Question 1

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

Accepted Answer

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. 
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.

Question 2

Approximately,what basic composition are all stars born with?

Accepted Answer

A) half hydrogen,half helium,no more than 2 percent heavier elements 
B) three-quarters hydrogen,one-quarter helium,no more than 2 percent heavier elements 
C) 90 percent hydrogen,10 percent helium,no more than 1 percent heavier elements 
D) one-quarter hydrogen,three-quarters helium,no more than 2 percent heavier elements 
E) 98 percent hydrogen,2 percent helium 
A) half hydrogen,half helium,no more than 2 percent heavier elements 
B) three-quarters hydrogen,one-quarter helium,no more than 2 percent heavier elements 
C) 90 percent hydrogen,10 percent helium,no more than 1 percent heavier elements 
D) one-quarter hydrogen,three-quarters helium,no more than 2 percent heavier elements 
E) 98 percent hydrogen,2 percent helium

Question 3

Which of the following characteristics of stars has the greatest range in values?

Accepted Answer

A) mass 
B) radius 
C) core temperature 
D) surface temperature 
E) luminosity 
A) mass 
B) radius 
C) core temperature 
D) surface temperature 
E) luminosity

Question 4

Ten parsecs is about

Accepted Answer

A) 150 million kilometers. 
B) 10,000 seconds. 
C) 10 parallax seconds of angle. 
D) 32.6 light-years. 
A) 150 million kilometers. 
B) 10,000 seconds. 
C) 10 parallax seconds of angle. 
D) 32.6 light-years.

Question 5

Refer to the choices in the table for the following questions.
  
-Which star has the highest surface temperature?

Accepted Answer

The answer of Refer to the choices in the table...

Question 6

Earth is about 150 million km from the Sun,and the apparent brightness of the Sun in our sky is about 1,300 watts per square meter.Determine the apparent brightness we would measure for the Sun if we were located one-third of Earth's distance from the Sun.

Accepted Answer

The Sun would appear nine time

Question 7

Which of the following terms is given to a pair of stars that we can determine are orbiting each other only by measuring their periodic Doppler shifts?

Accepted Answer

A) eclipsing binary 
B) spectroscopic binary 
C) visual binary 
D) double star 
A) eclipsing binary 
B) spectroscopic binary 
C) visual binary 
D) double star

Question 8

On an H-R diagram,stellar masses

Accepted Answer

A) can be determined for main-sequence stars but not for other types of stars. 
B) are greatest in the lower left and least in the upper right. 
C) decrease from upper left to lower right. 
D) are impossible to determine. 
A) can be determined for main-sequence stars but not for other types of stars. 
B) are greatest in the lower left and least in the upper right. 
C) decrease from upper left to lower right. 
D) are impossible to determine.

Question 9

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

Accepted Answer

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

Question 10

From hottest to coolest,the order of the spectral types of stars is

Accepted Answer

A) OBAFGKM. 
B) OBAGFKM. 
C) ABFGKMO. 
D) OMKGFBA. 
E) ABCDEFG. 
A) OBAFGKM. 
B) OBAGFKM. 
C) ABFGKMO. 
D) OMKGFBA. 
E) ABCDEFG.

Question 11

Why is the spectral sequence of stars not alphabetical?

Accepted Answer

A) The letters refer to the initials of the original discovers. 
B) The original alphabetical labeling did not correspond to surface temperature and thus had to be reordered. 
C) They were chosen to fit a mnemonic. 
D) Because there is still uncertainty over what generates the energy in stellar cores. 
E) Because it refers to stellar masses and these were difficult to measure accurately. 
A) The letters refer to the initials of the original discovers. 
B) The original alphabetical labeling did not correspond to surface temperature and thus had to be reordered. 
C) They were chosen to fit a mnemonic. 
D) Because there is still uncertainty over what generates the energy in stellar cores. 
E) Because it refers to stellar masses and these were difficult to measure accurately.

Question 12

The following questions refer to the sketch of the H-R diagram below.Please choose the best answer in each case,i.e. ,choice (a)refers to the entire main sequence,while (c)and (d)refer to only small parts of the main sequence.If choice (c)or (d)offers a better answer to a particular question than (a),use the best choice.You may use the same choice more than once.
  
-Which group represents stars that are hot but dim?

Accepted Answer

The answer of The following questions refer to the sketch...

Question 13

On a Hertzsprung-Russell diagram,where would we find stars that are cool and luminous?

Accepted Answer

A) upper right 
B) lower right 
C) upper left 
D) lower left 
A) upper right 
B) lower right 
C) upper left 
D) lower left

Question 14

All stars spend approximately the same amount of time on the main sequence.

Accepted Answer

A) True 
 B)False

Question 15

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

Accepted Answer

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. 
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.

Question 16

Which of the following is the most common type of main-sequence star?

Accepted Answer

A) an O star 
B) an A star 
C) an F star 
D) an M star 
E) a G star 
A) an O star 
B) an A star 
C) an F star 
D) an M star 
E) a G star

Question 17

The axes on a Hertzsprung-Russell (H-R)diagram represent

Accepted Answer

A) mass and luminosity. 
B) luminosity and surface temperature. 
C) luminosity and apparent brightness. 
D) mass and radius. 
A) mass and luminosity. 
B) luminosity and surface temperature. 
C) luminosity and apparent brightness. 
D) mass and radius.

Question 18

Process of Science: What is a basic assumption that is made when we measure stellar masses by observing their orbits?

Accepted Answer

We assume that the stars move around eac

Question 19

Why are Cepheid variables so important for measuring distances in astronomy?

Accepted Answer

A) They all have the same luminosity. 
B) They all have the same period. 
C) Their luminosity can be inferred from their period. 
D) They are close enough to have a detectable parallax. 
E) They are circumpolar like Polaris,the North Star. 
A) They all have the same luminosity. 
B) They all have the same period. 
C) Their luminosity can be inferred from their period. 
D) They are close enough to have a detectable parallax. 
E) They are circumpolar like Polaris,the North Star.

Question 20

Assuming that we can measure the apparent brightness of a star,what does the inverse square law for light allow us to do?

Accepted Answer

A) Determine both the star's distance and luminosity from its apparent brightness. 
B) Determine the distance to the star from its apparent brightness. 
C) Calculate the star's luminosity if we know its distance,or calculate its distance if we know its luminosity. 
D) Calculate the star's surface temperature if we know either its luminosity or its distance. 
A) Determine both the star's distance and luminosity from its apparent brightness. 
B) Determine the distance to the star from its apparent brightness. 
C) Calculate the star's luminosity if we know its distance,or calculate its distance if we know its luminosity. 
D) Calculate the star's surface temperature if we know either its luminosity or its distance.

Exam 15: Surveying the Stars

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

Approximately,what basic composition are all stars born with?

Which of the following characteristics of stars has the greatest range in values?

Ten parsecs is about

Refer to the choices in the table for the following questions. -Which star has the highest surface temperature?

Earth is about 150 million km from the Sun,and the apparent brightness of the Sun in our sky is about 1,300 watts per square meter.Determine the apparent brightness we would measure for the Sun if we were located one-third of Earth's distance from the Sun.

Which of the following terms is given to a pair of stars that we can determine are orbiting each other only by measuring their periodic Doppler shifts?

On an H-R diagram,stellar masses

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

From hottest to coolest,the order of the spectral types of stars is

Why is the spectral sequence of stars not alphabetical?

On a Hertzsprung-Russell diagram,where would we find stars that are cool and luminous?

All stars spend approximately the same amount of time on the main sequence.

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

Which of the following is the most common type of main-sequence star?

The axes on a Hertzsprung-Russell (H-R)diagram represent

Process of Science: What is a basic assumption that is made when we measure stellar masses by observing their orbits?

Why are Cepheid variables so important for measuring distances in astronomy?

Assuming that we can measure the apparent brightness of a star,what does the inverse square law for light allow us to do?

A Modern View of the Universe

Discovering the Universe for Yourself

The Science of Astronomy

Making Sense of the Universe: Understanding Motion, Energy, and Gravity

Light and Matter: Reading Messages from the Cosmos

Telescopes: Portals of Discovery

Our Planetary System

Formation of the Solar System

Planetary Geology: Earth and the Other Terrestrial Worlds

Planetary Atmospheres: Earth and the Other Terrestrial Worlds

Jovian Planet Systems

Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

Other Planetary Systems: The New Science of Distant Worlds

Our Star

Star Birth

Star Stuff

The Bizarre Stellar Graveyard

Our Galaxy

Galaxies and the Foundations of Modern Cosmology

Galaxy Evolution

The Birth of the Universe

Dark Matter, Dark Energy, and the Fate of the Universe

Life in the Universe

Celestial Timekeeping and Navigation

Space and Time

Spacetime and Gravity

Building Blocks of the Universe

Filters