What do we mean by the main-sequence turnoff point of a star cluster, and what does it tell us?
A) It is the point in a star cluster beyond which main-sequence stars are not found, and it tells us the cluster's distance.
B) It is the spectral type of the hottest main-sequence star in a star cluster, and it tells us the cluster's age.
C) It is the luminosity class of the largest star in a star cluster, and it tells us the cluster's age.
D) It is the mass of the most massive star in the star cluster, and it tells us the cluster's size.
Answer: B
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Astronomy Chapter 15
- The choices below each describe the appearance of an H-R diagram for a different star cluster. Which cluster is most likely to be located in the halo of our galaxy?
- The choices below each describe the appearance of an H-R diagram for a different star cluster. Which cluster is the youngest?
- How did astronomers discover the relationship between spectral type and mass for main-sequence stars?
- The approximate main-sequence lifetime of a star of spectral type O is
- You observe a star and you want to plot it on an H-R diagram. You will need to measure all of the following, except the star's
- Careful measurements reveal that a star maintains a steady apparent brightness at most times, except that at precise intervals of 73 hours the star becomes dimmer for about 2 hours. The most likely explanation is that
- To calculate the masses of stars in a binary system, we must measure their
- Sirius is a star with spectral type A star and Rigel is a star with spectral type B star. What can we conclude?
- Which of the following statements about spectral types of stars is not generally true?
- The star Vega has an absolute magnitude of about 4 and an apparent magnitude of about 0. Based on the definitions of absolute and apparent magnitude, we can conclude that
- A star with a parallax angle of 1/20 arcsecond is
- Star A is identical to Star B, except that Star A is twice as far from us as Star B. Therefore
- Based on the definition of apparent brightness, which units are appropriate for its measurement?
- All stars are born with the same basic composition, yet stars can look quite different from one another. Which two factors primarily determine the characteristics of a star?
- Which of the following statements comparing open and globular star clusters is not true?
- What is a white dwarf?
- Suppose our Sun were suddenly replaced by a supergiant star. Which of the following would be true?
- What is the common trait of all main-sequence stars?
- Each choice below lists a spectral type and luminosity class for a star. Which one is a red supergiant?
- How is the lifetime of a star related to its mass?
- On an H-R diagram, stellar masses
- On an H-R diagram, stellar masses
- On an H-R diagram, stellar radii
- The axes on a Hertzsprung-Russell (H-R) diagram represent