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21 Cards in this Set
- Front
- Back
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What is the Hertzsprung-Russell diagram, or H-R diagram?
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A plot of the luminosity of stars against their spectral class or effective disk temperatures. |
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What does the H-R diagram include? |
The main sequence of the H-R diagram extends diagonally from hot, luminous stars on the upper left to cool ones of low luminosity in the lower right. |
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What are the red giant stars? |
Luminous stars with cool disk temperatures found in the upper right side of the H-R diagram |
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What are supergiant stars? |
Supergiant stars are very rare, extremely luminous, and very massive. They are located along the top of the H-R diagram. |
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What are the white dwarf stars? |
The white dwarf stars are hot stars of low luminosity, found in the bottom left side of the H-R diagram. |
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How to determine the star's luminosity and effective disk temperature? |
The luminosity class and spectral class of a star can be combined to determine the star’s luminosity and effective disk temperature. |
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When does a star begin to shine? When are massive stars and low mass stars on the main sequence? |
A star begins to shine when it arrives on the main sequence of the H-R diagram. Very massive stars are found on the upper left side of the main sequence, and they have short lifetimes of about 10 million years. Low mass stars are found in the bottom right side of the main sequence, and they can have lifetimes as long as 10 billion to 100 billion years. |
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How do main-sequence stars shine? |
Main-sequence stars shine by hydrogen burning, or the nuclear fusion of protons into helium nuclei, in their hot centers. |
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How do the Sun and all other main-sequence stars with a mass less than about 1.5 times the mass of the Sun shine? |
The Sun and all other main-sequence stars with a mass less than about 1.5 times the mass of the Sun shine by the proton-proton chain of hydrogen-burning nuclear reactions. |
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How do main-sequence stars of more than 1.5 times the Sun’s mass shine? |
Main-sequence stars of more than 1.5 times the Sun’s mass shine by the CNO cycle of hydrogen-burning nuclear reactions in which carbon acts as a catalyst in the conversion of protons into helium nuclei. |
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What happens when a main-sequence star has exhausted its supply of hydrogen fuel? |
The star’s core collapses and heats up to a temperature that is high enough to burn helium nuclei into carbon nuclei. At the same time, the outer atmosphere of the star expands and cools to form a red giant star. |
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What are the characteristics of stars within star clusters? |
Stars within star clusters are all of about the same age and initial chemical composition. |
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What can the H-R diagram of globular star clusters be used for? |
The H-R diagram of globular star clusters can be used to delineate the course of stellar evolution. The most luminous and massive stars, found in the upper left part of the main sequence, are the first to leave the main sequence; their turnoff point in the H-R diagram can be used to clock the age of the star cluster. |
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What is happening to the observed abundance of the elements in the Sun with increasing atomic weight? |
There is an exponential decline in the observed abundance of the elements in the Sun with increasing atomic weight. The most abundant element is hydrogen, the lightest element. |
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How were hydrogen and helium formed? |
The hydrogen and most of the helium in the Sun and other stars was formed in the first moments of the big bang that gave rise to the expanding universe. |
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What are the eliminated synthesized inside giant or supergiant stars? |
Carbon, oxygen, and nitrogen. |
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When do heavier elements originate? |
Heavier elements originate during the explosive death of very massive stars. |
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What did the first stars contain? |
The first stars could only contain hydrogen and helium, for no heavier elements had yet been formed. |
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What did the second generation of stars contain? |
The second generation of stars, including the Sun, originated from interstellar material that had been seeded with heavier elements synthesized within massive, first-generation stars. |
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How old are the oldest first generation stars? |
The oldest first generation stars can be nearly 14 billion years old, the approximate age of the expanding universe. |
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How old is the Sun? |
The Sun is 4.6 billion years old and a second generation star. |
