SELF-TEST: FILL IN THE BLANK
1. In stage 1 of prestellar evolution, a typical interstellar cloud has the following properties: temperature _____ K, size _____ pc, mass _____ solar masses.
2. In stage 2 of prestellar evolution, a contracting interstellar cloud _____ into smaller pieces.
3. During stage 3 of prestellar evolution, as each piece of the original interstellar cloud continues to contract, its central density and temperature _____.
4. At stage 4 of prestellar evolution, a piece of the interstellar cloud becomes a _____.
5. A stage 4 object is plotted in the _____ (upper/lower) _____ (right/left) part of the H–R diagram.
6. At stage 6 the central temperature of the object reaches _____ K.
7. At this temperature, a stage 6 object begins to _____.
8. When hydrogen is fusing stably in the core, the star has reached the _____.
9. It takes a star like the Sun a total of about _____ million years to form.
10. More massive stars evolve more _____.
REVIEW AND DISCUSSION
11. What is a shock wave? Of what significance are shock waves in star formation?
12. Briefly describe the basic chain of events leading to the formation of a star like the Sun?
13. Why do stars tend to form in groups?
14. Why does the evolution of a protostar slow down as it approaches the main sequence?
15. In what ways do the formative stages of high-mass stars differ from those of stars like the Sun?
16. What are brown dwarfs?
17. At what evolutionary stages must astronomers use radio and infrared radiation to study prestellar objects? Why can’t they use visible light?
18. Compare and contrast the observed properties of open star clusters and globular star clusters.
19. In the formation of a star cluster with a wide range of stellar masses, is it possible for some stars to die out before others have finished forming? Do you think this will have any effect on the cluster’s formation?
20. What do star clusters and associations have to do with star formation?
Learning Goals
Discuss the factors that compete against gravity in the process of star formation.Summarize the sequence of events leading to the formation of a star like our Sun.
Explain how the process of star formation depends on stellar mass.
Describe some of the observational evidence supporting the modern theory of star formation.
Explain the nature of interstellar shock waves, and discuss their possible role in the formation of stars.
Distinguish between open and globular star clusters, and explain why the study of clusters is important to astronomers.