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20 Cards in this Set
- Front
- Back
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On the main sequence, stars obtain their energy... |
...by converting hydrogen to helium. |
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Which of the following luminosity classes refers to stars on the main sequence? |
V |
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The faintest star visible to the naked eye has an apparent visual magnitude of about |
6 |
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Which of the following statements about an open cluster is true?
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All stars in the cluster are approximately the same age. |
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A star of spectral type O lives approximately how long on the main sequence? |
10 million years |
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A star of spectral type G lives approximately how long on the main sequence? |
10 billion years |
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On a Hertzsprung-Russell diagram, where would we find stars that are cool and luminous? |
Upper right |
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The most distant stars we can measure stellar parallax for are approximately... |
...500 parsecs away. |
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Which of the following persons used the ideas of quantum mechanics to describe why the spectral classification scheme is in order of decreasing temperature? |
Cecilia Payne-Gaposchkin |
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On a Hertzsprung-Russell diagram, where would we find white dwarfs? |
Lower left |
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Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ? |
Mass they are formed with |
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Why do astronomers often measure the visible-light apparent brightness instead of the total apparent brightness of a star? |
In order to measure the total apparent brightness of a star, you must measure its brightness in all wavelengths, and this is difficult to do. The only wavelengths you can measure from the surface of Earth are visible and radio wavelengths. |
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Which of the following persons reorganized the spectral classification scheme into the one we use today and personally classified over 400,000 stars? |
Annie Jump Cannon |
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The spectral sequence in order of decreasing temperature is... |
...OBAFGKM. |
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Suppose that you measure the parallax angle for a particular star to be 0.5 arcsecond. The distance to this star is... |
...2 parsecs. |
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In order to understand star clusters, we need to be able to estimate their ages. What technique do scientists use for this? |
Finding the main-sequence turnoff point of the stars |
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On a Hertzsprung-Russell diagram, where on the main sequence would we find stars that have the greatest mass? |
Upper left |
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Which of the following statements about apparent and absolute magnitudes is true? |
A star with apparent magnitude 1 is brighter than one with apparent magniture 2. The absolute magnitude of a star is another measure of its luminosity. A star's absolute magnitude is the apparent magnitude it would have if it were at a distance of 10 parsecs from Earth. The magnitude system that we use now is based on a system used by the ancient Greeks over 2,000 years ago that classified stars by how bright they appeared. |
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Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram? |
Surface temperature on the horizontal axis and luminosity on the vertical axis |
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A star's luminosity is the... |
...total amount of light that the star radiates each second. |
