1. Describe the stars in this picture.
2. Briefly explain how we can learn about the lives of stars, even though their lives are far longer than human lives.
3. In what ways are all stars similar? In what ways do they differ?
4. How is a star's apparent brightness related to its luminosity? Explain by describing the inverse square law for light.
5. Briefly explain how we use stellar parallax to determine a star's distance. Once we know a star's distance, how can we determine its luminosity?
6. Other than parallax, is there a way to measure the distance to stars? Explain carefully
7. What does this illustrate?
8. What do we mean by a star's spectral type? How is a star's spectral type related to its surface temperature and color? Which stars are hottest and coolest in the spectral sequence OBAFGKM?
9. If stars are mostly hydrogen and helium why don't we see hydrogen and helium spectral lines in all stars?
10. I saw a star with a temperature of 10,000K with no hydrogen lines. What is happening? [Remember the spectrum for an A star.]
11. What are the three basic types of binary star systems? Why are binaries so important to measuring masses of stars?
12. Draw a sketch of a basic Hertzsprung-Russell (H-R) diagram. Label the main sequence, giants, supergiants, and white dwarfs. Where on this diagram do we find stars that are cool and dim? Cool and luminous? Hot and dim? Hot and luminous?
13. What do we mean by a star's luminosity class? What does the luminosity class tell us about the star? Briefly explain how we classify stars by spectral type and luminosity class.
What is the defining characteristic of a
main-sequence star? Briefly explain why massive main-sequence stars are
more luminous and have hotter surfaces than less massive main-sequence
14B. Why does the Mass-Luminosity relationship apply to only Main Sequence stars?
15. Which stars have longer lifetimes: massive stars or less massive stars? Explain why.
16. Why is a star's birth mass its most fundamental property?
17. How do giants and supergiants differ from main-sequence stars? What are white dwarfs?
18. How does the luminosity of a pulsating variable star change with time?
19. What is this? About how old is it?
20. Describe in general terms how open clusters and globular clusters differ in their numbers of stars, ages, and locations in the galaxy.
21. Explain why H-R diagrams look different for star clusters of different ages. How does the location of the main-sequence turnoff point tell us the age of the star cluster?
22. Using the information in this H-R diagram, describe how Proxima Centauri differs from Sirius. Do the same for Sirius B and the Sun.
Decide whether the statement makes sense (or is clearly true) or does not make sense (or is clearly false). Explain clearly; not all these have definitive answers, so your explanation is more important than your chosen answer.
23. Two stars that look very different must be made of different kinds of elements.
24. Two stars that have the same apparent brightness in the sky must also have the same luminosity.
25. Sirius looks brighter than Alpha Centauri, but we know that Alpha Centauri is closet because its apparent position in the sky shifts by a larger amount as Earth orbits the Sun.
26. Stars that look red have hotter surfaces than stars that look blue.
27. Some of the stars on the main sequence of the H-R diagram are not converting hydrogen into helium.
28. The smallest, hottest stars are plotted in the lower left-hand portion of the H-R diagram.
29. Stars that begin their lives with the most mass live longer than less massive stars because they have so much more hydrogen fuel.
30. Star clusters with lots of bright, blue stars of spectral type O and B are generally younger than clusters that don't have any such stars.
31. All giants, supergiants, and white dwarfs were once main-sequence stars.
32. Most of the stars in the sky are more massive than the Sun.