lect 14 part 1

lect 14 part 1 - Question61 HRdiagramfortwoopen...

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3/22/2010 1 HR diagram for two open clusters. Based on the diagram, which statement is true? Question 6 1 A. M 67 is older than NGC 188 B. M 67 is younger than NGC 188 C. Both are the exactly same age. D. There is not enough information to determine the age of the clusters. Cepheid variable stars are very luminous and can be observed over very large distances. Why are such stars important to astronomers ? A. They confirm the theory of nuclear fusion as the energy source for stars. Question 6 2 B. They can be used as distance indicators because their luminosity can be determined from their period. C. Such stars are unstable and are about to become supernovae. D. Their age can be determined directly from their period. E. They are always found in binary systems. Horizontal branch stars are stars that have left the main sequence. Inside such stars A. no fusion is occurring in the core, and hydrogen fusion is occurring in a shell around the core. Question 6 3 B. both core helium fusion and shell hydrogen fusion are taking place. C. helium fusion is occurring in the core, and there is no hydrogen fusion. D. both core hydrogen fusion and shell helium fusion are taking place.
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3/22/2010 2 A helium flash occurs A because helium is explosive and cannot be controlled when nuclear reactions occur. B because degenerate electrons in the core do not allow the core to expand as it heats up. Question 6 4 Ci n Cepheid variables. Di n stars with masses less than 0.4 Solar Mass. EN o n e of the above is true about a helium flash. What physical characteristic most determines the main sequence lifetime of a star? Ar a d i u s Question 6 5 B composition Cm a s s D luminosity class En o n e of the above When the solar core has mostly been transformed from hydrogen into helium, the Sun will move to the next phase of its life cycle, changing gradually into a Ad
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3/22/2010 3 Diagram of the evolution for a one solar mass star. Select the correct combination of answers: AT h e r e is no Hydrogen fusion during stage 2 BA t point 3, the Helium flash occurs Question 6 7 occurs. CD u r i n g stage 4, C and O fusion occurs in the core. DD u r i n g stage 5, the star becomes a red giant for a 2 nd
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lect 14 part 1 - Question61 HRdiagramfortwoopen...

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