Question 1

How does the quantity of gravitational force on a binary companion change when a 6-solar-mass star becomes a 6-solar-mass black hole?

Accepted Answer

A)   It increases.
B)   It decreases.
C)   It remains the same.
D)   It is impossible to determine.

Question 2

The pulsed nature of the radiation at all wavelengths that is seen to come from a pulsar is produced by the

Accepted Answer

A)   mutual orbiting and eclipsing of two very hot stars in a close binary system.
B)   rapid pulsation in size and hence brightness of a small white-dwarf star.
C)   rapid rotation of a neutron star that is producing two oppositely directed beams of radiation.
D)   extremely hot matter that is rapidly orbiting a black hole just prior to descending into it. C

Question 3

What feature distinguishes a black hole from all other objects in the universe?

Accepted Answer

A)   It emits large quantities of X-rays.
B)   The escape velocity from this object is greater than the speed of light.
C)   The shape of its gravitational field is always different from that of an ordinary massive object,even at large distances from it.
D)   Its total mass exceeds 3 solar masses.

Question 4

Which nuclear fusion cycle follows the helium fusion phase as a massive star evolves?

Accepted Answer

A)   Silicon "burning"
B)   Carbon "burning"
C)   Iron "burning"
D)   Oxygen "burning"

Question 5

The "guest star" that appeared in 1054 was seen

Accepted Answer

A)   in China.
B)   in Constantinople.
C)   by Anasazi in the current U.S.Southwest.
D)   All of these D

Question 6

What is a pulsar?

Accepted Answer

A)   A pulsating white-dwarf star,fluctuating rapidly in brightness
B)   A rapidly rotating neutron star,producing beams of radio energy and in some cases,light and X-rays
C)   A rotating black hole,producing two jets of gas in opposite directions and pulses of gravitational energy
D)   A Cepheid variable star with a period of a few days

Question 7

Type Ia supernovae are generally brighter than Type II supernovae.

Accepted Answer

A) True 
 B)False

Question 8

One object that is believed to be a black hole in our Galaxy is

Accepted Answer

A)   the central star in the Ring Nebula in Lyra.
B)   the central star in the Crab Nebula.
C)   the undetected tenth planet in our solar system,whose presence has been inferred from its gravitational influence on the outer planets.
D)   Cygnus X-1,a powerful X-ray source.

Question 9

During the late stages of evolution (e.g. ,oxygen burning) in massive stars,nuclear reactions produce many free neutrons.What very important effect do these neutrons have on the composition of the star?

Accepted Answer

A)   The neutrons,being uncharged,escape from the star,thus carrying away energy from the core of the star and lowering its temperature.
B)   The neutrons are captured by atomic nuclei and can produce heavy elements that would not form from nuclear fusion alone.
C)   The neutrons are captured by atomic nuclei,causing the nuclei to split by fission reactions into lighter elements that would otherwise be very rare in the universe.
D)   The neutrons decay into protons and electrons,thus increasing the amount of hydrogen in the core and extending the life of the star.

Question 10

What is the Schwarzschild radius of a black hole?

Accepted Answer

A)   The radius of the singularity
B)   The distance from the singularity to the point from which the X-rays are emitted
C)   The maximum distance from the singularity from which nothing can escape from the black hole
D)   The distance from the singularity to the point where any object entering the black hole will gain energy before leaving again

Question 11

Stars with masses between 8 and 14 times the mass of the Sun will end their lives as neutron stars.

Accepted Answer

A) True 
 B)False

Question 12

If a star ended its main-sequence life with about 5.1 solar masses,the remnant would likely be a

Accepted Answer

A)   white dwarf.
B)   neutron star.
C)   black hole.
D)   None of these

Question 13

Black holes are so named because

Accepted Answer

A)   they emit a perfect blackbody spectrum.
B)   no light or any other electromagnetic radiation can escape from inside them.
C)   all their electromagnetic radiation is gravitationally redshifted to the infrared,which leaves no light in the optical region.
D)   they emit no visible light,their only spectral lines are in the radio and infrared.

Question 14

The event horizon surrounding a black hole describes the "surface" in space where the escape velocity equals the speed of light.

Accepted Answer

A) True 
 B)False

Question 15

Can a white dwarf explode?

Accepted Answer

A)   Only if another star collides with it;stars are so far apart in space that this is unlikely ever to have happened in our Galaxy.
B)   Yes,but only if nuclear reactions in the white dwarf core reach the stage of silicon burning,producing iron.
C)   No,white dwarfs are held up by electron degeneracy pressure,and this configuration is stable against collapse or explosion.
D)   Yes,but only if it is in a binary star system.

Question 16

In 1054,the imperial astronomer to the Chinese court recorded observing a "guest star" in the sky.We know now that this "guest star" was a supernova explosion within our Galaxy.

Accepted Answer

A) True 
 B)False

Question 17

A graph of the brightness of a supernova versus time is known as a(n)

Accepted Answer

A)   light curve.
B)   H-R Diagram.
C)   radial velocity curve.
D)   Schwartzschild graph.

Question 18

The diameter of a typical neutron star of 1 solar mass is predicted to be approximately

Accepted Answer

A)   1 km.
B)   that of the Sun.
C)   that of an average city,about 30 km.
D)   that of Earth,12,800 km.

Question 19

How do pulsars change over time?

Accepted Answer

They tend to slow down over time because they are radiating away their rotational energy and its pulse period increases.However,if they are in a binary system,they can have interactions that cause them to spin up.

Question 20

Which of the following is NEVER a consequence of a supernova explosion?

Accepted Answer

A)   Condensation of matter into a solid nuclear star composed entirely of neutrons
B)   Triggering of star formation by shock waves moving through interstellar space
C)   Formation of a planetary nebula
D)   Manufacture of the nuclei of heavy elements

Exam 12: Predicting the Violent End of the Largest Stars

How does the quantity of gravitational force on a binary companion change when a 6-solar-mass star becomes a 6-solar-mass black hole?

Correct AnswerverifiedShow Answer

The pulsed nature of the radiation at all wavelengths that is seen to come from a pulsar is produced by the

Correct AnswerverifiedC

What feature distinguishes a black hole from all other objects in the universe?

Correct AnswerverifiedShow Answer

Which nuclear fusion cycle follows the helium fusion phase as a massive star evolves?

Correct AnswerverifiedShow Answer

The "guest star" that appeared in 1054 was seen

Correct AnswerverifiedD

What is a pulsar?

Correct AnswerverifiedShow Answer

Type Ia supernovae are generally brighter than Type II supernovae.

Correct AnswerverifiedShow Answer

One object that is believed to be a black hole in our Galaxy is

Correct AnswerverifiedShow Answer

During the late stages of evolution (e.g. ,oxygen burning) in massive stars,nuclear reactions produce many free neutrons.What very important effect do these neutrons have on the composition of the star?

Correct AnswerverifiedShow Answer

What is the Schwarzschild radius of a black hole?

Correct AnswerverifiedShow Answer

Stars with masses between 8 and 14 times the mass of the Sun will end their lives as neutron stars.

Correct AnswerverifiedShow Answer

If a star ended its main-sequence life with about 5.1 solar masses,the remnant would likely be a

Correct AnswerverifiedShow Answer

Black holes are so named because

Correct AnswerverifiedShow Answer

The event horizon surrounding a black hole describes the "surface" in space where the escape velocity equals the speed of light.

Correct AnswerverifiedShow Answer

Can a white dwarf explode?

Correct AnswerverifiedShow Answer

In 1054,the imperial astronomer to the Chinese court recorded observing a "guest star" in the sky.We know now that this "guest star" was a supernova explosion within our Galaxy.

Correct AnswerverifiedShow Answer

A graph of the brightness of a supernova versus time is known as a(n)

Correct AnswerverifiedShow Answer

The diameter of a typical neutron star of 1 solar mass is predicted to be approximately

Correct AnswerverifiedShow Answer

How do pulsars change over time?

Correct AnswerverifiedThey tend to slow down over time because they are radiating away their rotational energy and its pulse period increases.However,if they are in a binary system,they can have interactions that cause them to spin up.

Which of the following is NEVER a consequence of a supernova explosion?

Correct AnswerverifiedShow Answer

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C

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D

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They tend to slow down over time because they are radiating away their rotational energy and its pulse period increases.However,if they are in a binary system,they can have interactions that cause them to spin up.

Correct Answer
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