Question 1

The age of a cluster can be estimated by

Accepted Answer

A) Observing the number of stars-larger numbers imply older cluster 
B) Observing the number of stars-larger numbers imply younger cluster 
C) Plotting the stars on an HR diagram-lower turnoff implies younger 
D) Plotting the stars on an HR diagram-lower turnoff implies older 
E) Plotting the stars on a color-color diagram-lower values imply older 
A) Observing the number of stars-larger numbers imply older cluster 
B) Observing the number of stars-larger numbers imply younger cluster 
C) Plotting the stars on an HR diagram-lower turnoff implies younger 
D) Plotting the stars on an HR diagram-lower turnoff implies older 
E) Plotting the stars on a color-color diagram-lower values imply older

Question 2

Cluster A has no stars of spectral type O,B,and A on its main sequence,whereas cluster B has stars of all types but O on its main sequence.Which of the following correctly describes the relative ages of clusters A and B?

Accepted Answer

A) The above information is insufficient to determine the relative ages 
B) Both clusters are older than the Sun 
C) Cluster A is older than B 
D) Cluster B is older than A 
A) The above information is insufficient to determine the relative ages 
B) Both clusters are older than the Sun 
C) Cluster A is older than B 
D) Cluster B is older than A

Question 3

One reason that Cepheid stars are important to astronomers is that

Accepted Answer

A) They are especially rich in metal content 
B) There is a definite relationship between variability period and luminosity 
C) They are all in the plane of the galaxy-so center can be measured 
D) They can be seen even in distant clusters of galaxies 
E) They are very young,so stellar evolution can be studied in detail 
A) They are especially rich in metal content 
B) There is a definite relationship between variability period and luminosity 
C) They are all in the plane of the galaxy-so center can be measured 
D) They can be seen even in distant clusters of galaxies 
E) They are very young,so stellar evolution can be studied in detail

Question 4

Estimate the main sequence lifetime for a star that is twice as massive as the Sun and 8 times as luminous.

Accepted Answer

A) 16 times the Sun's main sequence lifetime 
B) One-quarter the Sun's main sequence lifetime 
C) One-eighth the Sun's main sequence lifetime 
D) Twice the Sun's main sequence lifetime 
A) 16 times the Sun's main sequence lifetime 
B) One-quarter the Sun's main sequence lifetime 
C) One-eighth the Sun's main sequence lifetime 
D) Twice the Sun's main sequence lifetime

Question 5

What limits the formation of giant stars of extremely large sizes?

Accepted Answer

A) Fusion pressures get larger as the size of the star grows,eventually blowing the star into smaller pieces. 
B) Heavy elements in the core exert an outward pressure,preventing the formation of a large core. 
C) Gas pressure from the outer layers of the star blow the star apart. 
D) The core collapses suddenly,causing an explosion before the core can form. 
A) Fusion pressures get larger as the size of the star grows,eventually blowing the star into smaller pieces. 
B) Heavy elements in the core exert an outward pressure,preventing the formation of a large core. 
C) Gas pressure from the outer layers of the star blow the star apart. 
D) The core collapses suddenly,causing an explosion before the core can form.

Question 6

What causes Cepheid variables to vary in brightness?

Accepted Answer

A) They pulsate 
B) Eclipses 
C) Changes in nuclear energy generation rate 
D) Obscuration by clouds of dust 
A) They pulsate 
B) Eclipses 
C) Changes in nuclear energy generation rate 
D) Obscuration by clouds of dust

Question 7

As soon as its core hydrogen is exhausted,a star like the Sun begins to evolve

Accepted Answer

A) Toward the upper right in the H-R diagram 
B) Toward the zero age main sequence stage 
C) Up the main sequence to become an O star 
D) Toward the lower left in the H-R diagram 
A) Toward the upper right in the H-R diagram 
B) Toward the zero age main sequence stage 
C) Up the main sequence to become an O star 
D) Toward the lower left in the H-R diagram

Question 8

Based on your knowledge of the H-R diagram,which of the descriptions of a star cluster is astrophysical nonsense?

Accepted Answer

A) A complete main sequence with no red giants and no white dwarfs 
B) A complete main sequence except no O stars,there are some red giants 
C) A complete main sequence,no red giants but a large number of white dwarfs 
D) No stars of spectral classes O,B,or A,but red giants and white dwarfs 
A) A complete main sequence with no red giants and no white dwarfs 
B) A complete main sequence except no O stars,there are some red giants 
C) A complete main sequence,no red giants but a large number of white dwarfs 
D) No stars of spectral classes O,B,or A,but red giants and white dwarfs

Question 9

The lifetime of a star half the mass of the Sun has what relationship to our Sun's lifespan?

Accepted Answer

A) The star's lifespan is shorter than that of our Sun. 
B) The star's lifespan is longer than that of our Sun. 
C) The star's lifespan is the same as that of our Sun because mass does not affect the lifetime. 
D) More information is required to answer the question. 
A) The star's lifespan is shorter than that of our Sun. 
B) The star's lifespan is longer than that of our Sun. 
C) The star's lifespan is the same as that of our Sun because mass does not affect the lifetime. 
D) More information is required to answer the question.

Question 10

When a star is just evolving off the main sequence,which element is most common in the core?

Accepted Answer

A) Hydrogen 
B) Helium 
C) Carbon 
D) Iron 
E) Depends on spectral type 
A) Hydrogen 
B) Helium 
C) Carbon 
D) Iron 
E) Depends on spectral type

Question 11

A planetary nebula is produced by

Accepted Answer

A) A supernova explosion 
B) The dust left over when a cluster of stars forms 
C) The gradual loss of its outer layers by a dying star 
D) A nova explosion 
A) A supernova explosion 
B) The dust left over when a cluster of stars forms 
C) The gradual loss of its outer layers by a dying star 
D) A nova explosion

Question 12

What is the triple alpha process?

Accepted Answer

A) A fraternity initiation ceremony 
B) A pair of reactions that fuses helium into carbon 
C) The mechanism that forms triple star systems 
D) A situation in which all three energy transport mechanisms work at once 
A) A fraternity initiation ceremony 
B) A pair of reactions that fuses helium into carbon 
C) The mechanism that forms triple star systems 
D) A situation in which all three energy transport mechanisms work at once

Question 13

Which of the following cannot be assumed about the stars in a given cluster?

Accepted Answer

A) They are all nearly the same distance from us 
B) They all had the same initial chemical composition 
C) They all have the same age 
D) They all have the same mass 
A) They are all nearly the same distance from us 
B) They all had the same initial chemical composition 
C) They all have the same age 
D) They all have the same mass

Question 14

What happens when electrons become degenerate?

Accepted Answer

A) Their pressure becomes independent of temperature 
B) They are converted to neutrons 
C) They become extremely hot 
D) They form a crystalline lattice 
A) Their pressure becomes independent of temperature 
B) They are converted to neutrons 
C) They become extremely hot 
D) They form a crystalline lattice

Question 15

The main sequence lifetime of an O star compared with an M star is

Accepted Answer

A) Much longer because there is more fuel available 
B) Much shorter because the O star burns fuel at a much faster rate. 
C) About the same because all stars live about 10 billion years. 
D) Much shorter because there is much less hydrogen in O stars 
A) Much longer because there is more fuel available 
B) Much shorter because the O star burns fuel at a much faster rate. 
C) About the same because all stars live about 10 billion years. 
D) Much shorter because there is much less hydrogen in O stars

Question 16

A two solar mass star has about 2 times the Sun's supply of nuclear energy.Its luminosity is 10 times that of the Sun.How does the lifetime of the star compare with that of the Sun?

Accepted Answer

A) 2 times longer 
B) The same 
C) One-fifth as long 
D) One-tenth as long 
A) 2 times longer 
B) The same 
C) One-fifth as long 
D) One-tenth as long

Exam 19: The Evolution of Stars

The age of a cluster can be estimated by

Cluster A has no stars of spectral type O,B,and A on its main sequence,whereas cluster B has stars of all types but O on its main sequence.Which of the following correctly describes the relative ages of clusters A and B?

One reason that Cepheid stars are important to astronomers is that

Estimate the main sequence lifetime for a star that is twice as massive as the Sun and 8 times as luminous.

What limits the formation of giant stars of extremely large sizes?

What causes Cepheid variables to vary in brightness?

As soon as its core hydrogen is exhausted,a star like the Sun begins to evolve

Based on your knowledge of the H-R diagram,which of the descriptions of a star cluster is astrophysical nonsense?

The lifetime of a star half the mass of the Sun has what relationship to our Sun's lifespan?

When a star is just evolving off the main sequence,which element is most common in the core?

A planetary nebula is produced by

What is the triple alpha process?

Which of the following cannot be assumed about the stars in a given cluster?

What happens when electrons become degenerate?

The main sequence lifetime of an O star compared with an M star is

A two solar mass star has about 2 times the Sun's supply of nuclear energy.Its luminosity is 10 times that of the Sun.How does the lifetime of the star compare with that of the Sun?

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