and dust
_____ Red giant, shining by helium fusion
_____ Stable, main sequence star, shining by hydrogen fusion
_____ Variable star, formation of carbon core
_____ White dwarf, mass packed into sphere the size of the earth
17. What kind of stars die as supernovas?
18. What types of elements are produced in supernova explosions?
19. What is a famous supernova remnant?
20. What are neutron stars? How are neutron stars related to pulsars?
21. Describe a black hole.