Question 1

Most interstellar matter is too cold to be observed optically.Its radiation can be detected in which part of the electromagnetic spectrum?

Accepted Answer

A)   gamma-ray
B)   ultraviolet
C)   infrared
D)   X-ray

Question 2

What scientific method is used to observe the pulsation in size of a Cepheid variable star?

Accepted Answer

A)   This behavior has only been predicted theoretically; it has never been detected.
B)   observed perturbations in the orbits of planets around the star
C)   observed increase and decrease in the size of the star's image
D)   Doppler shift of absorption lines in the star's spectrum

Question 3

The apparent reddening of light from stars after its passage through the interstellar medium (ISM) is caused by:

Accepted Answer

A)   the additional contribution to this starlight by emission from hydrogen gas in the ISM.
B)   preferential scattering of blue starlight by fine dust grains.
C)   Zeeman shift of the light by the powerful magnetic fields existing within the ISM.
D)   scattering of this light from rapidly moving material; the light is Doppler-shifted toward the red end of the spectrum.

Question 4

Comparing Population I and Population II stars,the stars that formed first after the initial Big Bang were:

Accepted Answer

A)   virtually all Population I stars.
B)   virtually all Population II stars.
C)   about the same mixture of Population I and Population II stars that we now observe.
D)   of an entirely different type that has since evolved into Population I and Population II.

Question 5

When does a star achieve static equilibrium?

Accepted Answer

A)   When it becomes a main-sequence star.
B)   When it leaves the main sequence.
C)   When it becomes a protostar.
D)   This question has different answers for stars of different masses. Massive stars never achieve equilibrium; small stars achieve hydrostatic equilibrium as soon as they reach the main sequence.

Question 6

What does the term hydrostatic equilibrium mean in reference to stars?

Accepted Answer

A)   The pressure throughout a star is constant.
B)   The pressure within a star is sufficient to cause the star to expand at a constant rate.
C)   The gravitational force within a star is sufficient to cause the star to collapse inward at a steady rate.
D)   Each layer within a star is in balance with respect to pressure and gravity.

Question 7

Suppose that an astronomy news item announces the discovery of a brown dwarf.What is it that has been discovered?

Accepted Answer

A)   a prestellar object undergoing gravitational collapse
B)   a Pluto-like object in the Kuiper belt, beyond the edge of the planetary system
C)   an object too large to be a planet but too small to be a star
D)   a protostar still embedded in the cloud of gas and dust from which it formed

Question 8

The light from a distant cloud of gas and dust looks distinctly red to the unaided eye.When a spectrum is taken,the short wavelengths are all found to be dimmed in intensity compared with the longer wavelengths,which are all more intense.Thus,the red color in this situation is due to:

Accepted Answer

A)   interstellar reddening.
B)   the Balmer spectrum of hydrogen.
C)   the Doppler effect.
D)   any one of these three phenomena.

Question 9

The space between stars is known to contain:

Accepted Answer

A)   large quantities of dust that absorb and scatter light but no gas, either atomic or molecular.
B)   variable amounts of gas but no dust, which forms only in planetary systems near stars.
C)   a perfect vacuum.
D)   gas, both atomic and molecular, and dust.

Question 10

A main-sequence star can be no smaller than 0.08 solar mass.The reason is that:

Accepted Answer

A)   thermonuclear reactions begin so suddenly in stars of less than 0.08 solar mass that the star is disrupted by an explosion.
B)   protostars of less than 0.08 solar mass cannot form.
C)   protostars of less than 0.08 solar mass are not massive enough to contract.
D)   the temperature in a contracting protostar of less than 0.08 solar mass does not become high enough for nuclear reactions to start.

Question 11

Star formation takes place in:

Accepted Answer

A)   giant molecular clouds.
B)   globular clusters.
C)   blue reflection nebulae.
D)   hot, turbulent gas thrown out in a supernova explosion.

Question 12

The period of variability of a Cepheid variable star,which is easily measured,is directly related to which stellar parameter,thereby providing a reliable method for the measurement of distance to stars?

Accepted Answer

A)   luminosity
B)   velocity away from Earth
C)   surface temperature
D)   surface magnetic field

Question 13

Parts of a supernova remnant become visible:

Accepted Answer

A)   because of radioactive elements that were created in the supernova and carried along with the remnant.
B)   when large hot stars form within the gas and dust of the remnant and emit radiation which excites the remaining gas.
C)   when they collide with other clouds of gas and dust.
D)   when they interact with the galaxy's strong magnetic field.

Question 14

If we plotted the stars in a young star cluster on a Hertzsprung-Russell diagram,we would expect to see:

Accepted Answer

A)   all the stars on the main sequence.
B)   the more massive stars above the main sequence and the less massive stars on the main sequence.
C)   some stars on the main sequence and others above the main sequence, in random fashion depending on when each star condensed from the interstellar cloud.
D)   the more massive stars on the main sequence and the less massive stars above the main sequence.

Question 15

Which common molecule found in interstellar space contains nitrogen atoms but no oxygen?

Accepted Answer

A)   water vapor (H₂O) 
B)   formaldehyde (H₂CO) 
C)   methane (CH₄) 
D)   ammonia (NH₃)

Question 16

Which mechanism is thought to be ineffective and inefficient in the triggering of star birth in molecular clouds?

Accepted Answer

A)   gravitational contraction of a hot gas cloud
B)   collisions between two interstellar clouds
C)   supernova explosions and the resultant shock waves
D)   radiation pressure from the intense UV radiation from hot stars

Question 17

The bright stars at the center of an emission nebula (H II region) are:

Accepted Answer

A)   young O and B stars.
B)   red supergiants.
C)   hot white dwarfs.
D)   T Tauri stars.

Question 18

What makes a red giant star so large?

Accepted Answer

A)   The helium-rich core has expanded, pushing the outer layers of the star outward.
B)   The hydrogen-burning shell is heating the envelope and making it expand.
C)   Red giants are rapid rotators, and centrifugal force pushes the surface of the star outward.
D)   The star has many times more mass than the Sun.

Question 19

In which region of the Hertzsprung-Russell diagram does a newly formed protostar first appear when it begins to shine at visible wavelengths?

Accepted Answer

A)   the bottom right corner; very low luminosity because it is both small and cool
B)   the center of the main sequence since all protostars begin their lives at this position and move up or down it depending on their mass as time passes
C)   the right side; relatively large luminosity because of its size but cool
D)   the top left corner; at the top of the main sequence, down which it will progress with time

Question 20

During helium burning,some ⁴He combines with ¹⁶O,much like the way it combines with ¹²C to form ¹⁶O.What is produced by the ¹⁶O + ⁴He reaction? (The periodic table shown Appendix E of Comins,Discovering the Essential Universe,6th ed.,may be useful.)

Accepted Answer

A)   ¹⁸O (heavy isotope of oxygen) 
B)   ²⁰Ne (regular isotope of neon) 
C)   ²²Na (light isotope of sodium) 
D)   ²⁰F (heavy isotope of fluorine)

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

If we plotted the stars in a young star cluster on a Hertzsprung-Russell diagram,we would expect to see:

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Which mechanism is thought to be ineffective and inefficient in the triggering of star birth in molecular clouds?

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In which region of the Hertzsprung-Russell diagram does a newly formed protostar first appear when it begins to shine at visible wavelengths?

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What does the term hydrostatic equilibrium mean in reference to stars?

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Star formation takes place in:

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Parts of a supernova remnant become visible:

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The apparent reddening of light from stars after its passage through the interstellar medium (ISM) is caused by:

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A main-sequence star can be no smaller than 0.08 solar mass.The reason is that:

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Which common molecule found in interstellar space contains nitrogen atoms but no oxygen?

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The light from a distant cloud of gas and dust looks distinctly red to the unaided eye.When a spectrum is taken,the short wavelengths are all found to be dimmed in intensity compared with the longer wavelengths,which are all more intense.Thus,the red color in this situation is due to:

Correct AnswerverifiedShow Answer

The period of variability of a Cepheid variable star,which is easily measured,is directly related to which stellar parameter,thereby providing a reliable method for the measurement of distance to stars?

Correct AnswerverifiedShow Answer

The bright stars at the center of an emission nebula (H II region) are:

Correct AnswerverifiedShow Answer

Comparing Population I and Population II stars,the stars that formed first after the initial Big Bang were:

Correct AnswerverifiedShow Answer

When does a star achieve static equilibrium?

Correct AnswerverifiedShow Answer

Suppose that an astronomy news item announces the discovery of a brown dwarf.What is it that has been discovered?

Correct AnswerverifiedShow Answer

The space between stars is known to contain:

Correct AnswerverifiedShow Answer

Most interstellar matter is too cold to be observed optically.Its radiation can be detected in which part of the electromagnetic spectrum?

Correct AnswerverifiedShow Answer

During helium burning,some ⁴He combines with ¹⁶O,much like the way it combines with ¹²C to form ¹⁶O.What is produced by the ¹⁶O + ⁴He reaction? (The periodic table shown Appendix E of Comins,Discovering the Essential Universe,6th ed.,may be useful.)

Correct AnswerverifiedShow Answer

What scientific method is used to observe the pulsation in size of a Cepheid variable star?

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What makes a red giant star so large?

Correct AnswerverifiedShow Answer

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