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Conceptual Questions
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1

Why does the chemical composition of a main sequence star change most rapidly at its center?
2

Why can't hydrogen fusion and helium fusion go on at the same time at the center of a star?
3

Why do nuclei of elements other than hydrogen require higher temperatures to undergo fusion than does hydrogen?
4

What is the relationship between the opacity of the gases in a star and whether convection takes place within the star?
5

Suppose the temperature of a normal gas doubles while its density remains the same. What happens to the pressure of the gas?
6

Suppose the temperature of a degenerate gas doubles while its density remains the same. What happens to the pressure of the gas?
7

Suppose two single stars form at the same time. They have the same masses and chemical compositions. What can be said about the evolution of the two stars from that point forward?
8

What does the evolutionary track of a star tell us about its motion through space?
9

What is the relationship between isochrones and the HR diagrams of clusters of stars?
10

In cluster 1, the main sequence extends from spectral class O to spectral class K. In cluster 2, there are no main sequence stars cooler than spectral class G. Which cluster is older and how do we know?
11

What do all main sequence stars have in common?
12

How do the temperatures, masses, radii, and luminosities of the most massive main sequence stars compare with those of the least massive main sequence stars?
13

Why is it believed that there are no main sequence stars less massive than 0.08 solar mass?
14

Describe the changes in the Sun that will occur as a result of the Sun's main sequence evolution. What effect will these changes have on the Earth?
15

Why doesn't the core of a 1 solar mass star expand when helium fusion begins to raise the temperature of the core?
16

Why doesn't the energy released during a helium flash dramatically increase the brightness of the star?
17

Describe the relationship between pressure and gravity throughout a pulsation cycle of a Cepheid variable.
18

Why are AGB stars faint in the visible part of the spectrum but very luminous in the infrared?
19

What is the origin of the gas that can be seen as a planetary nebula around a hot, post-AGB star?
20

Why must there be a hot star at the center of a planetary nebula?
21

What would the chemical composition of the universe be like if the only nuclear reactions that had ever occurred in stars had been those involved in energy production?





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