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

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

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 

A) mass.
B) distance.
C) apparent brightness.
D) spectral type.


Answer: A

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

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

A) the star is a Cepheid variable.
B) the star is a member of an eclipsing binary star system.
C) the star is periodically ejecting gas into space, every 73 hours.
D) the star is a white dwarf.


Answer: B

To calculate the masses of stars in a binary system, we must measure their

To calculate the masses of stars in a binary system, we must measure their

A) spectral types and distance from Earth.
B) absolute magnitudes and luminosities.
C) luminosities and distance from Earth.
D) orbital period and average orbital distance.


Answer: D

Sirius is a star with spectral type A star and Rigel is a star with spectral type B star. What can we conclude?

Sirius is a star with spectral type A star and Rigel is a star with spectral type B star. What can we conclude? 

A) Rigel has a higher core temperature than Sirius.
B) Sirius has a higher core temperature than Rigel.
C) Rigel has a higher surface temperature than Sirius.
D) Sirius has a higher surface temperature than Rigel.


Answer: C

Which of the following statements about spectral types of stars is not generally true?

Which of the following statements about spectral types of stars is not generally true? 

A) The spectral type of a star can be used to determine its surface temperature.
B) The spectral type of a star can be used to determine its distance.
C) The spectral type of a star can be used to determine its color.
D) The spectral type of a star can be determined by identifying lines in its spectrum.


Answer: B

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

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) Vega is nearer than 10 parsecs from Earth.
B) Vega has a parallax angle of 1/10 arcsecond.
C) Vega's luminosity is less than that of our Sun.
D) Vega's surface temperature is cooler than the Sun.


Answer: A

A star with a parallax angle of 1/20 arcsecond is

A star with a parallax angle of 1/20 arcsecond is

A) 20 light-years away.
B) 1/20 parsec away.
C) 20 parsecs away.
D) 10 parsecs away.


Answer: C

Star A is identical to Star B, except that Star A is twice as far from us as Star B. Therefore

Star A is identical to Star B, except that Star A is twice as far from us as Star B. Therefore

A) both stars have the same luminosity, but the apparent brightness of Star B is twice that of Star A.
B) both stars have the same apparent brightness, but the luminosity of Star B is four times that of Star A.
C) both stars have the same luminosity, but the apparent brightness of Star A is four times that of Star B.
D) both stars have the same luminosity, but the apparent brightness of Star B is four times that of Star A.


Answer: D

Based on the definition of apparent brightness, which units are appropriate for its measurement?

Based on the definition of apparent brightness, which units are appropriate for its measurement? 

A) watts
B) joules
C) watts per square meter
D) Newtons


Answer: C

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?

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? 

A) its mass and its stage of life
B) its apparent brightness and its distance
C) its age and its location in the galaxy
D) its mass and its surface temperature
E) its apparent brightness and its luminosity


Answer: A

What do we mean by the main-sequence turnoff point of a star cluster, and what does it tell us?

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

Which of the following statements comparing open and globular star clusters is not true?

Which of the following statements comparing open and globular star clusters is not true? 

A) Open clusters are found only in the disk of the galaxy while globular clusters may be found both in the disk and the halo of the galaxy.
B) Stars in open clusters are relatively young while stars in globular clusters are very old.
C) Open and globular clusters each typically contain a few hundred stars.
D) For both open and globular clusters, we can assume that all the stars in a particular cluster are about the same age.


Answer: C

What is a white dwarf?

What is a white dwarf? 

A) It is a main-sequence star of spectral type F, which tends to look white in colour.
B) It is the remains of a star that ran out of fuel for nuclear fusion.
C) It is a type of star that produces energy by gravitational contraction.
D) It is a star that follows a period-luminosity relation.


Answer: B

Suppose our Sun were suddenly replaced by a supergiant star. Which of the following would be true?

Suppose our Sun were suddenly replaced by a supergiant star. Which of the following would be true? 

A) Earth would be inside the supergiant.
B) The supergiant's surface temperature would be much hotter than the surface temperature of our Sun.
C) Earth would fly off into interstellar space.
D) The supergiant would appear as large as the full Moon in our sky.


Answer: A

What is the common trait of all main-sequence stars?

What is the common trait of all main-sequence stars? 

A) They are in the final stage of their lives.
B) They generate energy through hydrogen fusion in their core.
C) They are all spectral type G.
D) They all have approximately the same mass.


Answer: B

Each choice below lists a spectral type and luminosity class for a star. Which one is a red supergiant?

Each choice below lists a spectral type and luminosity class for a star. Which one is a red supergiant? 

A) spectral type M1, luminosity class V
B) spectral type O9, luminosity class I
C) spectral type G2, luminosity class V
D) spectral type M2, luminosity class I


Answer: D