Explorations: An Introduction to Astronomy (Arny), 7th Edition

Chapter 14: Stellar Evolution

Thought Questions

1
Stars of all colors are visible to the naked eye, from Betelgeuse's red to Sirius's white to Spica's bluewhite. If late in their lives, stars did not evolve into giants but just became dimmer and dimmer, what would you expect for the relative numbers of blue, white, yellow and red stars visible in the night sky? Would any kind of yellow stars be visible to the naked eye?
2
Inflate a balloon and carefully measure its size. Put it in the freezer for a few hours. Does it look the same when it is cold? How does this relate to how stars form in cold regions of space?
3
Describe how a protostar is believed to form.
4
Take a plastic bottle and put a little soapy water in it. Run your finger across the mouth to make a soap film. Now, without breaking the film, run hot water over the bottle. What happens to the soap film? How does this relate to what happens to a star when it is heated?
5
Suppose that stars could mix unburned fuel from their outer layers into their cores. Would that alter the way they evolve? Can you suggest some possible differences?
6
Hold a clear cylindrical water glass below a bright light so that it casts a shadow on a piece of paper. If you hold the glass at different angles, you can create different shadow patterns. Can you produce shapes similar to the planetary nebula images in figure 14.19? Is there another shape that would create patterns more similar to some images?
7
Hold a small rubber ball on top of a basketball, and drop them together toward the floor. What happens to the small ball? Does that help you understand what happens to the outer layers of a supernova as they collapse on the core?
8
Thinking about why massive stars start fusing heavy elements, and examining the periodic table in the back of the book, explain why there should be more neon, magnesium, sulfur, argon, and calcium in a supernova remnant than fluorine, sodium, phosphorus, and chlorine.
9
Explain why gold and platinum are much scarcer than iron and silicon (found in most rocks), thinking about how massive stars live and die.
10
In some very old, dense star clusters, a few blue stars, known as "blue stragglers," are seen. Why are blue stars unexpected in such clusters? If stars that stick together mix their material thoroughly when they collide, how might you explain such blue stars?
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