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Why are large telescopes valuable in astronomy? |
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2 | |
A photograph of a star cluster shows many more stars than can be seen by looking by eye at the cluster through the same telescope. Why is there a difference? |
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3 | |
Why do you think it is useful to put an astronomical telescope in a satellite? |
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4 | |
What part of a star is responsible for the continuous bright background of its spectrum? What happens to the radiation produced underneath this part of the star? What part of the star is responsible for the dark absorption lines? |
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5 | |
Arrange the following types of stars in order of decreasing surface temperature: yellow stars, blue stars, white stars, red stars. |
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6 | |
Suppose a star had a cool interior surrounded by a hot atmosphere. What kind of spectrum would it have? |
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7 | |
Suppose you examine the spectra of two stars receding from the earth and find that the lines in one are displaced farther toward the red end than those in the other. What conclusion can you draw? |
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8 | |
Suppose the earth's magnetic field were to disappear. What effect would this have on the aurora? |
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9 | |
Why do sunspots appear dark if their temperatures are over 4500 K? |
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10 | |
Give two methods for determining how fast the sun rotates on its axis. Is the rotation speed the same for the entire sun? |
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11 | |
What aspect of sunspots changes during a sunspot cycle? |
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12 | |
Why is the sun's corona ordinarily not visible? How do we know it exists? |
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13 | |
What evidence suggests that the sun is almost wholly gaseous? |
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14 | |
What evidence can you suggest to support the hypothesis that the sun's radiation rate has not changed appreciably in the past 2 billion years or so? |
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15 | |
Why do you think astronomers believe that the sun's energy originates in its interior rather than in its surface layers? |
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16 | |
What element is most abundant on the sun? Next most abundant? |
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17 | |
How can the composition of the sun be determined? |
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18 | |
Helium was discovered in the sun before it was found on the earth (hence its name, which comes from helios, the Greek word for "sun"). How can this sequence have come about? |
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19 | |
What aspect of the formation of helium from hydrogen results in the evolution of energy? |
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20 | |
How are stellar masses determined? |
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21 | |
Which varies more, the masses of the stars or their sizes? |
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22 | |
What data are needed to determine a star's average density? How would you expect the density to change from the surface layers to the interior? |
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23 | |
Which stars do you think have the highest densities? The lowest? |
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24 | |
A red star and a white star of the same apparent brightness are the same distance from the earth. Which is larger? Why? |
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25 | |
Explain how the distance to a star cluster that contains Cepheid variables is determined. |
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26 | |
Where are the lighter elements created? The heavier ones? |
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27 | |
How is a star's diameter estimated from measurements of temperature and intrinsic brightness? |
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28 | |
Why are relatively few stars very hot? |
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29 | |
What information can be gained by comparing the intrinsic and apparent brightnesses of a star? |
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30 | |
What information can be gained from a knowledge of the surface temperature and intrinsic brightness of a star? |
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31 | |
The spectrum of a certain star shows a doppler shift that varies periodically from the red to the blue end of the spectrum. What kind of star is this? |
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32 | |
Must a star be spherical? |
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33 | |
Is it possible for an object with the mass and composition of the sun to exist without radiating energy? |
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34 | |
Why is the sun considered to be a star? |
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35 | |
Why are most stars part of the main sequence on the H-R diagram? |
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36 | |
Main-sequence stars are supposed to evolve into red giants, but relatively few stars lie between the main sequence and the group of red giants on the H-R diagram. Why? |
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37 | |
Why do main-sequence stars have masses that lie between about 1\40 and 100 times the mass of the sun? |
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38 | |
A giant star is much redder than a main-sequence star of the same intrinsic brightness. How does this observation indicate that the giant star is larger than the main-sequence star? |
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39 | |
What are the chief characteristics of an average star in the upper left of the H-R diagram? In the lower left? In the upper right? In the middle of the main sequence? |
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40 | |
Where would a star be located in the main sequence relative to the sun if its mass is less than half that of the sun? Would it remain in the main sequence for a shorter or longer time than the sun? Would it be cooler or hotter than the sun? |
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41 | |
Sirius, the brightest star in the sky apart from the sun, is a blue-white star of great intrinsic brightness. (a) What does this suggest about its temperature? (b) About its average density? (c) About its position in the H-R diagram? |
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42 | |
As a main-sequence star evolves, what happens to its position on the main sequence? |
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43 | |
Why are there relatively few giant stars in the main sequence? |
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44 | |
Which of the following types of star is the smallest? The largest? The most common? Neutron stars, white dwarfs, red dwarfs, black dwarfs. |
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45 | |
Which of the following types of star is the most common in the sky? Least common? Main-sequence stars, white dwarfs, red giants, supernovas, double stars, Cepheid variables. |
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46 | |
Into what kind of star will the sun eventually evolve? |
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47 | |
In what part of its life cycle is a white dwarf star? |
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48 | |
What happens to a very heavy star at the end of its period in the main sequence? |
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49 | |
After a very long time, a white dwarf will cool down and become a black dwarf. What will the corresponding evolutionary path of the star be on the H-R diagram? |
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50 | |
What is left behind after a supernova explosion? |
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51 | |
(a) What is the characteristic behavior of a pulsar? (b) What is believed to be its nature? (c) From what does a pulsar originate? |
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52 | |
What prevents light from escaping from a black hole? |
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53 | |
How large are black holes? Can any star evolve into a black hole? |
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