Question 1

At what stage of its evolutionary life is the Sun?

Accepted Answer

A)   main sequence, or "middle age"
B)   pre-main sequence, variable star
C)   just before supernova stage (perhaps 5 years) , late evolutionary stage
D)   post-main sequence, red giant (cool)  phase

Question 2

At what stage of evolution are the stars with similar luminosities between 50 and 100 times that of the Sun but spread over a range of temperatures?

Accepted Answer

A)   main-sequence stage because the horizontal-branch region is part of the main sequence
B)   pre-main-sequence stage, evolving toward the main sequence
C)   white dwarf stage
D)   post-main-sequence stage

Question 3

What condition is considered sufficient for an interstellar cloud to collapse and form a star or stars (i.e., if this condition holds then the cloud has to collapse) ?

Accepted Answer

A)   The cloud must be alone in space (far from stars and other interstellar clouds) .
B)   Gravity must dominate gas pressure inside the cloud.
C)   Gravity must be strong enough to reach all parts of the cloud.
D)   The cloud must be cooler than 100 K.

Question 4

Cepheid stars are

Accepted Answer

A)   giant stars that pulsate in brightness, size, and temperature.
B)   white dwarf stars late in their evolutionary life.
C)   members of binary systems in which one star periodically eclipses the other.
D)   stars at an early stage in stellar evolution, pre-main-sequence.

Question 5

The present estimate of the age of the universe is about 14 billion years. How long will a half-solar-mass star spend on the main sequence, compared with the present age of the universe?

Accepted Answer

A)   about 3 times the age of the universe
B)   more than 10 times the age of the universe
C)   less than 1/10 of the age of the universe
D)   about 1/2 of the age of the universe

Question 6

When plotted on an H-R diagram, the more massive stars of a particular star cluster are on the main sequence and the less massive stars are above the main sequence. Can the age of this cluster be determined? (In other words, how long is it since these stars condensed from the interstellar medium?)

Accepted Answer

A)   Yes, by finding the most massive star that is on the main sequence. The age of the cluster equals the time this star spent as a protostar.
B)   No.
C)   Yes, by finding the least massive protostar. The age of the cluster equals the time this star took to reach the main sequence.
D)   Yes, by finding the least massive star on the main sequence. The age of the cluster equals the time this star spent as a protostar.

Question 7

The Horsehead Nebula in Orion (see Figure 13-5 in the text)  is a distinct dark region surrounded by brighter regions. The Horsehead is an example of

Accepted Answer

A)   an emission nebula.
B)   a black hole.
C)   a Bok gobule.
D)   a dark nebula.

Question 8

What happens to the luminosity of a low-mass star as it passes through a helium flash?

Accepted Answer

A)   The luminosity, which was increasing slowly before the helium flash, suddenly brightens by several orders of magnitude.
B)   The luminosity, which was decreasing slowly before the helium flash, suddenly brightens by several orders of magnitude.
C)   The helium flash affects only the core. The luminosity of the star remains unchanged for a long time after the flash.
D)   The luminosity, which was rising before the helium flash, drops quickly after the helium flash.

Question 9

What is the Pauli exclusion principle?

Accepted Answer

A)   Photons of less than a certain wavelength cannot eject electrons from a metal.
B)   Two identical particles cannot occupy the same place at the same time.
C)   Two different atoms cannot have the same energy levels.
D)   Two identical photons cannot be absorbed by the same atom.

Question 10

What is the MOST important property of a star that governs its evolution and lifetime?

Accepted Answer

A)   mass
B)   surface temperature
C)   abundance of heavy elements
D)   speed of rotation

Question 11

Why does the Hertzsprung-Russell diagram of a globular cluster NOT contain any stars with high luminosity and high temperature on the main sequence?

Accepted Answer

A)   These high-mass stars evolved away from the main sequence long ago.
B)   Stars that will occupy this position on the main sequence have not yet evolved there from the protostar stage.
C)   The stars that were in this position on the main sequence have undergone splitting into binary stars and hence appear lower down on the diagram.
D)   This type of cluster contains only low-mass stars and has never had high-luminosity stars on its main sequence.

Question 12

Which of these astronomical objects or systems is likely to be the oldest?

Accepted Answer

A)   T Tauri star
B)   Pleiades
C)   Sun
D)   globular cluster

Question 13

What are the main general features that make clusters of stars useful to astronomers?

Accepted Answer

A)   The stars all have the same apparent magnitude, the same surface temperatures, and the same sizes.
B)   The stars are all at the same distance from Earth, have the same surface temperature, and joined the cluster at various times.
C)   The stars all have the same intrinsic brightness but differ in size and surface temperature.
D)   The stars are at the same distance from Earth, were formed at approximately the same time, and were made from the same chemical mix.

Question 14

What particular and very important phenomenon frequently occurs in binary star systems where the stars are very close together?

Accepted Answer

A)   The radiation from the hotter star slowly heats and evaporates away the cooler star.
B)   Mass lost from one star is deposited on its companion.
C)   The less massive star, in its elliptical orbit, repeatedly passes through the thin, extended atmosphere of the second star, producing periodic rises and falls in light output from the star system.
D)   The less massive star spirals slowly into its more massive companion because of tidal interactions.

Question 15

The Cygnus Loop Nebula is characterized by having an arched, shell-like appearance. The Cygnus Loop is a

Accepted Answer

A)   dark nebula.
B)   reflection nebula.
C)   supernova remnant.
D)   giant molecular cloud.

Question 16

If a protostar were able to contract (get smaller)  without any change in its surface temperature, what would happen to its luminosity?

Accepted Answer

A)   It is not possible to predict the change in the protostar's luminosity since other factors are involved.
B)   The star's luminosity would increase due to the compression of the gas.
C)   The star's luminosity would decrease due to the reduced surface area of the protostar.
D)   The star's luminosity would remain the same since the temperature does not change.

Question 17

What is the "safety valve" that operates in normal (nondegenerate)  stars?

Accepted Answer

A)   If thermonuclear reactions proceed too quickly, the star runs out of fuel before anything drastic happens.
B)   If the stellar gas is suddenly heated, it expands and cools.
C)   If the star gets too big, it collapses into a black hole.
D)   If the pressure becomes too high, electrons combine with protons to relieve the pressure.

Question 18

Why is it that the majority of stars in the sky are in the main-sequence phase of their lives?

Accepted Answer

A)   Most stars die at the end of the main-sequence phase.
B)   The main-sequence phase is the longest-lasting phase in each star's life.
C)   The main-sequence phase is the only phase that is common to all stars.
D)   Most stars in the sky were created at about the same time, so these are all in the same phase of their lives.

Question 19

The study of stars in clusters has especially helped astronomers to understand

Accepted Answer

A)   stellar evolution, the development of stars with time.
B)   the mechanism of mass loss in stars.
C)   the reason for differences in surface temperatures of stars.
D)   the action of nuclear fusion in stars.

Question 20

How have complex molecules such as formaldehyde (H2CO)  been detected in interstellar clouds?

Accepted Answer

A)   by direct sampling by space probes
B)   by observing the chemical reactions in which they are created
C)   only by theoretical modeling since it is known that the component elements (H, C, O)  are present in space
D)   by molecular emission lines

Exam 13: The Lives of Stars From Birth Through Middle Age

The Cygnus Loop Nebula is characterized by having an arched, shell-like appearance. The Cygnus Loop is a

Correct AnswerverifiedShow Answer

What condition is considered sufficient for an interstellar cloud to collapse and form a star or stars (i.e., if this condition holds then the cloud has to collapse) ?

Correct AnswerverifiedShow Answer

What particular and very important phenomenon frequently occurs in binary star systems where the stars are very close together?

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The study of stars in clusters has especially helped astronomers to understand

Correct AnswerverifiedShow Answer

What happens to the luminosity of a low-mass star as it passes through a helium flash?

Correct AnswerverifiedShow Answer

Which of these astronomical objects or systems is likely to be the oldest?

Correct AnswerverifiedShow Answer

What is the Pauli exclusion principle?

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Why does the Hertzsprung-Russell diagram of a globular cluster NOT contain any stars with high luminosity and high temperature on the main sequence?

Correct AnswerverifiedShow Answer

When plotted on an H-R diagram, the more massive stars of a particular star cluster are on the main sequence and the less massive stars are above the main sequence. Can the age of this cluster be determined? (In other words, how long is it since these stars condensed from the interstellar medium?)

Correct AnswerverifiedShow Answer

How have complex molecules such as formaldehyde (H2CO) been detected in interstellar clouds?

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The present estimate of the age of the universe is about 14 billion years. How long will a half-solar-mass star spend on the main sequence, compared with the present age of the universe?

Correct AnswerverifiedShow Answer

What is the MOST important property of a star that governs its evolution and lifetime?

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The Horsehead Nebula in Orion (see Figure 13-5 in the text) is a distinct dark region surrounded by brighter regions. The Horsehead is an example of

Correct AnswerverifiedShow Answer

Cepheid stars are

Correct AnswerverifiedShow Answer

Why is it that the majority of stars in the sky are in the main-sequence phase of their lives?

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At what stage of its evolutionary life is the Sun?

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At what stage of evolution are the stars with similar luminosities between 50 and 100 times that of the Sun but spread over a range of temperatures?

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What is the "safety valve" that operates in normal (nondegenerate) stars?

Correct AnswerverifiedShow Answer

What are the main general features that make clusters of stars useful to astronomers?

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If a protostar were able to contract (get smaller) without any change in its surface temperature, what would happen to its luminosity?

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How have complex molecules such as formaldehyde (H₂CO) been detected in interstellar clouds?

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