Question 1

What wavelengths have astronomers used to map and study the distribution of the giant molecular clouds in space?

Accepted Answer

A)   X-ray
B)   visible
C)   ultraviolet
D)   radio

Question 2

What rates of mass loss from red giant stars are typical?

Accepted Answer

A)   10-¹⁴ solar mass per year
B)   10-³ solar mass per year
C)   Red giant stars do not suffer mass loss.
D)   10-⁷ solar mass per year

Question 3

The transfer of mass from the surface of one star onto the surface of another is MOST often observed in _____ binaries.

Accepted Answer

A)   detached
B)   overcontact
C)   contact
D)   semidetached

Question 4

A T Tauri star is at what stage of its stellar evolution?

Accepted Answer

A)   just before red giant phase, when variability begins
B)   well established on the main sequence
C)   the end of its life, decaying away and cooling
D)   protostar, before the main-sequence phase

Question 5

Which factor,more than any other,modifies the evolutionary tracks of stars in binary combinations compared with their single-star counterparts?

Accepted Answer

A)   tidal distortion of the shapes of the stars
B)   reduction of the quantum mechanical limitation on continued shrinking of one star by the gravitational field of the second star
C)   mass exchange between the stars
D)   radiation from one star heating the surface of the second star

Question 6

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 7

What is the dominant nuclear reaction during helium burning in the core of a star?

Accepted Answer

A)   ¹H + ⁴He combine to form C,
B)   ⁴He fuses to form C.
C)   ²He fuses to form C.
D)   ³He fuses to form C.

Question 8

What event occurs at the end of the protostar stage of a star's life?

Accepted Answer

A)   The star explodes, forming a supernova remnant.
B)   Gas is spun off from the star's equator, from which planets may form.
C)   Nuclear reactions begin in the star's core, converting hydrogen into helium.
D)   The star begins a long period of contraction in which gravitational energy is converted into heat.

Question 9

A main-sequence star is defined as a star:

Accepted Answer

A)   with a surface temperature equal to that of the Sun.
B)   in which nuclear fusion reactions generate sufficient energy to oppose further condensation of the star.
C)   whose age after birth is about 1 million years.
D)   with a luminosity precisely equal to that of the Sun.

Question 10

In terms of nuclear reactions,what is the next stage of a star's life after the end of hydrogen burning in the core?

Accepted Answer

A)   hydrogen burning in a thin shell around the core
B)   helium burning in the core
C)   carbon burning
D)   death (it becomes either a supernova or a white dwarf)

Question 11

How is the length of a star's lifetime related to the mass of the star?

Accepted Answer

A)   Lower-mass stars run through their lives faster and have shorter lifetimes.
B)   The lifetimes of stars are too long to measure, so it is not known how (or if)  their lifetimes depend on mass.
C)   A star's lifetime does not depend on its mass.
D)   Higher-mass stars run through their lives faster and have shorter lifetimes.

Question 12

An astronomer plots the H-R diagram of a star cluster and finds that it contains hot B-type stars on the main sequence and cooler G- and K-type stars noticeably above the main sequence.This cluster is:

Accepted Answer

A)   of indeterminate age since the age of the cluster cannot be estimated from the information given.
B)   impossible because cool stars cannot be above the main sequence when hot stars are on the main sequence.
C)   old because the G and K stars are already evolving off (away from)  the main sequence.
D)   very young because the G and K stars are still evolving toward the main sequence.

Question 13

Stars are formed from interstellar matter.Why then are stars in open clusters metal-rich,while stars in globular clusters are metal-poor?

Accepted Answer

A)   Open clusters contain very hot stars that produce metals by nuclear reactions in their outer layers.
B)   Globular clusters have "burned" their heavy elements over their longer lifetime.
C)   Globular clusters are too young for their stars to have produced any significant amount of metals.
D)   Open clusters are young and stars have formed from material that has been enriched in metals by supernova explosions of previous stars.

Question 14

The H-R diagram for an open cluster gives special information because all stars in an open cluster are:

Accepted Answer

A)   the same age.
B)   the same mass.
C)   moving in the same direction.
D)   the same spectral type.

Question 15

What fraction of the mass of a typical interstellar cloud is helium?

Accepted Answer

A)   50%
B)   2%
C)   10%
D)   25%

Question 16

If the universe is only 14 billion years old,which stars have never moved beyond the main sequence?

Accepted Answer

A)   stars with masses less than 0.08 solar mass
B)   stars with masses less than 0.75 solar mass
C)   stars with masses greater than 100 solar masses
D)   stars with masses greater than 10 solar masses

Question 17

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 18

MOST of the energy emitted by a protostar comes from:

Accepted Answer

A)   radioactive elements.
B)   gravitational potential energy being converted to heat as the protostar collapses.
C)   infalling material colliding with the protostar's surface.
D)   nuclear fusion.

Question 19

What is the SECOND most abundant element in the universe (after hydrogen) ?

Accepted Answer

A)   helium
B)   carbon
C)   nitrogen
D)   iron

Question 20

If you look out in the night sky with your naked eye,what is the luminosity class of most of the stars you see? Are these actually the most numerous stars?

Accepted Answer

A)   You will see mostly main-sequence stars; yes, these are the most numerous of stars.
B)   You will see mostly main-sequence stars, but most stars are actually giants.
C)   You will see mostly giants, but most stars are actually main-sequence stars.
D)   You will see mostly giants; yes, most stars are actually giants.

Exam 11: The Lives of the Stars From Birth Through Middle Age

In terms of nuclear reactions,what is the next stage of a star's life after the end of hydrogen burning in the core?

Correct AnswerverifiedShow Answer

An astronomer plots the H-R diagram of a star cluster and finds that it contains hot B-type stars on the main sequence and cooler G- and K-type stars noticeably above the main sequence.This cluster is:

Correct AnswerverifiedShow Answer

Stars are formed from interstellar matter.Why then are stars in open clusters metal-rich,while stars in globular clusters are metal-poor?

Correct AnswerverifiedShow Answer

The H-R diagram for an open cluster gives special information because all stars in an open cluster are:

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What event occurs at the end of the protostar stage of a star's life?

Correct AnswerverifiedShow Answer

A T Tauri star is at what stage of its stellar evolution?

Correct AnswerverifiedShow Answer

If the universe is only 14 billion years old,which stars have never moved beyond the main sequence?

Correct AnswerverifiedShow Answer

If you look out in the night sky with your naked eye,what is the luminosity class of most of the stars you see? Are these actually the most numerous stars?

Correct AnswerverifiedShow Answer

What is the dominant nuclear reaction during helium burning in the core of a star?

Correct AnswerverifiedShow Answer

How is the length of a star's lifetime related to the mass of the star?

Correct AnswerverifiedShow Answer

Which factor,more than any other,modifies the evolutionary tracks of stars in binary combinations compared with their single-star counterparts?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

A main-sequence star is defined as a star:

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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What rates of mass loss from red giant stars are typical?

Correct AnswerverifiedShow Answer

MOST of the energy emitted by a protostar comes from:

Correct AnswerverifiedShow Answer

The transfer of mass from the surface of one star onto the surface of another is MOST often observed in _____ binaries.

Correct AnswerverifiedShow Answer

What fraction of the mass of a typical interstellar cloud is helium?

Correct AnswerverifiedShow Answer

What is the SECOND most abundant element in the universe (after hydrogen) ?

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What wavelengths have astronomers used to map and study the distribution of the giant molecular clouds in space?

Correct AnswerverifiedShow Answer

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