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 most likely to be located in the halo of our galaxy? 

A) The diagram shows main-sequence stars of every spectral type except O, along with a few giants and supergiants.
B) The diagram shows main-sequence stars of spectral types G, K, and M, along with numerous giants and white dwarfs.
C) The diagram shows main-sequence stars of all the spectral types except O and B, along with a few giants and supergiants.
D) The diagram shows no main-sequence stars at all, but it has numerous supergiants and white dwarfs.


Answer: B

The choices below each describe the appearance of an H-R diagram for a different star cluster. Which cluster is the youngest?

The choices below each describe the appearance of an H-R diagram for a different star cluster. Which cluster is the youngest? 

A) The diagram shows main-sequence stars of spectral types G, K, and M, along with numerous giants and white dwarfs.
B) The diagram shows main-sequence stars of all the spectral types except O and B, along with a few giants and supergiants.
C) The diagram shows main-sequence stars of every spectral type except O, along with a few giants and supergiants.
D) The diagram shows no main-sequence stars at all, but it has numerous supergiants and white dwarfs.


Answer: C

How did astronomers discover the relationship between spectral type and mass for main-sequence stars?

How did astronomers discover the relationship between spectral type and mass for main-sequence stars? 

A) by using computer models of hydrogen fusion and stellar structure
B) by measuring stellar radii with very powerful telescopes
C) by comparing stars with the same spectral type but different luminosities
D) by measuring the masses and spectral types of main-sequence stars in binary systems


Answer: D

The approximate main-sequence lifetime of a star of spectral type O is

The approximate main-sequence lifetime of a star of spectral type O is

A) 10,000 years.
B) 3 million years.
C) 300 million years.
D) 10 billion years.


Answer: B